port speeds and area

[grumpyvette]

I CAN,T EVEN TELL YOU HOW INSANE SOME CONVERSATIONS I HAVE SEEN GUYS GET EVOLVED IN ARE!
GUYS TELL YOU A 210CC air flow research HEADS GOING TO ABSOLUTELY KILL Torque ON A 383 BUT ITS FINE FOR A 400 SBC, WHAT TOTAL b.s, your cylinder heads port size needs to be selected with both displacement and the intended rpm/power band in mind and a 10% change in engine displacement may or may not require a change in port size, as other factors, like the ports minimum cross sectional area and shape, valve curtain area, cam timing,compression ratio, intake runner length and cross section, and your exhaust header design,etc. will have as large or a larger effect results.
look thru the linked info theres calculators , listed in the links and sub-links that can be used to accurately calculate the correct port cross sectional area, and runner length, matching header config cam timing etc.
theres a HUGE MIS -CONCEPTION out there that its always the larger port cross sectional area on any engine that lacks low speed torque, thats responsible for a loss of low speed torque, in most cases it is the combo of a larger than ideal for the application cam duration and a single plane intake, and larger and shorter headers or a restrictive exhaust having been selected ,NOT the cylinder heads port size.
YES cylinder head port cross section will effect the port velocity, but in most cases if your building a performance street cars engine your better off going slightly larger on port size and slightly conservative on the cam duration. and a good dual plane intake and long tube headers with a low restriction exhaust sure helps.


viewtopic.php?f=52&t=8460

viewtopic.php?f=52&t=8460&p=32923&hilit=curtain+flow+angle#p32923

viewtopic.php?f=52&t=322

viewtopic.php?f=52&t=10602

http://www.strokerengine.com/SBCHeadsFlow.html

viewtopic.php?f=69&t=9879

When you see cylinder heads listed as lets say 177cc or 190cc or 210cc port heads thats a reference to the internal intake port runner volume, and while larger port heads tend to flow more air theres no direct linear link, an exceptional 190cc port can out flow a marginal 210cc port, and the shape of the port and its length also effect its volume, a change in port volume of 5% alone with no other change is almost meaningless it the effect it has on engine torque ,compared the intake,runner design, exhaust,or header configuration, compression and cam timing
valve seat and back face angles ,valve diameter and valve lift and duration effect the flow thru the curtain area






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


keep in mind there are tools that can be used to measure air pressure at different points in an intake port that can be used to accurately calculate air flow speeds, and youll moss a ton of info if you don,t read the sub links





on the better 23 degree SMALL BLOCK AFTERMARKET HEADS THERE'S ABOUT 5.5 INCHES OF INTAKE PORT LENGTH ON AVERAGE FROM INTAKE GASKET TO THE BACK OF THE INTAKE VALVE AT THE FAR EDGE






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.circletrack.com/enginetech/1 ... ch_engine/

keep in mind in most cases youll want to select a intake port that will allow the highest air flow rates without getting into port stall or making the port cross sectional area restrict flow.
youll find that the average cylinder head intake gasket is about 10%-15% LARGER IN CROSS SECTIONAL AREA THAT THE NARROW SECTION OF MOST INTAKE PORT EITHER DUE TO THE PORT RESTRICTION NEAR THE PUSH RODS OR VALVE THROATS.
ideally youll want to select a port cross sectional area that will provide near 300fps in air flow rates at or near the intended power peak, which in most performance engines will be close to reaching critical piston durability rpm levels.
on most engines using good performance components thats about 4300fpm in piston speeds.
viewtopic.php?f=53&t=343&p=419&hilit=redline#p419
Calculating the valve curtain area
The following equation mathematically defines the available flow area for any given valve diameter and lift value:
Area = valve diameter x 0.98 x 3.14 x valve lift
Where 3.14 = pi (π)
For a typical 2.02-inch intake valve at .500-inch lift, it calculates as follows:
Area = 2.02 x 0.98 x 3.14 x 0.500 = 3.107 square inches





http://www.circletrack.com/techarticles ... ewall.html
the guys that tell you you should have used 195cc heads on your 383,sbc , and will all point to the larger 210cc head as having lower port flow speeds,...WELL, while thats true, BUT ONLY UP TO A POINT, AND IT MIGHT NOT, BE IN YOUR COMBOS BEST INTEREST TO GO WITH THE SMALLER PORT SIZE the amount of the port flow reduction is all but meaningless, IN MANY APPLICATIONS AT ANY RPM POINT, if you ask them how much the port flow was reduced you'll never get a firm intelligent answer because they don,t have a clue, and are just repeating , like mindless parrots,
repeating crap they heard. DO YOU REALLY THINK SUBTRACTING 4% FROM THE DISPLACEMENT OR ADDING 1% TO THE PORTS CROSS SECTIONAL AREA WILL HURT THE TORQUE NEARLY [b]AS MUCH AS THE ADDED PORT FLOW HELPS THE UPPER RPM POWER CURVE
the difference between those two heads in cross sectional area,is about 1%
the 210cc heads superior,provided your trying to maximize the combos power potential and are running the engine up into its peak potential power band, PORT FLOW SPEEDS WILL BE EQUAL OR HIGHER JUST 200RPM HIGHER IN THE POWER CURVE WITH THAT 383 VS A 400SBC. and your correct the cam, intake and other factors far out weight the difference in port cross section and flow speed differences, any reduction in torque is due to lower compression, a different cam or the intake or header design not the port size difference, and the 210cc head has a marked advantage with the larger cams[/b] JUST REMEMBER THE 210CC HEADS ARE DESIGNED FOR sbc combos WITH CAMS WITH OVER about .550 LIFT AND OVER about 245 DEGS DURATION AT .050 LIFT, AND COMPRESSION RATIOS OVER 10.5:1 IF YOUR LOOKING TO GET THE FULL ADVANTAGE FROM THE PORT DESIGN, AND DISPLACEMENTS OF 377 PLUS.
now obviously if your running a much smaller cam duration,in the 220-230 @50 lift and under .530 lift low 9:1 or lower compression and a restrictive intake, there's not much point in installing killer heads where you'll never get close to the the larger ports full flow potential

many guys will tell you that selecting oval port heads is better on a street car engine, and they generally have a point, yet depending on compression ratio and cam used you may never notice any loss of low rpm torque, if you select a reasonable size rectangular port head and matched components ,this is one of the huge semi-myths about big block engines.
while its true that the low rpm torque does tend to be reduced with stock oval port heads vs stock rectangular port heads ,its also true that the compression, intake manifold, cam timing,rear gearing and header designs all change the results and its very easy to build a rectangular port engine that destroys tires, and theres a huge range in size of the ports in BOTH oval and rectangle port aftermarket heads

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

[color:red]read the article[/color]

Peaks and Averages
................Avg. TQ Avg. HP Peak TQ Peak HP
Iron .. ........541.1 475.0 595 .........521
Edelbrock 582.1 514.9 618 ........582
Dart .......... 584.2 517.7 615 .......595
TFS ................590.3 522.5 626 ... 595
Brodix .....590.8 ........523.0 626 ........597
here read thru these LINKS THERE'S LOTS OF GOOD INFO! and some CALCULATORS YOU CAN USE, and remember the basic concepts apply to both bbc and sbc engines but naturally the port sizes and flow rates and cam timing needs to match the application
a few hours spent reading links can save you a great deal of wasted time, and a great deal of wasted money



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

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

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

http://www.strokerengine.com/SBCHeadsFlow.html

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

viewtopic.php?f=56&t=3155&p=37090&hilit=redline#p37090

viewtopic.php?f=55&t=58&p=36446#p36446

http://www.j-performance.com/index.php? ... view&id=48

A VERY USEFUL set of CALCULATORs
http://www.rbracing-rsr.com/runnertorquecalc.html

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

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

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

viewtopic.php?f=53&t=341&p=30714&hilit=redline#p30714

http://www.s262612653.websitehome.co.uk ... /heads.htm

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

http://www.wallaceracing.com/max-rpm2.php

viewtopic.php?f=52&t=10947&p=48126#p48126

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

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

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

viewtopic.php?f=99&t=6461&p=20464&hilit=head+flow+numbers#p20464

viewtopic.php?f=55&t=1038&p=6713#p6713

http://www.wallaceracing.com/max-rpm2.php

viewtopic.php?f=38&t=1099&p=2152&hilit=volumetric#p2152

viewtopic.php?f=52&t=322

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

viewtopic.php?f=52&t=5364&p=16066&hilit=head+flow+numbers#p16066

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

http://www.jsme.or.jp/esd/COMODIA-Procs ... 4_P535.pdf

http://www.compcams.com/Community/Articles/Details.asp?ID=1737510521

http://www.slowgt.com/Calc2.htm#MinCross

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

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

viewtopic.php?f=50&t=575

http://airflowresearch.com/articles/article115/A-P1.htm

viewtopic.php?f=55&t=624

viewtopic.php?f=52&t=796

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

http://www.chevyasylum.com/chp/

viewtopic.php?f=52&t=1563&p=11966&hilit=head+flow+numbers#p11966

viewtopic.php?f=50&t=1482&p=3509&hilit=volumetric#p3509

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

http://www.carcraft.com/techarticles/11 ... index.html

viewtopic.php?f=52&t=92&p=116#p116

viewtopic.php?f=52&t=2203&p=13143&hilit=head+flow+numbers#p13143

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

http://www.dartheads.com/customer_servi ... .php?qk=34

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

viewtopic.php?f=52&t=90

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

DYNO DON POSTED THIS BIT OF INFO

"AFR 195 Eliminators
actual cc's in the intake port.....184
cross section area...2.13 sq.in
Flow spec's.....281/221

AFR 195 comp Eliminators
actual cc's ....189
cross section...2.15 sq.in
Flow spec's...306/235

Trick Flow 195 K D
before porting actual cc's....185
after porting ...188
cross section....2.13 sq.in
Flow spec's....270/210

Edelbrock Etec 200's
actual cc's before porting N/A
after porting....197
cross section...2.13
Flow spec's...270/218
"



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

your ports cross section selection should depend on the cars gearing , displacement, compression ratio,and average rpm range and the cam timing you'll be using, a 12:1 cpr 383 with a .650 lift cam that spends most of its time in the 4500rpm-7500rpm band will take a larger port cross section , than a 9:1 cpr 383 with a .450 lift cam that spends most of its time in the 1500rpm-5500rpm band. or a 350 will work out best with a 180cc port vs a 195cc or even a 200cc port size, ok I understand WHY your thinking that way but Id doubt you've done the math if you still hold that position, here is why, the 195cc port has a cross sectional area of about 2.15 sq inches MAX, the 180 cc ports run close to 2.1 sq inches ,MAX MOST ARE SMALLER IN CROSS SECTIONAL AREA, but think about this, a 2.02" intake valve that's .450" off its seat has a flow curtain of about 2.86sq inches
2.02" diam x pi 3.147 x .450"=2.86sq inches even at that low lift.
the intake runner design and intake plenum and the cam timing, displacement and compression ratio will have far more effect on the port flow than a simple swap from 180cc to 200cc in the head port size

it does absolutely no good to place a cylinder head with with a port cross sectional area [b]thats larger than the intake port that feeds it,beyond the intake runner exit, 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% from entrance to the valve pocket, and the port cross section in the heads a bit smaller than the intake runner.
the port flow is limited by the ports smallest cross section not its largest

http://www.wallaceracing.com/max-rpm2.php

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

viewtopic.php?f=44&t=10910

making even the larger port a restriction, and in any case a difference of about 3%in cross sectional area is in effect meaningless to flow rates [/b]

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

[grumpyvette]

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 calculators, 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
IDEAL FLOW FLUX another critical intake pumping process parameter that has been discovered over the years of ENGINE PRO SOFTWARE DEVELOPMENT is the maximum intake flow per unit of area that can be obtained on the flow bench when tested at 28 inches of H20 .
This value is calculated using the intake throat minimum cross sectional area (CSA) which is usually located just up stream of the intake valve seat insert or seat ring.



the valve seat throat area as a percentage of the intake valve diameter effects the port flow rate, yes the port cross section and angle also effect flow rates and larger valves and larger throat areas with less restriction obviously have some potentially lower flow restriction.
SO HOW do you MEASURE THEN??

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=5649


http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2D900014&N=700+115&autoview=sku



READ THRU THESE LINKS
viewtopic.php?f=52&t=796

viewtopic.php?f=52&t=462

viewtopic.php?f=52&t=322

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=5078

viewtopic.php?f=52&t=8460&p=29682&hilit=head+flow+numbers#p29682

viewtopic.php?f=55&t=624&p=28122&hilit=head+flow+numbers#p28122

viewtopic.php?f=38&t=1099&p=26215&hilit=head+flow+numbers#p26215


runner LENGTH and CROSS SECTION plus PLENUM VOLUME (if there is a plenum)effects the intake harmonics and how effectively you can ram tune the intake runner charge to fill the cylinders, and don,t forget exhaust scavenging , compression ratio and cam timing, and valve curtain area,and drive train gearing must match the intended combos effective operational power band

http://victorylibrary.com/mopar/intake-tech.htm

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

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

http://www.engr.colostate.edu/~allan/fluids/page7/PipeLength/pipe.html

READ THIS ALSO

viewtopic.php?f=3&t=1817&p=4699&hilit=rigged#p4699

I think this may help

http://www.wallaceracing.com/Calculators.htm

http://www.highperformancepontiac.com/t ... index.html

http://www.highperformancepontiac.com/t ... index.html









http://www.superchevy.com/how-to/projec ... ock-build/

Cylinder Head Runner Volume
http://www.racingheadservice.com/rhs/cy ... olume-faq/
Although Racing Head Service® offers many different intake runner volumes in its cylinder heads, chances are that only one or two of them are appropriate for your application. When it comes to deciding which cylinder heads to order, it is important that you make a realistic judgment of your intended use for your vehicle.

Remember that velocity produces low rpm torque, and flow produces high rpm horsepower. So that 170cc cylinder head that you’ve been looking at -with its smaller, higher-velocity runners and valves, is going to accelerate well from a stop, produce lots of low speed torque, and be a great performer below 6000 RPM (which covers about 97% of all street-performance scenarios), but it may not reach the peak RPM you’d want in say, a drag race engine. Conversely, that high–flowing 235cc Small Block Chevy cylinder head that your friends tell you is all the rage at the local track is going to help your engine to rev like crazy and produce a ton of upper rpm horsepower, but it won’t build power below 3500 RPM -making it virtually unusable on the street.

Which is the correct way to go? Most experts will tell you that the answer is not “bigger is better”, but rather that you should run the correct heads for your application with components (cam, intake, exhaust system, etc.) that are designed to work with them. So if you’re looking to build an all-out race car that will never see street duty, that 235cc head with compression, cam, induction, and drivetrain to match will have you winning races in no time. If you just want to get an extra 20 or 30 horsepower out of your street vehicle, and you aren’t planning on performing 4000 RPM launches anytime soon, then that 170cc head is probably the best choice.

The tables listed below will offer some general cubic inch and RPM guidelines to consider when selecting the intake runner volume of your new cylinder heads:

[grumpyvette]

READ THRU THESE, LINKS BELOW AND THE ONES EARLIER IN THE THREAD,theres a great deal of info you can use
viewtopic.php?f=52&t=2077&p=44546&hilit=ccing+heads#p44546

viewtopic.php?f=52&t=2630&p=6788&hilit=+shrouding#p6788

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=528

viewtopic.php?f=52&t=401

viewtopic.php?f=52&t=796

viewtopic.php?f=52&t=148

viewtopic.php?f=52&t=8460

viewtopic.php?f=52&t=975

viewtopic.php?f=52&t=322

viewtopic.php?f=52&t=534

viewtopic.php?f=52&t=389

viewtopic.php?f=52&t=965

viewtopic.php?f=50&t=1266

viewtopic.php?f=71&t=741

[grumpyvette]

ok basics, you can use the calculator links above in this thread to get a better grasp on figures.....

lets look at a typical oval port bbc HEAD,

a valve flows only when its open enought to allow air to pass between the seat and edge of the valve, and since it takes a bit of time for inertia to overcome the movement of the mass thats usually at about .004-.006 lift, on the intakes, exhaust valves are under far more pressure than the 14.7 psi that atmosphere air provides so they can be smaller and still flow well..

Valves open and close much faster tham most guys realize, at only 1000 rpm, the intake valve, opens and closes 8.3 TIMES a second, at 7000 rpm thats 58.3 times a second.

the valve throat area can rately exceed 90% of its dia. and 85% is far more comon.
at some point in its lift the area between the outer valve seat and the lower valve surface or the curtain area that forms a theoretical cylinder wall reaches the same total surface area as the port throat and further flow increases drop off rapidly past that point.
On a 2.2" valve that throat area where the valve seats is probably no larger than about 2" in dia. and has about a 3.15 sq inch area, a 2.2" valve has a perimeter of about 6.9" so a lift of about 0.45" will match the throat flow rates.

obviously you want to reach and exceed that lift point durring the cylinder filling process to maximize the port flow, potential, and hold the valve open at that lift or higher durring peak flow.

max port flow rates are usually reached approximately at or just after the piston passes the 90 degree arc point in its downward rotation.

port angle, cross sectional area, runner length , PLENUM VOLUME, RUNNER ANGLE , CARB VENTURIE SIZE AND LOCATION,and seat and valve design, combustion chamber shrouding, displacement, header scavaging ETC. effect the efficiency of the flow into the cylinder.

TIME, not port size or valve size becomes a significant restriction to flow in a N/A engine at some point

[grumpyvette]

btw, before reading thru this, remember that car weight, rear gear ratio,carb size , cam timing, valve size, header design, converter stall speed transmission gearing and tire diam. all effect the correct choices,
As the head flow rates and cross sectional area get larger in relation to the displacement they feed,the need to use extended duration cams and large plenum areas under the carb tends to get a bit smaller, or lower, at any given rpm level, simply because it takes less time for the port flow to fill the cylinder. but also keep in mind that larger ports are usually designed to run at HIGHER RPMS and use larger matching cam timing to use that extra flow potential, so youll usually be operating the engine at a higher average rpm band which tends to require a matching increase in the cam duration because of the shorter TIME available for that higher flow rate port to flow air/fuel mix into the cylinders.

lets say you have a 11.5:1 compression ratio 540 BIG BLOCK CHEVY
and youve got a choice of some stock but reworked 260cc ported oval port heads that flow 320cfm, at .650 lift and a set of TRICKFLOW 360cc heads, that flow 410cfm,at .750 lift
neither is IDEAL for the application, but EITHER set of heads can be helped a good deal by matching the cam timing and intake sellection and drive train gearing, and either head can produce decent hp/tq..
it should be rather obvious that the smaller heads will require a single plane intake and probably a cam in the 260-270 duration range to maximize the power curve, the larger heads might work better with a slightly lower duration 250-260 duration range and may or may not work best with a dual plane intake to boost port speeds, and cylinder fill efficiency.
but the oval port heads will tend to have a lower torque peak. due to the comparatively restricted flow rates.

were back to use of the calculations, and measuring the port cross section and flow rates, in the linked info above in the thread or here.

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

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

viewtopic.php?f=52&t=322

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

http://www.j-performance.com/index.php? ... view&id=48

heres a good example of fairly large 340cc port head BBC engine potential with a relatively mid range cam, and 10:1 cpr for a BBC of that size

http://www.edelbrock.com/automotive_new ... _675.shtml

[grumpyvette]

interesting article by
mike-cfm


Understanding the benefits of cylinder head porting

Air and fuel equal power. Yes it’s just that simple… or is it? We’ve all heard the adage “an engine is an air pump”. Theoretically; the more air and fuel that pumps through it, the more power it will make. While this is true for the most part, it is a bit more complicated than that. Engines are a nightmare of in-efficiency and parasitic loss; and builders continually strive to reduce these losses. In this article I’m going to lean towards the efficiency side and discuss cylinder head modification to promote power production.
While casting techniques have improved dramatically over the years, it’s still not a perfect process. Core movement and shrinkage are just two of the problems foundry’s face when producing cylinder heads. This leaves room for improvement through porting. So how does porting improve the airflow and power production of a cylinder head? First let’s take a look at what makes one tick. Some of the leading factors in cylinder head efficiency are; size, shape, flow, volume, valve diameter, valve job, and valve angle. I’ll start by discussing size and volume. These may sound like the same thing, but are actually quite different. Size refers to the minimum cross section, or the smallest window in the port defined in square inches (generally found in the pushrod pinch). Volume covers the complete area of the port defined in cubic centimeters. Volume is used to compare similar design heads for the same make of engine, while cross section is used to compare heads of all makes. Engine size, RPM, and power adders directly affect what the cross section and volume of a head needs to be. The shape of the port has one of the largest effects on overall engine acceleration. Sounds odd right? The shape? It’s true; shape promotes velocity, or air speed, through the port. Velocity above all else will make the head most efficient at producing usable power. Valve diameter, throat diameter, valve job, and valve angle are all crucial in allowing air to pass around the valve itself into the cylinder. Last, but not least, flow comes into play. It’s preached the most in all racing circles and flow does have its place, but without shape, cross section, and volume factored in it means little. Like I stated before, velocity is king in making power.

With a basic understanding of the makeup of a cylinder head, let’s move on to the benefits of modifying one. There are many common mistakes and misconceptions about how cylinder heads effect power production. Simply assuming that the biggest, highest flowing head will make the most power can lead to thousands of wasted dollars. I cannot stress enough how important proper port sizing is to optimum power production. Ideal average airspeed through a very efficient port will fall between .45 and .55 Mach, or roughly 550 feet per second on a live, running engine. It takes the correct size and shape of a runner to ensure the engine experiences these average velocities. It is quite possible for a head to gain flow on the test bench, but actually loose velocity and in turn, power. One important thing to remember is that the port not only moves air, but also fuel. Keeping that fuel in suspension is an absolute must to promote power. An experienced head porter will design a port profile based around all needs of the engine; taking into account the drive train, vehicle weight, and its intended usage. With these things considered, and a proper execution of such, the engine should see gains in both power and acceleration. It begins with a precise cut on the valve seats. It’s beneficial to use multiple angles breaking at least every ten degrees, but no more than fifteen on the intake seat. This promotes fuel suspension as a radius cut will allow fuel to fall out and go unburned. A radius cut however, works quite well on the exhaust seat. Moving into the port the throat should be approximately 90% of the valve diameter while the bowl can be opened to 110%. This completes the proper venturi effect around the valve. This is very important as the valve is the biggest restriction in the port. Shaping the guide, using a gentle radius in the corners, and rolling the short turn into the throat will all promote additional flow and air speed.
Now enough of the blah, blah, blah! Let’s move on to a real life example with before and after test results. For this example I’ll talk about a typical 540” Chevrolet with a single Dominator using a 345cc aluminum head. This engine utilizes a .775” lift roller cam and squeezes it with a 13.5:1 compression ratio. It powers a 3200 lbs stock suspension car on 10” tires with a 2 speed automatic transmission. Using the techniques described in this article the heads were modified and improved as shown in the charts below.





Flow Bench Test
Lift Stock Intake / Ported Intake / Stock Exhaust / Ported Exhaust
.200” 138 .........../ 167............. / 110 ................ /118
.300” 213........... / 242............. / 146 ................./ 158
.400” 276........... / 292 ............./ 188 ................./ 202
.500” 328........... / 345............. / 217.................. / 239
.600” 365........... / 382 ............./ 241 ................../ 260
.700” 382........... / 400 ............./ 256................... / 281
.800” 387............ / 415 ............/ 267.................... / 299

Dyno Graph
RPM Before HP / After HP / Before Torque / After Torque
5500 668.7........ 710.3 ............658.2 ..........662.1
5800 722.4 ........ 742.7 ............665.3.......... 671.5
6100 747.0........ 796.7 ............670.4 ..........688.4
6400 778.3........ 822.4............ 672.1.......... 685.0
6700 789.3........ 847.5............ 661.0.......... 676.7
7000 796.6 ........ 862.7............ 652.3........... 655.8
7300 780.2 ........ 871.3............ 636.4.......... 646.4
7600 767.8 ........ 862.7 ............608.1.......... 621.2

On track performance
Before...................... After
9.63 @ 140 mph 9.18 @ 146 mph


As you can see the heads gained in flow, the engine gained in power, and the car went faster. The average measured airspeed increased by 30 feet per second at 28” of water. Translated into live running engine conditions, this calculates to a gain of roughly 65 fps. This gain moved the numbers right into the optimum airspeed range of 0.5 mach. The engine efficiency also improved as show by fuel consumption during the dyno test. The engine made more power using less fuel. The numbers don’t lie. Given proper execution, porting will improve a cylinder heads numbers every time.
__________________
Another quick head article
I didn't have time to go into a lot of detail, I will talk more about the benefits of SB2 heads at a later date.


SB2.2 heads – NASCAR’s gift to the small Chevy

A NASCAR engine is one of the most efficient power plants in all motorsports. Next to the NHRA Pro Stock engine it’s the most technologically advanced domestic V-8. A NASCAR engine makes as much as 2.4 horsepower per cubic inch through a restricted inlet and utilizing a flat tappet cam. These engines must also endure over 500 miles of 9500 rpm torture. The mega-dollar budgets of the teams provide for a slew of well researched parts with top notch development. Just because these parts were designed to go in circles doesn’t mean they can’t be slightly modified to fit a drag racing engine. The SB2 head has seen a few different versions since its inception. I’ll discuss the latest and best version, the SB2.2. This head has had years of testing, re-design, and improvement. All of this testing done with near unlimited budgets and the most advanced equipment possible. As you can imagine… these things are pretty darn good.
Most racers are un-aware, but SB2.2 heads will bolt on a standard Chevrolet block. Yep, no need for an overpriced, custom machined piece. Heck, even a plain old stock 400 block will work. They do require several SB2.2 specific parts, but nothing exotic or beyond the normal needs of any engine. Beyond the head assemblies themselves the SB2.2’s require their own cam, rockers, valve covers, intake manifold, valley tray, pistons, and headers. Any of the parts listed are readily available through various outlets.
Let’s take a look at the specifics of the head. While conventional small block Chevrolets use a 23 degree valve angle, the SB2.2 uses an 11 degree intake valve angle and 8º exhausts. The intake valve is also canted at 4 degrees towards the bore centerline. With these angles the intake valve actually moves away from the cylinder wall during the lift cycle. This allows for a much larger valve as well as a shallower chamber. Port volumes for the SB2 are much larger than traditional small block heads. While a typical aftermarket 23* intake runner may fall in the 215-230cc range, the SB2.2’s often fall between 280-300cc. Now don’t be fooled by these numbers. The intake port may sound huge by comparison, but it is much higher and longer than a factory layout and in turn has a larger volume. When comparing heads of different design for the same engine it is more important to use the minimum cross sectional area, or the smallest area of the port. It’s very difficult to produce adequate cross sections for engines over 400” with 23* heads. Pushrod bulges and low port locations on 23* heads often become a restriction on larger engines. SB2.2’s on the other hand have high ports with offset pushrods and are capable of feeding even the biggest small blocks. The valve layout is a bit different than standard with the outside cylinders intake and exhaust valve positions being reversed. The intake ports are also spread, but not symmetrical. The overall concept of the head design was to optimize the use of a single four barrel manifold by pointing the runners toward the center of the engine. Even with this purposeful design the heads do still lend themselves worthy of a well prepared tunnel ram intake with two carbs. I’ve included a chart for a direct comparison a factory style head to the SB2.2.
The potential of the SB2.2 is overwhelming. With intake flow exceeding 400cfm these heads will support a large amount of power. It is quite common for a 440” engine with two carburetors to make in excess of 1000 horsepower using a well prepped set of SB2.2 heads. Dollars spent can also be quite reasonable when they are purchased in kit form. SB2 experienced shops such as M&M Engines in Indianapolis sell top end kits in various forms starting around $5000. A similar 23* setup would only run about $1000 less. That’s dollar per horsepower value anyway you look at it. Both boost and nitrous friendly as well, SB2.2 engines have been dyno tested at close to 3000 hp. As you can easily see these heads work!

23 degree / SB2.2

IN port volume

200-230cc / 270-310cc

Min. cross section

2-2.3” square / 2.4-3.2” square

Chamber volume

64-76cc / 34-50cc

IN valve size

2.02-2.100” / 2.15-2.2”

Max ave. IN flow

300-330cfm / 400-440cfm

Power potential

650-750 / 900-1050

Kit cost

$6500 / $8200


Kit includes: Complete ported heads (SB2 heads use titanium valves), shaft rockers, sheet metal valve covers, ported intake, custom pistons, rings, roller cam, roller lifters, pushrods, all bolts, all gaskets, valley tray (SB2) header flanges (SB2)
__________________
http://www.cfmperformance.com (317) 627-4186

http://mmcompetitionengines.com/Flow%20Numbers.html

[87vette81big]

Grumpy,
Can you explain how professioal engine builders measure actual airspeeds inside of running engine?
Induction side and intake ports.
Everyone is allways concerned with big airflow cfm numbers.
True it builds big high rpm horsepowet at WOT. But on the street we seldom get to use it most of the time.
I have known a few professioal headporters, been told a cylinder head with a highly efficient intake port has very high velocity. Something you promote likewise. Many cylinder heads as tested on a flow bench will exhibit big cfm airflow but also have bad turbulance present. With a flowbench operating, a loud drumming noise is preset, oscillating up and down in audible frequecy ranges. Clean cylinder head airflow is best I am told , flow bench remains quiet, only the vacuum cleaner motors whirring away.
How come cylinder head manufacturers never promote and publish cylinder head airflow speeds at 12, 28, 45, 65, inches of water vacuum depression? Seems to me it would be much more constructive and usefull when comparing cylinder heads and building an engine for street and stip drag useage.

Brian

[grumpyvette]

http://www.dartheads.com/tech-articles/port-volumes/


Tech Articles
Port Volumes

Posted on June 29th, 2011 under Tech Articles. Both comments and pings are currently closed.

Dart U Master

Port Volumes

By
David Vizard
By David Reher, Reher-Morrison Racing Engines

“The pressure curves explained what I’ve learned about racing engines through years of experience and observation.”

Unless your race car is powered by a jet engine or a turbine, a critical factor in engine performance is the pressure exerted on the pistons. The goal in race engine development is to maximize the cylinder pressure that pushes against the pistons and thereby rotates the crankshaft.

But have you ever thought about how that pressure is applied in the real world?

Several years ago, I had an opportunity to find out what actually happens inside a cylinder. We were working with GM on Pro Stock engine development, and an engineer showed up at our shop with a device to measure cylinder pressure inside a running engine.

As you would expect, a transducer that can survive the heat and strain of a Pro Stock big-block running at 10,000 rpm is a rather sophisticated (and expensive) piece of hardware. We modified a cylinder head to allow a sensor to be inserted into the combustion chamber, where it relayed data on cylinder pressure to a computer. The computer’s software then plotted a curve of cylinder pressure versus crankshaft position. What we saw was very instructive.

I expected that cylinder pressure would rise and fall smoothly as the fuel burned. What the transducer showed was very different: The pressure spiked upward to a sharp peak, and then dropped rapidly. When the fuel-air mixture ignited, the cylinder pressure rose in a nearly vertical line – and then it fell just as quickly. All of this happened within five or six degrees of crankshaft rotation. A big bang . . . and then nothing.

At this point I should point out the important difference between the actual cylinder pressure that we measured and the theoretical Brake Mean Effective Pressure (BMEP). BMEP is a calculation used by engineers and engine builders to compare the relative performance of different engines. It is the average (mean) pressure that would produce the engine’s measured output if the pressure on the pistons was uniform throughout the power stroke – which it obviously is not in the real world.

The engineer also had been testing a small-displacement turbocharged engine, and he shared its pressure graphs with me. The trace was strikingly different from our naturally aspirated engine. In the turbo engine, cylinder pressure rose relatively slowly, maintained a steady plateau for about 30 degrees of crankshaft rotation, and then fell gradually. The peak reading wasn’t as high as our naturally aspirated engine, but the duration was five or six times longer. In effect, the force of the cylinder pressure was pushing against the piston for a much longer interval. It’s no wonder that turbocharged and supercharged engines make so much power!

The pressure curves explained what I’ve learned about racing engines through years of firsthand experience and observation. We worked on a customer’s turbocharged, methanol-burning Toyota engine that produced 2058 horsepower from 189 cubic inches. For those of you keeping score, that’s almost 11 horsepower per cubic inch with a production block and cylinder! We filled the cast-iron block and aluminum head with high-pressure grout, machined billet main caps, and increased the diameter of the head studs to withstand the pressure that this engine was capable of producing.

Induction pressure definitely makes a difference. In a naturally aspirated engine, the force that fills the cylinders is the differential between atmospheric pressure (approximately 14.7 pounds per square inch at sea level) and the lower pressure inside the cylinders. When these pressures equalize, cylinder filling stops. Bolt a turbocharger (or supercharger) onto the engine and now there are three or four atmospheres of pressure in the induction system to fill the cylinders. In the example of the Toyota turbo engine, we had 60 psi pressure to ram air and fuel into the cylinders.

Even with sky-high cylinder pressure, the parts always looked perfect whenever we overhauled that engine. In fact, forced induction engines can be very durable, providing the components are designed to withstand the engine’s output and the fuel/air mixture and the spark timing are correct. The fact that there is always pressure in the cylinder, even during the overlap period when the intake and exhaust valves are open simultaneously, works as a cushion that keeps the piston/pin/rod assembly under constant compression. A normally aspirated engine can be harder on parts because the piston assembly is unloaded during the overlap period, allowing the rods to stretch and varying the loads on the pins and bearings.

I haven’t seen a cylinder pressure curve from a nitrous-injected Pro Mod motor, but I’m certain that the pressure spike is short and vicious. We typically set the spark timing in a nitrous Pro Mod motor at 5 or 6 degrees before Top Dead Center because nitrous oxide is such a powerful oxidizer that the fuel burns extremely fast, reducing the need for more than a few degrees of spark advance.

I’ve seen what the cylinder pressure in a nitrous-injected Pro Mod motor can do, and it’s amazing – flattened wrist pins and connecting rod bores knocked out of round. It takes some serious hardware to stand up to the forces in a Pro Mod engine. We’re not running Top Fuel parts yet, but we’re getting closer.

So whether an engine is competing in Bracket 5, Pro Stock, or Pro Mod, performance is ultimately all about cylinder pressure.

What you need to know to know and why to maximize your cylinder head investment.

Introduction:
We, at Dart, asked engine research consultant, university lecturer and world renowned performance tech author (over 4000 magazine articles and 32 books with #’s 33 and 34 in the making) David Vizard to write up for us the results of his port volume tests. Our goal here is to show that bigger is not always better. A fifty year veteran of high performance engine building and dyno testing plus a 4 figure number of race wins using his go fast technology puts David Vizard in a unique position to do this write up from firsthand experience. My suggestion is take the time to read it and reap the substantial benefits that this knowledge will impart.

- Jack McInnis
Dart Machine Ltd.

More airflow usually equates to greater output but in the case of a cylinder heads port sizing the lure of ‘bigger’ ports can be a trap waiting to snare the uninformed.

A 4 cycle engine is far from being a simple air pump. The principle reason turning apparent simplicity into real world complexity is the dynamic ‘stop – start’ nature of the flow through the engine and the fact that air is very much heavier than is often supposed. Rapidly changing rates of pressure and suction bring strongly into play both the momentum and the pressure wave effects that can be used to boost cylinder filling. At the end of the day this means that for a given displacement and rpm band there is a set of ports that are right for the job. Anything more than a few percent bigger or smaller is not. The following tests will demonstrate the difference delivered by a range of port sizes.

The Test Engine.


The test engine, a 383 Scat cranked stroker, is typical of the majority of small block Chevy’s built these days. Intended for use with 89 octane fuel this engine is well within the budget of most serious hot rodders.

This was one of my budget builds, a replica of which you can get at Pro Stock engine builder/racer Terry Walters in Roanoke VA. () for about $5400 turn key. The final price though will depend on the exact spec. For this test this Scat 3.75 inch stroker (budget cast steel series 9000 crank teamed with Scats budget 6 inch I beam pro-comp rod. Pistons were forged Silvolite ICON items. These in conjunction with the ‘as-cast’ 72 cc combustion chamber Dart heads tested delivered 9.8/1 CR. Had the 64 cc heads been use the CR would have been bumped to 10.7/1 for use with 93 octane. For what it is worth the torque and horsepower jump by about 15 numbers with the CR increase. For this engine the cam used was a custom 276 hydraulic roller grind done to precisely cater for the cylinder head characteristics, CR and displacement involved. If the saving of about $250 is of interest then it’s worth noting that a hot street hydraulic flat tappet cam with a 280 duration will deliver very comparable results. My book ‘How to Build Max Performance Small Block Chevy’s on a Budget’ (available http://www.Amazon.com) goes into very precise detail on the cam selection for a given combination. It goes so far as to give the cam for your build to a precision equal or better than testing a half dozen or more likely candidates on the dyno.

If you are into small block Chevy’s it’s worth noting that the reviews on Amazon.com indicate this to be the top rated book on the market. The info it contains is highly pertinent to not only the home engine builder but also the small shop that needs to build cost effective crate engines.

Headers used were a set of street Hookers with 1- 5/8 th primaries and a 2-1/2 secondary (collector) 18 inches long. The carb was a entry level 750 cfm AED unit mounted on a Dart two plane intake. It is worth mentioning here that it is, for this test to be valid, important for the intake manifold is capable of servicing the needs of the engine at both low and high speed. This means a manifold that flow well by virtue of with efficient ports not big ones. The Dart two plane item met those needs. At each cylinder head change, which ran small to large, the intake manifold was re- matched to the bigger ports at the manifold face. Ignition was via a Pertronix contactless unit. These are low cost and get the job done well.

The Test Heads.

Here is a shot of Darts Platinum heads chambers with and without valves. The design of these heads is the result of a lot of R&D on both wet and dry flow benches and the dyno. If this technology is to be converted into results on your motor it makes sense to choose the right port volume for the application.

The intent here is to run four pairs of the Dart Platinum Pro 1 heads having intake port volumes of 180, 200, 215, and 230 cc. Regardless of port volume all these heads flow about the same cfm until some 0.400 inches of valve lift have taken place (see Fig 1). Even at 0.600 were the test engines valve train tops out there are measurable flow differences. Because of these differences are the result of a port size increase they are a legitimate component in our bid to investigate the overall effect on the engines torque/power curve.


Fig 1. For all practical purposes there is no great flow difference between these heads until about the 0.400 lift mark. At this point the superiority of the bigger ports starts to pay off. Even so those differences are hardly significant until about 0.500 lift. To tap into the full potential of the bigger ports a valve lift of at least 0.600 was necessary.


Here are relative sizes at the manifold face of the 180 cc port runner (left) versus the 230 runner (right).

Check out the flow curves in Fig 1. and you will see that the majority of the flow increases with increasing port volume occurs at the higher lift value. So much so that any test that did not put enough lift into the valve to access the extra flow at high lift would be totally skewed in favor of the smaller port heads…

We talk port size in cc’c but the reality is that it is the port cross sectional area that is the factor we wish to control. So why is port cross sectional area important? If the area is bigger the flow surely goes up and that’s what we want is it not? Sure the engine wants as much airflow as possible but much of the flow through-put depends on port velocity and the generation of pressure pulses. This means an overly large port can hurt power even though it may, on the flow bench at least, flow better. The question is how does this work out on the dyno?

Dyno Results.

So you can better see what’s going on here the torque and hp graphs have been separated. The effect any particular head has on low speed output can be more clearly seen by considering the curves shown on the low end of the torque graph. To see the effects on the top end check out the curves from mid to high rpm on the hp graph.


Fig 2. The dyno results tell us that smaller, higher velocity ports, favor low speed output. (black 180, red 200, green 215, blue 230). These results also show that going too big (blue curve of 230 cc port) on the ports, for the intended combination produces worse results almost everywhere in the rpm range.



It is easier to see what is working best at the top end of the rpm range by looking at the hp curves. Here we see that the 215 cc port (green curve) equaled or beat the 230 cc port (blue curve) everywhere thus proving bigger is not always better. Combining what we see from the torque curves and the hp curves the 200 cc runner (red curve) proves to give the best average numbers over the rpm range tested.

Inspection of the torque curves in Fig 2 show the 180 cc ports (black) turned in the best numbers up to 3400 rpm with a peak of 482 lbs-ft. The 200 cc port (red ) though marginally lagging initially proved stronger from 3400 rpm up where it ran up with, or close too, the bigger ports.

Considering the torque curves of Fig 2 and the hp curves in Fig 3 shows that for our spec of 383 incher, the 200 cc ports delivered the best curve. The 215 cc (green curves) heads made the highest hp by pumping out 478 horses as apposed to 457 for the 180 cc runners, 472 for the 200 and 475 for the 230’s. The price the 215’s pay over the 200 to achieve this 7 hp advantage is that they give away up to 10 lbs-ft of torque in the rpm range from 2300 to 3200.

As for the 230 cc port runner heads these, on our 383, failed to deliver any advantage anywhere in the rpm range. The smaller 215 cc port heads actually outperformed the 230’s everywhere! If the test engine was capable of more rpm or was of a larger displacement the bigger port heads would have paid off.

So how do you decide what port volume your small block Chevy should have for best results? Check out the chart Fig 4. This will give a good starting point for port volume selection for a 23 degree headed small block Chevy. A word of caution here. Do not overestimate the power you are likely to see. All that will do is lead you into a bigger port than would be optimal. This leads to less power than you had hoped for. At the end of the day a little too small is better than a little too big!

PortSizingFromHP.jpg

A final point, just in case you are wondering, with a slightly bigger cam and 10.5/1 CR the as-cast 200 cc Platinum Darts, on this engine, allowed it to crank out 500 lbs-ft and a tad over 502 hp.

For more in-depth David Vizard tech on hi-performance engines and cylinder heads in particular go to http://www.motortecmagazine.net

David Vizard, considered by many to be one of the world’s leading Performance Auto Tech seminar speakers, will be holding a two day seminar on 10th and 11th Sept 2011 at TPI specialties in Chaska Minnesota. If you want to get the benefits of a seven figure dollar R& D budget for the cost of a seminar ticket this is the place to be. As a true performance enthusiast you about owe it to yourself to check out this seminar at http://www.davidvizardseminars.com.

[87vette81big]

What I have learned Grumpy is most available cylinder heads & induction systems in use are not the limitation
on C4 SBC & BBC C4 Corvettes.
Its the available Exhaust headers in $500-750 range.
You can't get Big tube 1-7/8"-2" primary & 3-1/2"- 4" collectors.
Easily bought for other cars.
Dana IRS holds back power level that can be planted the ground on laynch too.
Till both solved Mustangs will continue to set records.
Corvette guys will dream only.
Talking about well north of 600 HP.
High RPM'S OF 7-9K.

[87vette81big]

Have to remember recession never ended.
Obama care will kill nearly all budgets.

Available 4-link kits cost $5k in a C4 vette.
Custom headers $2k.
$7k.
More than most C4 vettes are worth today.

Home made only answer.

[grumpyvette]

theres at least a dozen guys who will debate endlessly about what intake, manifold or cam, is the best on most cars, a few will discuss headers, but darn few seem too understand that the exhaust scavenging , cam timing and intake runner design are all part of a matching system, and if any one parts not designed to operate at max efficiency , in the same rpm, displacement and flow rates its going to reduce the engines power potential.
as always an hour , or two spent testing and finding out the actual FACTS of the engines operation rather than making random guesses, and a bit of research into your options ,rather than guessing and buying parts before you have verified the problem goes a very long way toward preventing you from wasting money and time!
what amazed me for years was that so many guys I talk with have NEVER even ONCE measured the engine in their cars EXHAUST back pressure, at wide open throttle so they have ZERO idea if they are dealing with an exhaust on the car that's hurting the engines power potential
and I doubt that number exceeds 10% of the guys I talk with , and of those few darn few guys ever do the math to design a better exhaust or do much more than complain about the lack of off the shelf options to cure the problem ...if ..IF they even understand it MIGHT BE an issue limiting the cars performance
if you select a cam thats designed to maximize power at lets say 6000rpm in a 12.5:1 compression 454, you need to select heads, intake, and an exhaust system that is designed to operate efficiently at the same rpm and power band.


one reason a properly port matched tunnel ram intake flows efficiently is a strait path to the intake valve, in the cylinder head from the plenum, match that to a well designed exhaust , high compression and matching cam timing,and you can significantly increase an engines ability to breath

READING THESE THREADS MAY HELP GUYS READING THIS
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[grumpyvette]

http://www.airflowresearch.com/articles ... arison.php