sellecting cylinder heads



sellecting cylinder heads

Postby grumpyvette » November 26th, 2008, 11:26 am

READ THIS THREAD AND LINKs and SUB LINKS AS ITS IMPORTANT TO UNDERSTANDING SOME FACTORS, and theres a ton of useful info in the links

read these threads and sub-links also, as they contain good info, if you fail to read thru the sub links youll miss a ton of useful info, don,t think published flow numbers or price alone are the only really useful factors to use, remember a flow bench has very little in common with a running engine
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most stock and some aftermarket heads benefit from port and bowl clean up work,to smooth and increase flow rates ,port throats generally run 80%-85% of total valve diameter because you need to maintain sufficient valve seat contact area to allow sealing and cooling and some wear during operation
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PORT MATCHING THE INTAKE RUNNER EXIT TO THE CYLINDER HEAD PORT ENTRANCE USUALLY HELPS REDUCE RESTRICTIONS TO FLOW RATES, AND REDUCES FUEL/AIR DISTRIBUTION ISSUES

you might want to watch this 4 part video
http://www.summitracing.com/parts/drt-127422
you should read the links they contain a wealth of info


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USE THE CALCULATORS to match port size to intended rpm levels... but keep in mind valve lift and port flow limitations[/color]

http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
http://www.profilerperformance.com/raci ... -23-degree

viewtopic.php?f=52&t=92

viewtopic.php?f=52&t=10602&p=45479#p45479

http://users.erols.com/srweiss/tablehdc ... _Big_Block

http://www.wallaceracing.com/area-under-curve.php

viewtopic.php?f=55&t=624&p=8692&hilit=volumetric#p8692

viewtopic.php?f=52&t=389&p=7266#p7266

viewtopic.php?f=52&t=731&p=1539#p1539

viewtopic.php?f=52&t=5364&p=16066#p16066

viewtopic.php?f=52&t=266&p=322&hilit=215cc+vortec#p322

A VIDEO DART VS 882 chevy heads TO WATCH
http://www.youtube.com/watch?annotation ... v3ZkqZiMjI

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measuring throat cross sectional area

viewtopic.php?f=52&t=324

viewtopic.php?f=52&t=727

http://racingfeed.com/downloads/chevy_flow_data.pdf

viewtopic.php?f=52&t=410&p=1907#p1907

http://www.profilerperformance.com/sbc-heads-176.html

http://www.airflowresearch.com/articles ... 5/A-P1.htm

http://www.airflowresearch.com/articles ... /A6-P1.htm

http://www.brodix.com/heads/compression.html

http://www.airflowresearch.com/chp_test.php

as you can see in this chart, below most of the stock heads don,t flow as well as the AFR 195cc heads and there ARE better flowing heads, but keep in mind the stock heads were never designed as race components, in most cases the engineers were more concerned with cost and low and mid range speed & torque

I thought I post these flow numbers on ported vortec heads ive seen posted , just in case anyone has ever wondered or wanted to know the flow numbers a set of stock vortecs. I was also curious if any of you have any guesses on what gains I picked up on the port work.
INTAKE LIFT------- STOCK---- PORTED-- GAIN
.1---------- 59--------- 64--------- +5
.2---------- 117------- 132------- +15
.3---------- 170------- 187------- +17
.4---------- 214------- 236------- +22
.5---------- 226------- 255------- +29
.6---------- 219------- 259------- +40
EXHAUST
LIFT STOCK PORTED GAIN
.1---------- 42----------46--------- +4
.2---------- 83----------90--------- +7
.3---------- 123--------139--------+16
.4---------- 136--------161--------+25
.5---------- 143--------174--------+31
.6-----------147------- 178--------+31
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http://www.circletrack.com/enginetech/c ... index.html

http://www.enginebuildermag.com/Article ... tions.aspx

http://www.trickflow.com/media/pdfs/buy ... e_2009.pdf

viewtopic.php?f=52&t=333&p=407#p407

bbc oval ports making 697hp
http://www.popularhotrodding.com/tech/0 ... /dyno.html

heres some guides but keep in mind its NOT the port volume or PORT CCs of total port volume your concerned with, its the port cross sectional area, at its narrow point, you cam timing, compression and displacement, combined with the cars gearing, intake design and exhaust scavenging combined that makes the port size you select work
it does absolutely no good to place a cylinder head with with a port cross sectional area thats larger than the intake port that feeds it, in a combo as all the abrupt increase in port cross section does is cause increased turbulence, and a sudden loss of port air flow speed and that tends to cause fuel to drop out of the airflow or at least disrupt is even distribution
in an ideal world ports reduce cross sectional area bye about 3%-5% from entrance to the valve pocket, and the port cross section in the heads a bit smaller than the intake runner.
cams need to be selected with the engines intended rpm range and power band and the displacement of the engine, plus the engines compression ratio and drive train gearing taken into account, any increase in port cross sectional area above whats required to fill the cylinders in the intended power band tends to reduce efficiency.

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AS your displacement per cylinder increases the effective valve size per cubic inch decreases so you need a slightly tighter LSA and these charts should help.

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so any time you want to stop guessing at the answers, or taking your Buddy,s best guess as a fact, you can use known values & calculations to arrive at valid answers and actually match components



viewtopic.php?f=52&t=322


viewtopic.php?f=52&t=333

http://www.brodix.com/media/images/page_2.jpg

viewtopic.php?f=69&t=1040&hilit=206cc

http://www.corvetteflorida.com/forums/s ... hp?t=17250

http://www.rehermorrison.com/techtalk/06.htm

http://www.gmhightechperformance.com/te ... index.html

http://www.gofastnews.com/board/technic ... lumes.html

one factor that gets discussed a great deal is the difference in port size or port CCs, the sad truth is that Id bet 90% of the discussions are just guys repeating stuff they have heard with zero real idea what they are talking about.
while theres generally some relation of port cross sectional area to the listed port CCs its NOT a direct linear relationship, and its the cross sectional area,shape, length and surface finish not the port CCs that matter to the air flow., and if the exhaust system can,t effectively scavenge the cylinders or the intake can,t supply the flow, or the cam duration and lift don,t match the intended port flow rates performance will suffer

While theres no direct linear relationship between port flow and hp there is a strong relationship.So you'll generally want the highest flow numbers you can get in any port size ranges as a starting point, and yes theres other factors that go into making hp, so combustion chamber design,compression, cam timing, cylinder scavenging ETC. will effect results.you might want to keep in mind that carbs are flow rated at 1.5 inches of mercury, heads at 28" of water and that anyone who has ever watched a vacuum gauge, will tell you the readings fluctuate rapidly, under most conditions and vacuum tends to vary with the cam,used the rpms the engines running, displacement and intake design,exhaust scavenging,ETC.
in most cases there factors are at least, mostly or on occasion, partly understood well enough that theres formulas and charts that can be used to define probable results, that parts selection will result in to a reasonable degree.


you don,t build an engine combo by selecting just heads, first and then matching the other components to that head flow rates, you select a hp/torque/rpm power band as a goal and then select the necessary components to slightly exceed that hp/torque/rpm power bands requirements knowing all parts NEVER work at 100% of the potential when matched in a combo.
the ballpark formula is
.257 x port flow x 8 = potential hp

EXAMPLE
if your intake port flows 250cfm
.257 x 250 x 8 = yields APPROXIMATELY a 514hp figure before your heads become the limiting factor

this ballpark formula is based on average results FROM WELL TUNED HOT ROD TYPE Engine's USING DYNO FLYWHEEL RESULTS
NOT true race only engines or street engines
also keep in mind that the results you'll get will differ and to get those numbers it requires the engine to operate in its best rpm range with a cam and compression levels that match and all other components must also match
if your heads flow 279 cfm at .700 lift but your intake only flows 240cfm and your cam has a max lift of .550 your not going to get the max potential HP results
for the ball park formula to work you must have a tuned exhaust, a cam that matches the compression ratio and all other parts must flow at least close to as well as the heads at the max figures
also keep in mind that the ports cross sectional area should keep the airflow in those ports in approximately the 200fps-300fps ranges
airflow speeds that very greatly from that 200fps-300fps will not tend to give best results, thats why huge ports that flow exceptionally well don,t work well on smaller displacement engines
port lenth also has a large effect on the rpm range that the ports can effectively pack the cylinders at due to harmonics in the column of air
PORT SIZE FLOW AND THE RELATION TO CAM DURATION, and your displacement and the tuned rpm that your headers operate best in for scavageing the cylinders also comes into play here!


FIRST, This will not be anything more that a brief glimpse into a subject that takes years to understand and I’m sure there are a few people on the site that can give more exact info! This is meant to apply to the 350-383 sbc engines most of us are using
My purpose is merely to give an idea as to the relationship between the factors and yes IM ignoring several minor factors to make things easier to understand
But lets look a a few concepts

(1) There are 720 degrees in a 4 cycle engines repetitive cycle of which between about 200degrees to about 250 degrees actually allow air to pass into the cylinder, (the valves open far enough to flow meaningful air flow) and the piston has a maximum ability to draw air into that cylinder based mostly on the engines displacement and the inertia of column of air in both the intake port and the suction (or negative pressure the PROPERLY designed headers provide) this produced a max air flow thru the ports, the greater the volume of fuel/air mix effectively burn per power stroke the greater the engines potential torque production, the faster you spin an engine the greater the NUMBER OF POWER STROKES PER MINUTE, and up to the point where the cylinder filling effectiveness starts falling off due to not enough time available to fill that cylinder the torque increases, above that rpm or peak torque it’s a race between more power stokes and lower power per stroke

As air enters an engine it normally travels thru both an intake system and the cylinder heads intake port to eventually pass into the cylinder thru the valve. The valves in a normal small block corvette engine are between 1.94 and 2.08 in diameter, that’s between 2.9sq inches and 3.4 sq inches of area, but because the valves require a seat that at a minimum are about 85%-90% of that flow area we find that the intake port even with out any valve has a max flow of not more than about 90% of the flow thru a port of valve size. Or in this case 2.46 sq inches-2.9 sq inches of port area, Since you gain little if any flow having a port that’s substantially larger than the valves AT NORMAL ATMOSPHERIC pressures and since you can’t substantially increase the valve sizes for several mechanical reasons you must improve efficiency, this is done in two major ways, you can match the intake port length and cross sectional area to the engines most efficient rpm range on the intake side, to build a positive pressure behind the intake valve as it opens and match the exhaust length and diameter on the exhaust side to provide a negative pressure to help draw in more volume this will require the cam timing match that same rpm range of course. By experimentation its been found that air flow port speeds in the 200-320 cubic feet per minute range are about the best for a chevy V-8 now lets say you have a 383. 383/8=47.875 cubic inches per cylinder, the rpm range most used is 1500rpm-6000rpm so that’s where are cam and port size must match, you can do the math , (47.875 x ½ engine rpms = cubic inches, divided by your cams effective flow duration, (use 210-235) as a default for a stock cam) x 720 degrees/1728 (the number of cubic inches in a cubic foot) to get the theoretical max port flow required (I will save you the trouble its 250cfm-275cfm at max rpms and about 2.4-2.9 sq inches of port cross section, depending on where you want the torque peak, or use this handy calculator,

Intake Runner Area = Cylinder Volume X Peak Torque RPM 88200
Or this helpful info in this thread

very important calculator info

viewtopic.php?f=52&t=322

viewtopic.php?f=44&t=10910

Either way you’ll find that you’ll want a port size in the 2.4sq –2.9 sq inch area
Now use this calculator to figure ideal port length, REMEMBER youll need to add the 6” in the cylinder head to the intake runner length to get the total length and you can,t exceed the engines REDLINE RPM which with hydrolic lifters seldom is higher than 6400rpm

http://www.bgsoflex.com/intakeln.html


Ever wonder why your engines torque curve gets higher with the engines rpm level until about 4000rpm-5500rpm(DEPENDING ON YOUR COMBO) but fades above that rpm level?
well it depends on several factors, first as long as the cylinders can fill completely you get a good fuel/air burn so you get a good cylinder pressure curve against the piston each time the cylinder fires, THE ENGINES TORQUE CURVE INCREASES WITH THE NUMBER OF EFFECTIVE POWER STROKES PER SECOND, at very low speeds there’s not enough air velocity to mix the fuel correctly or produce a effective ram tuning effect but as the rpms increase the cylinders fill very efficiently until the rpms reach a point where the cylinders just don’t have the time necessary to flow
enough air through the valves to fill the cylinders , remember a 5000rpm the intake valve out of 720 degs. in each cycle opens for about 250degs of effective flow even with a hot roller cam, now that’s only about 35% of the time and there’s 41.6 intake strokes per second , that’s only 1/60th of a second for air to flow into the cylinder
Its your engines ability to fill the cylinders that increases your power and the more efficiently you do that the higher the rpm level you can accomplish that at the more power your engine makes, remember the formula for hp is (torque x rpm/ 5252=hp) so moving the torque curve higher in the rpm range increases hp but at some point the time available to fill the cylinders becomes so short that efficiency begins to drop off rapidly, the peak of efficiency is reached normally in the 4500rpm-5500rpm range, and as rpms increase its a race between more power strokes per minute trying to raise the power and the increasingly less effective percentage of cylinder filling dropping the power.
Volumetric Efficiency
The volumetric efficiency of a 4-stroke engine is the relationship between the quantity of intake air and the piston displacement. In other words, volumetric efficiency is the ratio between the charge that actually enters the cylinder and the amount that could enter under ideal conditions. Piston displacement is used since it is difficult to measure the amount of charge that would enter the cylinder under ideal conditions. An engine would have 100% volumetric efficiency if, at atmospheric pressure and normal temperature, an amount of air exactly equal to piston displacement could be drawn into the cylinder. This is not possible, except by supercharging, because the passages through which the air must flow offer a resistance, the force pushing the air into the cylinder is only atmospheric, and the air absorbs heat during the process. so, volumetric efficiency is determined by measuring (with an orifice or venturi type meter) the amount of air taken in by the engine, converting the amount to volume, and comparing this volume to the piston displacement.
this increases until the torque peak then falls as the rpms increase. Here is a rough guide to match duration to port flow at different rpm level
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if you’ve been following along you’ll find that you’ll need intake ports about 2.3-2.9” sq inches in cross section, and between 12” and 21 “ long (DEPENDS ON WHERE THE ENGINE IS DESIGNED TO MAKE MAX HP) and cam timing in the [email]215@.050[/email] to [email]-240@.050[/email] lift range, as the rpms or displacement increase either the port flow or the cams duration must increase or the engines cylinder fill efficiency rpm will drop!
Now this is important, as the port flow efficiency goes up though the use of longer and larger intake ports the cam duration could remain the same or even be lower and you get more efficient cylinder filling as the rpms increase, that’s why high efficiency port designs like on the LS1 can use lower duration cams to flow similar total air flow thru the ports than the lower efficiency ports like the old fuelie heads could but at some point all ports reach max flow and an increase in the time the valves remain open at higher rpms increases the cylinder fill efficiency and that increases the engines ability to make torque at that rpm range


you might want to watch this video

http://www.youtube.com/watch?v=N_ART4SBmdg

the basic rule is a dual plane intake will almost always be the better choice over a single plane intake if the cam duration is under about 235 degrees@.050 lift

Ive built 383,396,421 and 427 SBC combos and used both the 195cc and 210cc AFR, brodix 180,200cc , trickflow, 195, 215 and dart 200cc,-230cc heads,and Ive used the 750cfm and 850cfm carbs.

ok theres very little gained with swap between the 750/850 cfm carbs in either direction, both are almost interchangeable with the correct tuning in my opinion, but ID prefer the 750cfm about 90% of the time, as its slightly crisper in the throttle response and Id doubt youll give up 3 hp at peak with the small rated carb

the 195cc class heads produce slightly more low rpm torque, the 210-230cc slightly more peak hp,in a combo thats set up correctly to take full advantage of either heads characteristics, again the difference is more in the intake, cam, compression and exhaust tuning, but given a choice id select the 210cc heads about 75% of the time if the peak hp was the goal and the 195cc on a car used mostly on the street, as a general rule if I use a single plane intake, and a cam with about 240 plus duration,and 10.2:1 or higher compression, I tend to select the 210-230cc heads, on a dual plane intake , with a cam having under 240 duration,and 10.1:1 or lower compression, Id select the 195-200cc class heads
keep in mind its that total combo with the rear gearing, exhaust and transmission gearing, car weight, tire diam. fuel octane etc. taken into the calculations that matters not a single component

IF YOU HAVE A SET OF REALLY DEEP POCKETS
http://www.speierracingheads.com/SRH2.50.htm
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: sellecting cylinder heads

Postby grumpyvette » November 26th, 2008, 12:04 pm

http://www.alaniztechnologies.com/headterms.html

http://www.airflowresearch.com/articles ... 1/A-P1.htm

http://www.j-performance.com/index.php? ... view&id=28

http://www.chevyhiperformance.com/howto ... index.html

http://www.rbracing-rsr.com/runnertorquecalc.html

http://www.dw1977.cz28.com/photo2.html

http://www.cferacing.com/products.php?id=4

viewtopic.php?f=52&t=2203

http://www.wallaceracing.com/lpv.php

http://www.jonkaaseracingengines.com/products.html

http://www.profilerperformance.com/bbc-heads-174.html

http://www.totalengineairflow.com/products/

http://www.rbracing-rsr.com/lovellgascalc.html

http://www.velocity-of-sound.com/veloci ... lator3.htm

http://www.chevyhiperformance.com/techa ... _database/

http://home.earthlink.net/~hennad/results.html

http://www.malcams.com/legacy/misc/headflow.htm

http://users.erols.com/srweiss/tablehdc.htm

http://www.purplesagetradingpost.com/su ... l#GM%20LT4

https://www.patriot-performance.com/xca ... =76&page=1

http://www.chevyhiperformance.com/techa ... to_11.html

http://www.kendrick-auto.com/head_flow_figures.htm


theres a good deal of info on assembling a 383 -406 sbc in this thread you might need

viewtopic.php?f=69&t=261&st=0&sk=t&sd=a&start=10


http://www.gofastnews.com/board/technic ... lumes.html

http://www.gofastnews.com/board/technic ... areas.html

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above is a very typical machine shop invoice for reconditioning a set of used vortec heads, notice theres $982 plus in charges and theres a great deal more that could easily be required to recondition used heads, now add the rather typical purchase price of at least $200-$400 for a set of clean used vortec heads and you quickly find you could buy better heads for the cost involved
so be aware that just the cost of used or bare heads is not the total cost youll see.
and THATS NOT EVEN PORTED HEAD OR A 5 ANGLE VALVE JOB OR LARGER RACE VALVES

RELATED INFO
viewtopic.php?f=52&t=8460


up to the rpm range where the port cross sectional area becomes a restriction to flow a smaller port is usually superior
for torque produced, larger ports tend to be less responsive and produce slightly lower torque so you need to match the flow to the displacement and rpm range
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Posts: 14105
Joined: September 14th, 2008, 1:40 pm
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Re: sellecting cylinder heads

Postby grumpyvette » November 26th, 2008, 2:22 pm

read this, BUT keep in mind it does little good to have killer head flow numbers if the intake manifold flows less or if the exhaust is restricting flow, and heads that flow killer numbers at .700 lift, and are designed to feed a 427 displacement at 7500rpm, DON,T do you much good if the CAM you selected has a .520 lift AND ONLY SPIN THE ENGINE TO 6000RPM

http://www.tmossporting.com/tabid/1805/Default.aspx

BTW.
ITS A COMMON MISCONCEPTION,THAT YOU MEASURE PORT CROSS SECTION AT THE PORT ENTRANCE, BUT ITS NOT the port area at the entrance , you need to use in the calculations, ITS the MINIMAL port cross section at the SMALLEST point in the port, usually near the push rod area.
LIKE a funnel, its not the largest part of the opening but the smallest that's the restriction to flow

SO HOW do you MEASURE THEN??

http://www.harborfreight.com/cpi/ctaf/d ... umber=5649

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http://store.summitracing.com/partdetai ... toview=sku
Image

USE THIS

http://www.rbracing-rsr.com/runnertorquecalc.html



http://users.erols.com/srweiss/tablehdc.htm

http://www.malcams.com/legacy/misc/headflow.htm

viewtopic.php?f=52&t=2630&hilit=shrouding

here’s a chart FROM THE BOOK,HOW TO BUILD BIG-INCH CHEVY SMALL BLOCKS with some common cross sectional port sizes
(measured at the smallest part of the ports)
...........................sq inches........port cc
edelbrock performer rpm ....1.43.............170
vortec......................1.66.............170
tfs195......................1.93.............195
afr 180.....................1.93.............180
afr 195.....................1.98.............195
afr 210.....................2.05.............210
dart pro 200................2.06.............200
dart pro 215................2.14.............215
brodix track 1 .............2.30.............221
dart pro 1 230..............2.40.............230
edelbrock 23 high port .....2.53.............238
edelbrock 18 deg............2.71.............266
tfs 18 deg..................2.80.............250

Potential HP based on Airflow (Hot Rod, Jun '99, p74):
Airflow at 28" of water x 0.257 x number of cylinders = potential HP
or required airflow based on HP:
HP / 0.257 / cylinders = required airflow

a good deal of the results you see on the EXHAUST side AND THE INTAKE SIDE are greatly effected by the scavenging design rpm range of the headers and the restriction to flow beyond the collectors.
YOU CAN,T CRAM MORE IN TILL THE OLD F/A CHARGE VOLUME IS REMOVED, and with a properly designed low restriction exhaust , the fast moving exhaust mass in the headers helps to drag in the next intake charge into the cylinders.
generally you can get a bit of useful info with a pressure gauge, if the exhaust have greater than about 1 PSI you've generally got a restriction that's hurting the power,and that restriction to flow DOES effect the engine tuning results and the cam timing you'll want to use.
now Ive generally found that the collector lengths on commercial headers are too short and in many cases designed wrong to maximize the cylinder scavenging.
it does little good to stick a decent set of headers on a car and then hook the collectors up to a restrictive 2" or 2.5" exhaust either.
if your car runs noticeably better with open headers at the track, you can bet your street exhaust is restrictive.

there ARE aftermarket header merge collectors and things you can do to reduce the restriction to flow, (THE (H) and (X) pipes that split or share the exhaust between both sides, and a custom 3" exhaust and low restriction mufflers comes instantly too mind here)
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Posts: 14105
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Re: sellecting cylinder heads

Postby grumpyvette » December 2nd, 2008, 8:59 pm

keep in mind swapping heads gives you the option to increase or decrease the compression ratio of the combo, and once the compression ratios increased you can use a longer duration cam timing without sacraficeing a great deal of low rpm torque, that you would loose with the lower compression ratio if the same cam were installed in the lower cpr combo

"(assume on a stock 350 small block)

Speaking in generalities and assuming no other changes, what's the relation between cylinder head combustion chamber size and overall engine compression?

Does just changing heads from a stock 76cc head, to a head with a smaller chamber make that much overall difference on engine c/ratio? Such as a 64cc or 58cc chamber. How about changes on necessary octane requirement?

Just curious to see what can be expected. I've read plenty on what performance gains can be had and what would work best for 350 TPI, but curious to see the other factors may play out.

Thanks"

Ok lets look at it a bit, theres two types of compression ratio, static and dynamic, keep in mind its MOSTLY dynamic compression ratio, that effects your results.
youll gain about 3% in hp increasing the effective static compression ratio one full point, so swapping from a 9:1 to a 10:1 cpr boost torque about 3%
swapping from a 76cc head to a 58cc head is a 1.84:1 cpr change so you can reasonably expect a 1.84 x 3% or a 5.52% boost in torque from that change alone.
if your current engine made 330hp that would jump to about 5.52% higher if the tq curve remained consistant, so youll see about 350 hp.


one of the the main functions of compression is to pack the fuel/air mix into a tight area for both fast effective ignition and to provide a mechanical advantage for the piston & rod assembly to push against the crank throw,as that mass in the combustion chamber burns and rapidly expands.

lets look ast your question, given identical 350 displacement engines with flat top pistons and a comon .032 thick head gasket, a .023 deck and 5cc valve notches, heres what your going to see in STATIC COMPRESSION,as a result of combustion chamber changes

58cc=10.61/1
60cc=10.36/1
62cc=10.12/1
64cc=9.89/1
68cc=9.47/1
72cc=9.09/1
74cc=8.91/1
76cc=8.75/1

keep in mind you want to stay at about 8:1-8.5:1 in DYNAMIC compression

to run comon pump gas without getting into detonation
that depends on the fuel octane, cylinder head temp. and several other variables but generally 8.0-8.5:1 dynamic works out well if your going to run mid grade pump gas

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calculators


http://kb-silvolite.com/calc.php?action=comp

http://www.csgnetwork.com/compcalc.html

http://www.bgsoflex.com/cr.html

http://www.velocity-of-sound.com/veloci ... lator3.htm

http://www.rbracing-rsr.com/runnertorquecalc.html

http://www.rbracing-rsr.com/lovellgascalc.html

threads/info

http://www.circletrack.com/enginetech/c ... index.html

http://victorylibrary.com/mopar/chamber-tech-c.htm

http://victorylibrary.com/mopar/piston_position-c.htm

http://victorylibrary.com/mopar/cam-tech-c.htm

http://www.corvettefever.com/techarticl ... index.html

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=727

http://forum.grumpysperformance.com/viewtopic.php?f=50&t=499

http://www.eurospares.com/graphics/engi ... 0Time!.pdf
Porting School #5 Identifying Primary Restrictions


#5 Port Appraisal
The first step toward more flow is identifying a flow restriction.
By

David Vizard

The small block Chevy head with it’s pushrod pinch point just in from the manifold face probably brings about more initial porting misconceptions than any other head. A novice looking at such a head almost immediately assumes that the pinch point must be the restriction stopping the engine from making much bigger hp numbers. The reality is far different and it sometimes takes a graphic example to convince a would-be porter otherwise.

Granted there are a lot of aspects than we need to cover if the intent is to develop an optimal port for what ever performance application you have in mind. And before any of you over enthusiastic novice porters start bombarding me with questions on what will be down the road topics let me tell you - we will get there. But we have to start somewhere so let us begin by considering the magnitude of the task at hand – namely filling cylinders with an air fuel mixture up to high rpm. The following drawing should put things into prospective. When you realize the physical proportions of the elements involved achieving our goals don’t look to be quite as easy to achieve.



The real point to note here is how small the intake valves are in relation to the volume of air that has to be drawn in to make just 400 hp. That is a figure that most of us relate to nothing more than a hot street 350. If the goal is 600 hp the task of filling the cylinders is even more daunting. As much as this looks to be a great illustration of the situation involved it does in reality fall short. Let us not forget that at any one moment in time in a V8 that 5 of the 8 valves are closed so in effect all the air has to pass through just 3 valves. Things are now looking really serious but it does not stop there. We also must take into account that valves open and close and that on average they are at half lift. If we now add this into the equation we can say that for all practical purposes all that air for 400 hp has to pass through the equivalent of just one and a half of the valves shown. So what does this all tell us? What it means is if you want to make real hp from your engine you had best be a real porter and know what you are doing – because it is hardly all a walk in the park!


If you have now absorbed the implications of the above then it’s time to move an and establish just where in the induction/exhaust system the real restrictions lie. In an effort to put some numbers on it I did, many years ago, saw up a small block Chevy head and flow each individual section to get a better idea of the relative flow efficiencies of various parts of a port. Although I am using a small block Chevy port here as an example what we are looking at carries over to most ports. First let’s look at a typical production casting as per that shown below.


This head has the valve at about what would be half lift for a sane performance street cam. This represents the average lift seen at the valve.



Using a clay radius entry on each section (not shown in these drawings) the flow figures are seen. From these numbers it is obvious that the entry point A is not the prime restriction but the area at and around the valve seat.


From the above drawings it appears that the point of greatest flow restriction is at the valve seat. This is actually the case and applies to both the intake and exhaust. The reality of the situation is that the most important and influential part of any cylinder head port is the part ½ inch above to ½ inch below the seat itself. From this we can see that any work we do to the head should start by shaping the before and after seat area such that it flows as effectively as possible.

For the novice head porter the info just given could well save a lot of wasted time. Before even considering enlarging the pinch point area of the port (or any part of the main section of the port on any head for that matter) you should come to terms with the seat and bowl area. Reworking this is often termed ‘pocket porting’ but it can mean different things to different folk. Here, for every-ones benefit, is the GFN definition of pocket porting. It essentially implies the blending of the valve seat into the bowl area in a smooth and well rounded manner. In our case it also means tidying up the short side radius of the port so as to make the best of that. If you are doing a pocket port job then it also implies that the intake and exhaust valves have a blending form applied to them on the back face, and in the case of the exhaust, a radius on the front face. This plus a little chamber work pretty much constitutes a pocket port job. As to how effective it can be we have to consider what it was we started with. If it was a stock Ford or Chevy head prior to about 1990 the improvements can be quite substantial. In fact a pocket porting job well done can find about 2/3 of the extra air available from a basic full porting job but for about 1/3 of the expenditure in time and effort. This makes a pocket porting exercise a very effort effective deal. For later style heads such as the Chevy Vortec heads there is less to be gained from the intake although the exhaust responds well. These later heads are manufactured using a far more refined casting technique and, as a result, the factory leaves less on the table for the porter to find.

In Porting School #6 we will continue our journey through the inlet flow processs in more detail and reveal some little known methods of identifying and minimizeing valve shrouding.



David Vizard
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Re: sellecting cylinder heads

Postby grumpyvette » December 12th, 2008, 1:08 pm

ITs rather foolish to start with stock cast iron cylinder heads if your goals are over about 400hp with a sbc, use something like the 882 heads that are serviceable and with minor port work you'll get to that level of hp,but even the vortecs flow better, and might be a better choice ,if your looking for basic cheap transportation those heads work, but a great deal of an engines potential power lies in selecting the correct cylinder heads, if your thinking of building well over 400 hp Id surely look elsewhere, if your looking to exceed 400hp ID suggest the cheaper (yeah still expensive, but much better)aftermarket heads, that flow better. if your looking for a lot more your almost certainly going to need extensive and expensive port work or aftermarket cylinder heads.

mid range options
http://www.jegs.com/p/Dart/756811/10002/-1

http://www.jegs.com/p/Edelbrock/758343/10002/-1

http://www.jegs.com/p/Brodix/760699/10002/-1

http://store.summitracing.com/partdetai ... toview=sku


better for peak HP
, but the matching components get expensive fast

http://store.summitracing.com/partdetai ... toview=sku

http://store.summitracing.com/partdetai ... toview=sku

http://store.summitracing.com/partdetai ... toview=sku
port size to displacement guide
Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
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Re: sellecting cylinder heads

Postby grumpyvette » December 13th, 2008, 6:33 pm

what tends to make me crazy is guys that insist on running vortec or similar small port heads and a dual plane intake for max low rpm torque, when I or someone else builds thier engine, BUT ,who then come back and want thier 383-421 sbc to run the big hp/tq numbers and pull hard at 6000rpm and above where those small ports are far past there effective air flow limits
Ive built some KILLER engines useing the 215cc and 230cc IRON EAGLE heads, TRICKFLOWS,BRODIX,AFR and SIMILAR larger port heads that made great torque in the low and mid ranges, a dual plane intake,with long runners and a 600cfm-750cfm carb helps, as does a cam thats designed for the midrange torque, and full length headers , with 1 5/8" primairies,its NOT the port size in the cylinder heads ALONE that determines the results! its the COMPLETE MATCHED COMBO and the thought that was put into makeing the components match the intended power curve, and matching the cars rear gear and stall speed to that power curve, sure you might be running slightly higher average rpms, to get the best power ,but youll be making a whole lot more power at the rear wheels too!
if you want to get good mileage and decent torque and limit yourself to 1500rpm-3500rpm the small port vortec type heads work great on a 350,thats what G.M. spent the money researching the design to do! ,they are after all TRUCK HEADS!
but increase the displacement to 383 or more and spin the engine to 6500rpm and they become a huge restriction!
while a larger head can give up very little if anything down low in the rpm range but pull far bigger numbers on the hp/tq up higher in the rpm range simply because its still able to flow the necessary voluum of air the engine needs, G.M. knows that! but they also know that 90% plus of the time EMISSIONS and GAS MILEAGE and smooth just off idle low rpm torque is where most engines are used, so they build to fit MOST users expectations

http://www.rbracing-rsr.com/runnertorquecalc.html

play with the calculator(above) youll soon see the vortec heads are designed for max tq at 3000rpm,and it takes a significantly larger head to make good power in the 5800--6400rpm range where a good race engine needs to operate
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
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Re: sellecting cylinder heads

Postby grumpyvette » December 22nd, 2008, 11:02 am

http://www.dw1977.cz28.com/photo2.html

http://boosted.envy.nu/articles/porting1.htm

http://www.chevyhiperformance.com/techarticles/95518/

http://www.edelbrock.com/automotive/head_flowdata.html

http://chevyhiperformance.com/techarticles/41598/

http://www.kendrick-auto.com/head_flow_figures.htm

http://www.malcams.com/legacy/misc/headflow.htm

http://www.topher.net/~bearman/gmheadcomp.html

http://purplesagetradingpost.com/sumner/techinfo/heads1.html

http://www.geocities.com/z28esser/headcomp.html

this might help


1) open throat to 85%-90% of valve size
(2)cut a 4 angle seat with 45 degree angle .065-.075 wide where the valve seats and about .100 at 60 degrees below and a .030 wide 30 degree cut above and a 20 degree cut above that rolled and blended into the combustion chamber
(3)blend the spark plug boss slightly and lay back the combustion chamber walls near the valves
(4)narrow but dont shorten the valve guide
(5) open and straiten and blend the upper two port corner edges along the port roof
(6) gasket match to/with intake and raise the port roof slightly
(7) back cut valves at 30 degrees
(8) polish valve face and round outer edges slightly
(9)polish combustion chamber surface and blend edges slightly
(10) remove and smooth away all casting flash , keep the floor of the port slightly rough but the roof and walls smoothed but not polished.
(11) use a head gasket to see the max you can open the combustion chamber walls
(12) blend but don,t grind away the short side radias


http://www.ws6transam.org/ported.html

http://www.sa-motorsports.com/diyport.shtm

http://www.eecis.udel.edu/~davis/z28/buildup/plenum/

http://www.babcox.com/editorial/us/us110128.htm

http://www.diyporting.com/Shrouding.html

http://www.babcox.com/editorial/ar/eb120121.htm
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
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Re: sellecting cylinder heads

Postby grumpyvette » January 15th, 2009, 7:27 pm

hey grumpy... Aluminum:a weak metal with an over exaggerate reputation.i.e:(aluminum cylinder-heads)
example of over exaggerated reputation: Aluminum cylinder heads are better.


your welcome to your OPINION, and free to run what you wish,but ID bet that opinion changes the first time you crack chunks off your cast iron cylinder heads, that you've got $1200 in port work done too and they get thrown in a dumpster as non-repairable, and yes all heads that are installed on a race engine will eventually get worn or damaged.
a decent set of aluminum heads has several BIG advantages over cast iron, provided you use the correct coolant so corrosions not a problem.
first like you stated
(1)they are significantly lighter in weight
(2) they are far easier to repair if damaged
(3) they are far easier to weld, if they require modifications that require adding a bit of material.
(4) they are easier to PORT or do machine work on.
(5) they tend to transfer heat to the coolant far more efficiently
(6) given equal compression ratios theres a slightly lower tendency to get into detonation

[color=004040]Cast iron:A metal with a sleeper touch.a stronger,more efficient metal.i.e(cast iron cylinder-heads).cast iron cylinder-heads have been used on every thing from the first engines all the way up to high horsepower engines of today.

look no matter what you say,aluminum heads are crap.sorry,thats facts.if not,then why when,cars and truck started being equiped with these kinds of heads from the factory,did the compression ration jump up and the same engine with cast iron heads make 15hp more?[/color]


cast iron castings hold heat and transfers heat to the coolant noticeably slower, making cast iron heads more prone to detonation at any given compression ratio, the same reason aluminum heads can generally be used at a slightly higher compression ratio, and BTW, if both materials are run on very similar engines theres rarely a noticeable difference in hp, especially if the compression ratio on the aluminum head configuration is boosted in compression just a bit , or has a thermal coating in the combustion chamber to slow the heat loss rates,to run at equal pressure and heat levels
there are more drawbacks about going to aluminum heads then i would care to deal with.the only positive thing is,yes they take weight off the front.
BE AWARE, that theres a significant variation in spark plug location between different cylinder head designs,made by different manufacturers ,and theres both strait and angle plug heads and even the angle plug heads vary a good deal between designs, and many headers won,t work with a few cylinder heads in some applications so its almost mandatory that you call and talk too the tech support guys from both the cylinder head and headers manufacturers, to ask if any specific combo has a history of clearance issues BEFORE purchasing your headers or cylinder heads or both.
[/quote]


reading material



http://www.hotrod.com/techarticles/alum ... index.html

http://www.chevyhiperformance.com/techa ... index.html

http://indyheads.com/images/price2012.34.pdf

http://www.carcraft.com/techarticles/cc ... index.html

http://www.carcraft.com/techarticles/cc ... sults.html

http://www.chevyhiperformance.com/techa ... index.html

http://www.circletrack.com/enginetech/c ... index.html

the material the heads are manufactured from will have a big effect on their ability to dissipate heat quickly from the combustion chamber,increasing compression tends to increase the heat generated during combustion, aluminum transfers heat much faster than iron into the coolant, and its that factor more than most that forces you to reduce the effective compression slightly compared to an aluminum head IF your getting into the detonation range due to heat, of combustion, compression,and the ignition advance
the surface finish and shape of the combustion chamber and piston dome,coolant temp. air temp,the combustion chambers tumble and swirl, the fuel octane, the quench/squish distance, spark plug heat range, also will effect your engines tendency to reach detonation
as a general rule on pump gas the temp in the combustion chamber is the limiting factor on reaching detonation.

http://www.chevytalk.org/fusionbb/showtopic.php?tid/92966/
Image

short answer, aluminum tends to allow you to run about 1/2 point more effective compression, IE, if iron heads get into detonation at 10:1 ALUMINUM might ALLOW YOU TO RUN 10.3-10.4:1 BEFORE GETTING INTO DETONATION, BUT ON THE PLUS SIDE AT LEAST IN THEORY IRON HEADS AT ANY GIVEN CPR WILL HAVE A SLIGHT ADVANTAGE IN HP
but in my real world testing the difference is much closer almost non-existent
the main advantage I see in aluminum heads is lighter weight and their much easier to repair when damaged

you DON,T WANT TO GET INTO DETONATION

http://www.sdsefi.com/meltdown.htm
Image

http://www.popularhotrodding.com/tech/0 ... index.html

http://www.misterfixit.com/deton.htm

http://www.kennedysdynotune.com/Dynamic%20Compression%20Tech.htm

http://www.misterfixit.com/deton.htm

http://www.kb-silvolite.com/article.php?action=read&A_id=36
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: sellecting cylinder heads

Postby grumpyvette » January 17th, 2009, 4:13 pm

http://www.chevyhiperformance.com/techa ... index.html

http://www.competitionproducts.com/prod ... CH353-ES-1

http://www.chevyhiperformance.com/techa ... index.html

http://www.crateenginedepot.com/store/B ... 857C0.aspx

http://www.sdpc2000.com/product/2553437 ... rHead.aspx



read thru this, its basically an engine build where they use all the tricks to get a fairly stock set of mildly reworked large port vortec heads , with a much improved valve train to produce thier max power

now those heads, intake and a milder roller cam, would be more useful to most of us ,on a slightly less exotic 406 or 383 SBC combo

Vortec Bow-Tie Brief
There are two versions of the new GM Performance Parts Vortec Bow-Tie cylinder heads: This one, PN 25534371 (bare) and PN 25534431 (complete), with the larger ports, and another with smaller ports, PN 25534351 (bare) and PN 25534421 (complete) with 185 and 65cc volume, otherwise, the architecture and improvements over the L31 design are the same. We will test the smaller version very soon in a dynamometer exercise. We were able to get an exclusive look at the big-port heads just as they were used in a NASCAR-type application.

Out of the box, they feature revised intake and exhaust ports and are machined for a 2-inch intake and 1.55-inch exhaust valves. The deck surface is 0.045-inch thicker than the L31s, and it has 65cc combustion chambers, a 206cc intake, and 77cc exhaust ports (see Flow Chart). The head is also machined for 3/8-inch screw-in rocker studs and a large valvespring pocket, and it will accept up to a 0.530-inch lift camshaft without modification. These castings are identified by the Bow-Tie logo below the exhaust port and the Vortec logo on top of the intake port area. The GM logo is also cast into the bottom of the intake port runners.

All concerned will be delighted to hear that the head includes intake manifold mounting holes for both early-model six-bolt and late-model four-bolt Vortec design. Mandated GM intake manifolds include a raised runner-type PN 10051103 (six-bolt type) or Vortec design PNs 12366573, 12496820, 12496821, 12496822, and 12499371 (four-bolt type). Though production cylinder head and intake manifold gaskets are acceptable, the hot squeal is Fel-Pro (PN 1142 for the MLS and PN 1289 for the intake). As per Scoggin-Dickey, pricing is: small port 4421 complete, $499.95; small port 4351 bare, $269.25; large port 25534431 complete, $539.95; and large port 25534371 bare, $293.25.

http://www.superchevyperformance.com/Vo ... 534431.htm

http://paceperformance.com/index.asp?Pa ... dID=104477


BTW if your looking into aftermarket performance cylinder heads for the BIG BLOCK CHEVY, the blocks have different coolant passage lay outs, and require matched heads and head gaskets , but check with the manufacturer of the cylinder heads, many of the better aftermarket big block heads have been modified with a larger sealing surface areas and relocated coolant passage locations and coolant passage shapes so that they can be used with any and all the generations of the big block blocks, if the correct gaskets are used, simply because the manufacturers found that to be far easier than stocking several different castings for basically similar applications
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: sellecting cylinder heads

Postby grumpyvette » January 26th, 2009, 4:13 pm

http://airflowresearch.com/articles/art ... A11-P1.htm

http://airflowresearch.com/articles/art ... A11-P2.htm

http://airflowresearch.com/articles/art ... A11-P3.htm

http://airflowresearch.com/articles/art ... A11-P4.htm

http://airflowresearch.com/articles/art ... A11-P5.htm

http://airflowresearch.com/articles/art ... A11-P6.htm

http://airflowresearch.com/articles/art ... A11-P7.htm

look this is not a guessing game (selecting the correct port size)you select and verify the correct port size and cross sectional area,using know calculations, valve diam. and flow rate for the application, verify clearances in the valve train,and that the cam and valve train are compatible for the intended rpm band and stress levels,
you match the cams intended rpm and power band to the displacement and compression ratio,make sure the valve curtain are exceeds the port cross section slightly , select the cam lift and duration to maximize the port flow,potential, select headers designed to operate in the same power band, select a drive train that keeps the engine in that power band most of the time.

http://www.rbracing-rsr.com/runnertorquecalc.html

viewtopic.php?f=52&t=322

viewtopic.php?f=56&t=1730

if your thinking about using an older set of fuelie heads, it depends mostly on the condition of the heads,(remember fuelies are on average over 40 plus years old)and on both WHICH fuelie heads they are, and the valve sizes,if they are not 2.02/1.6(if your willing to do minor port, bowl and combustion chamber mods like un-shrouding valves) Id suggest going vortec.

and if your going to have the vortec compatible parts like valve covers, rockers, intake, etc. but in almost every case the VORTEC HEADS will produce slightly better power, unless you do those mods to the fuelie heads

typical reworked fuelie
http://www.kendrick-auto.com/462_chevy_head.htm

vortec
http://www.kendrick-auto.com/vortec_cs_gm_head.htm

keep in mind the average fuelie head has a smaller 155cc port than the typical vortec at about 170cc, and the higher port angle on the vortec heads flows better

http://www.purplesagetradingpost.com/su ... l#GM%20LT4

viewtopic.php?f=52&t=240&hilit=+flow+numbers


http://www.2quicknovas.com/vortecheads.html

http://sallee-chevrolet.com/Cylinder_Heads/Vortec.cfm

Image

BTW theres two common vortec intake manifold gaskets, these vortec heads have taller ports than the standard 23 degree first gen SBC heads
The Fel Pro 1255 is .120 thick
The GM 89017465 is .060 thick
if your restricted to heads that came on most cars then mildly reworked standard 170cc port vortec heads are a decent choice
Image
http://sallee-chevrolet.com/Cylinder_Heads/Vortec.html



VORTEC HEADS YOULL FIND IN SALVAGE YARDS HAVE THESE HEAD MARKINGS
remember this chart?

Image
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
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Re: sellecting cylinder heads

Postby grumpyvette » January 27th, 2009, 12:22 pm

looking to make killer power without ALL the expensive mods like shaft rockers and offset lifters etc, these heads might be what your looking for..

http://store.summitracing.com/partdetai ... toview=sku

http://www.brodix.com/heads/-18x.html

The BRODIX 18X offers the best of both worlds, 18° horsepower without using expensive shaft rockers or offset lifters.
This head offers a dramatic horsepower increase over the 23° cylinder head.
Several advantages of the 18X are intake ports that flow over 320 cfm out of the box, an intake valve size of 2.140, raised intake ports, and shallow combustion chambers. The 18X is an excellent choice for the budget-minded racer who wants to go fast.

sure its expensive, but compared to some of the options its a screaming deal once you total up all the mandatory OTHER parts it takes to correctly run THOSE other heads.....these brodix heads should easily support 600 plus hp on a correctly built, high compression roller cam, 355-427 sbc
just keep in mind a great deal of an engines power potential lies in its head flow, cam timing,displacement and compression ratio, and selecting great heads will usually be money very well spent
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: sellecting cylinder heads

Postby grumpyvette » February 1st, 2009, 6:13 am

Head flow & results on a 383


CHEVY high performance mag for aug 2006 did an interesting comparison between eight different cylinder heads available for $1000 or less.
While youll need to read the article to get all the data, I found it very interesting.
The articles called
“ POWER CURVES”
and it starts on pg 22

Heres a few differant different articles

http://chevyhiperformance.com/techartic ... _0401_imp/

http://chevyhiperformance.com/techarticles/97538/

http://chevyhiperformance.com/techarticles/83858/

http://chevyhiperformance.com/techartic ... 6_thunder/

http://www.chevyhiperformance.com/techa ... ewall.html

the main factors you should notice is that ENGINE DISPLACEMENT MATTER TO THE RESULTS, port size(cc)IE the difference between a 175cc to a 230cc) has far LESS effect on the power curve and peak power that the AIR FLOW, and that flow rates measured at lifts above where the CAM reaches its max lift, and has little to no effect on the power curve, the cams duration and lift and LCA effect the results, the combustion chamber design and valve size DOES matter.
And the intake and exhaust design and flow rates DO EFFECT the power curve.

STANDARD OEM vortec heads have approximately a 170cc port volume and are designed to maximize torque in a 350 at about 4500rpm, they ARE generally slightly better than the older fuelie heads but there are much better heads currently available.
Theres no question that the standard vortec head flows better at near 230cfm than the previous fuelie and corvette heads that flowed less than 210cc in stock form
but theres a dozen or more aftermarket heads that flow well in excess of 250-280cfm, at reasonable valve lift ranges


a couple hours spent reading links could save you a ton of money and work

http://purplesagetradingpost.com/sumner ... eads1.html

http://www.ryanscarpage.50megs.com/combos1.html

http://www.profilerperformance.com/raci ... -23-degree

http://www.jegs.com/i/Edelbrock/350/5089/10002/-1

http://www.racingheadservice.com/Cylind ... minum.aspx

http://www.dartheads.com/products/cylin ... heads.html

http://www.jegs.com/i/Brodix/158/1021001/10002/-1

http://www.summitracing.com/parts/TFS-30400002/

http://www.summitracing.com/parts/EDL-5073/

http://www.summitracing.com/parts/EDL-60719/

you might want to read thru these links, a couple hours reading could save you a good deal of time and money

viewtopic.php?f=52&t=5364

viewtopic.php?f=52&t=5129

viewtopic.php?f=52&t=389

viewtopic.php?f=32&t=5521

viewtopic.php?f=44&t=2099&p=17024&hilit=fuelie+heads#p17024

viewtopic.php?f=52&t=731&p=1539&hilit=machining+vortec#p1539

viewtopic.php?f=52&t=401&p=6078&hilit=machining+vortec#p6078

viewtopic.php?f=44&t=6175&p=19304&hilit=machining+vortec#p19304

viewtopic.php?f=44&t=529&p=657&hilit=machining+vortec#p657

viewtopic.php?f=52&t=266&p=321&hilit=machining+vortec#p321
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: sellecting cylinder heads

Postby grumpyvette » February 1st, 2009, 1:07 pm

this question comes up frequently
"If I were to order a set of heads from summit or who ever and I bought the bare heads rather than a set that were assembled would I have to send them to the machine shop for work or could I buy the valves, springs studs etc and do it myself? "

THE ANSWER DEPENDS ON WHICH HEADS YOU BUY FROM WHICH MANUFACTURER!

Ive seen several sets of bare heads that required HUNDERED$ of dollars in machine work, like doing a 3-5 angle valve job, clearancing the push rod holes,decking the surfaces,combustion chamber mods, spring pockets needed machining , stud pads needed truing and threading for the studs,etc. before valves, springs, rocker studs, push rod guide plates,valve seals ETC. could be installed.
IVE also seen heads that were basically ready for assembly as the came from the box!
ALOT of detailed questions need to be asked before going that route....
BUT ILL also point out that in many cases you'll save a great deal of money, not paying for parts that you won,t be useing and get far better quality components, and be much surer the clearances are correct if you do it yourself with components you select.
you generally won,t get titanium retainers and valves that are .100"-.250" longer and the better quality beehive springs, or similar components and clearance work in an off the shelf cylinder head.
naturally it helps to start with a decent quality casting from a major manufactuer, so components are easily found that match the application.

viewtopic.php?f=52&t=528

viewtopic.php?f=52&t=1005

viewtopic.php?f=52&t=534

viewtopic.php?f=52&t=697

viewtopic.php?f=52&t=553

viewtopic.php?f=52&t=319

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ID suggest you select from heads from these sources

http://www.trickflow.com/egnsearch.asp? ... 4294867081

http://www.brodix.com/heads/heads.html

http://www.dartheads.com/products/cylinder-heads

http://www.airflowresearch.com/

http://www.edelbrock.com/automotive_new ... main.shtml

http://www.indyheads.com/
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: sellecting cylinder heads

Postby grumpyvette » February 17th, 2009, 7:30 pm

FOR those guys thinking they can quickly and cheaply get 500hp from a basically stock 350 sbc........IM going to break the bad news....stock heads are a huge restriction as is basically most of the stock components,to build a 450-500hp small block chevy the block and water pump are usually all thats used in stock condition,
yes IM fully aware, that if you were like most kids growing up in the 1960-1980,s in America, the older kid next door when you were younger threw a 4 barrel intake, headers and a off track Z28 cam in his camaro and it loped like a dragster and was scary fast when you were younger........yeah! it was faster than stock,but probably no where close to the 500hp he bragged about!
IF your looking to keep cost low the lower cost options are between the VORTEC, L98 and older fuelie heads, in many cases, if your given a choice between the l98 aluminum heads of the C4 corvettes heads they are generally moderate to poor performers,compared to vortecs or properly ported fuelies, almost any PROPERLY PORTED set of fuelie heads should out perform the stock or moderately ported l98 heads from what I see., but remember fuelie heads are 40 plus year old technology even the vortec heads usually out perform BOTH in stock form...but if you have port work done to the fuelie heads ID strongly suspect they will out perform the stock L98 heads, but keep in mind the later version aluminum l98 heads weigh less, are easier to repair and allow use of lower octane fuel, so theres other factors to think about


read thru this

http://forum.grumpysperformance.com/viewtopic.php?f=44&t=2099&p=17024&hilit=fuelie#p17024

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=796


ID suggest you start by reading thru these

http://www.amazon.com/Build-Performance ... 714&sr=8-2

http://www.amazon.com/Small-Block-Chevy ... 799&sr=8-7

http://www.amazon.com/Smokey-Yunicks-Po ... 894&sr=8-2


http://www.rustpuppy.org/chp/

http://www.themotorbookstore.com/resmchstvi.html

http://airflowresearch.com/articles/article031/A-P1.htm

viewtopic.php?f=46&t=460

http://www.virtualengine2000.com/

viewtopic.php?f=69&t=780

http://www.chevytalk.org/fusionbb/showt ... id/131229/

http://www.powerperformancenews.com/for ... w-230.html

"swapping from rectangle to oval heads on your big block is a sure way to increase torque"


I saw that posted on a different site and I had to smile, its obvious that that might be true on some applications but its not necessarily even close to valid in all cases,and the individual cylinder heads port design you select, has a bigger effect than similar sized oval vs rectangle port heads, port shape, you can very easily make more total torque, and usually over a wider rpm band with lets say an AFR or BRODIX 300cc-315cc head than a 253-275cc oval port head if your willing to match the rest of the combo to take full advantage of the heads potential. yes its true the smaller heads faster port speeds should produce more efficient volumetric efficiency lower in the rpm band, but that same factor tends to limit the upper rpm potential
your engines torque curve is more the result of displacement, compression,ratio,selected cam timing and both header design (scavenging) and intake design (SINGLE vs DUAL PLANE ETC.)than just port cross sectional area alone, and if your wearing valve guides the valve train geometry and clearances, and lubrication system, and the oil used in it, and your valve spring rates and seals need to be carefully checked and a rocker stud girdle and roller rockers used
and port cross sectional area and flow numbers have a larger effect than port shape alone
naturally you'll need to match the port cross sectional area, length, and plenum to the intended displacement and rpm band, and cam timing, but just assuming a swap from rectangular port to oval will always result in more torque will not always be true over the whole power band, especially if the rest of the combos designed for a totally different rpm band than the heads you've selected.
tweaks like tuned merge collectors, and slightly different cam timing and intake swaps can get a great deal more of the torque potential from a slightly different port size,and there are calculators you can use to find a limited selection of choices,in header length, diam., collector, intake port length and cross section and runner length, plenum size, cam timing and valve size to look thru.. too narrow your search for the best match to your application vs just guessing and swapping parts till you think you've got it correct

http://forum.grumpysperformance.com/viewtopic.php?f=52&t=333
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: sellecting cylinder heads

Postby grumpyvette » June 10th, 2009, 8:05 am

INTERESTING LS head info

http://www.gmhightechperformance.com/te ... index.html

http://www.gmhightechperformance.com/te ... earch.html

http://www.gmhightechperformance.com/te ... /dart.html

http://www.gmhightechperformance.com/te ... brock.html

http://www.gmhightechperformance.com/te ... ports.html

http://www.gmhightechperformance.com/te ... s/tfs.html

ir Flow Research
www.airflowresearch.com Kook's Custom Headers
59 Cleveland Ave.
North Bayshore
NY 11706
Dart Machinery
353 Oliver St.
Troy
MI 48084
www.dartheads.com
Livernois Motorsports
www.livernoismotorsports.com

Edelbrock Corporation Headquarters
2700 California St., Dept. CHP
Torrance
CA 90503

Trick Flow Specialties
1248 Southeast Ave
Tallmadge
OH 44278
www.trickflow.com
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: sellecting cylinder heads

Postby procketus » November 24th, 2009, 12:04 am

Hi Grumpy,
This is related to my post at DC about swapping heads. I had mentioned a friend had a longblock for sale. looked at it today but it is a 305. Pulled the valve cover and the heads are 14014416. Now my question is, with the smaller combustion chamber(58cc I think) and the smaller valves(1.84 int, 1.5exh) would these not perform better? I do remember long ago, about 20 yrs, guys talking about putting these heads on 350 and they ran better. But before I commit to buying these I would like your opinion. If they improve performance great if not I'll pass on them.

Btw, I did replace the bad stud with a replacement screw in type.

Would also like to mention you have a great site here, lot of good info..

Thx,
Steve
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