IT should be rather obvious but obviously is not!



IT should be rather obvious but obviously is not!

Postby grumpyvette » January 22nd, 2013, 4:30 pm

IT should be rather obvious that a great deal of the info you need to build a really efficient engine combo is easily calculated if you know just a few basics about what you want to build and the enviroment or power band its expected to operate in,but obviously is not! AND YES EVERY PART CHOICE EFFECTS YOUR RESULTS
your at the point in your engine build where you need to select an intake manifold and carburetor.
you know from the experience of dozens of guys that a 750cfm carburetor will work, reasonably well so you purchased one, but what intake type should you use? lets use some calculators to find out!
but what intake manifold do you need, single plane or dual plane?
I can tell you from experience that is RARE for a single plane intake to produce better AVERAGE power than a dual plane unless the cam duration exceeds about 240 degrees @ .050 lift AND the peak engine rpm exceeds 6500rpm
the basic operating range of most dual plane intakes on most 327 and larger SBC engines is about 1500rpm-6500rpm, while most single plane intakes are designed to operate in the 4000rpm-7000rpm power band but obviously increasing the engines displacement increases the air flow speeds thru the ports, the single planes shorter more direct port runner design, will flow slightly more air but it requires higher rpms to maintain the air flow rates needed for effective air flow inertia to effectively fill the cylinders, keep in mind this has a big effect on the rpm range that the cylinder heads and intake will work best in,but doesn,t necessarily indicate the power level your going to be producing, as smaller port head can produce impressive power in the rpm band they are designed to operate in, your usually working against restrictions,
as for example
your valve train components might limit you to 6300rpm, but your cylinder heads might easily allow your engine to spin 7000rpm and still produce good power with a different cam, or your cylinder heads could be restricting power but the intake and cam could easily operate at a higher average rpm range.
its up to the engine builder to match the power and rpm limitations of components used to allow maximum efficient within the restrictions

A CORRECTLY TUNED SET OF HEADERS , MATCHED TO A CORRECTLY DESIGNED CAM TIMING HAS A SIGNIFICANT EFFECT ON INTAKE FLOW AND CYLINDER SCAVENGING EFFICIENCY, EXHAUST SCAVENGING CAN BE 5 TIMES STRONGER THAN THE PISTON, MOVEMENT INDUCED NEGATIVE PRESSURE (VACUUM) IN THE INTAKE RUNNERS
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you will need to match both the port cross sectional area and length to the cam timing , while taking into consideration the engine displacement and intended operational power band to select the correct intake manifold design.
Im assuming you know a good bit of info and are concentrating on selecting an intake to match parts you already have, but obviously you can calculate almost any thing you need to know if you just know the engine displacement, port size and cam timing.
lets look at this a bit, lets take for example a rather common 383 that we want to build to operate up to 6300 rpm, where we have found the hydraulic lifters don,t allow you to keep control of the valves, on your previously built 383 or 350,so you know a bit of useful info, now lets say you are using better heads on this engine build, youll need to know your cylinder heads cross sectional area and the valve size and lift, because those factors will effect max port flow rates and port stall speeds.
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OK first step, you know the engine won,t rev with the current cam and intake past 6300rpm, but will that be true with the new engine?
HERES THE HYDRAULIC ROLLER CAM YOUR RE-USING
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a simple calculation shows that at max valve lift the curtain area of the valve is larger than the runner cross sectional area so the cams unlikely to be a huge limiting factor in the combos ability to make power, but its duration maximizes the power in the upper mid range not peak power.
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USE THE CALCULATORS

http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
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OK lets assume you measure your cylinder heads intake ports and you find they have a 2.2 sq inch cross sectional area at the smallest point
(BTW I CAN ASSURE YOU that if you want better PEAK POWER NUMBERS swapping to a cylinder head that flows at least 280 cfm and has at LEAST a 2.6 sq inch cross sectional area would boost peak power
you use a a calculator and find that peak torque should occur near 4100 rpm, WITH THE CAM AND WITH THOSE 2.2 SQ INCH PORT HEADS , and that ideal runner length should be about 20" long

peak torque 4100rpm
http://www.rbracing-rsr.com/runnertorquecalc.html

IDEAL RUNNER LENGTH 20"
http://www.wallaceracing.com/runnertorquecalc.php

PORT STALL =6300rpm
http://www.wallaceracing.com/chokepoint.php

port velocity near 600fps PEAK
http://www.wallaceracing.com/lpv.php

FROM THE CALCULATED INFO it should be rather obvious that the longer runners in a dual plane intake and the basic operational range all point to a dual plane intake as being the best match, but its fairly close,if the peak torque was about 900rpm higher and the port stall was above 7000rpm,or higher, the balance point would more than likely favor the single plane intake, remember the single plane intake runners tend to be larger effectively reducing flow restriction.
http://www.summitracing.com/parts/EDL-7501/
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this intakes great between about 1500rpm and about 6300rpm. but really likes to have a bit better cam and head flow than stock, or your not going to get nearly its full potential benefits and of course a low restriction exhaust and headers

http://www.summitracing.com/expertadvic ... Calculator

http://www.summitracing.com/parts/HLY-300-110/
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this intakes great on a SBC between about 3700rpm and about 6800rpm IF YOU HAVE THE HEADS AND CAM TO USE THE FLOW POTENTIAL,On a non-supercharged engine, but its pretty much wasted with out a decent cam with at least 240 dur at .050 lift, and at least 10:1 minimum compression, and killer heads,that flow at least 250cfm at .500 lift OR with a supercharger with killer heads that flow at least 250cfm at .500 lift and a decent cam with at least 230 dur. at .050 lift and of course a low restriction exhaust and headers, but if you have an engine combo that does spend a great deal of its operational life in the 3800rpm-7000rpm power band you might want to look at it
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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
SINGLE PLANE INTAKE DIMENSIONS (you can learn a great deal by actually measuring INTAKE ports and runners ETC.)
http://www.edelbrock.com/automotive_new ... ions.shtml
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combining the info posted a 383 sbc has 47.8 cubic inches per cylinder divided by 2.02=23.7 on the chart above, so youll find cams in the correct duration range having a tight 105-108 lSA most efficient at filling the cylinders in many combos,

lets say we build a 496 big block with 2.19" intake valves,
496 divided by 8=62 cubic inches per cylinder, divided by 2.19=28.3. now look at the chart! you find youll need a rather tight 101-103 LSA



RELATED THREADS YOU SHOULD READ THRU

viewtopic.php?f=55&t=624

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

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http://mysite.verizon.net/vzezeqah/site ... ystems.pdf

http://rehermorrison.com/tech-talk-70-a ... low-bench/

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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: IT should be rather obvious but obviously is not!

Postby grumpyvette » August 23rd, 2013, 8:08 pm

yes reading the whole articles worth your time
http://www.circletrack.com/enginetech/c ... selection/

One cubic-foot of air at standard temperature and pressure (STP), assuming average composition, weighs approximately 0.0807 pounds. At STP, 13.5 pounds of air is approximately 167 cubic feet of air. If a Cup engine uses 170 lbs/hr of fuel at peak power (at 13.5:1 air/fuel ratio), that would equate to 2,295 lbs/hr of air. So, at standard temperature and pressure, 2,295 pounds of air would be 28,439 cubic feet per hour. This would be an astounding 474 standard cubic feet per minute. In this particular case, STP would be 60 degrees F and 14.696 psia. If you heated this air to a more reasonable (typical) inlet temperature, the volume would increase by the ratio of the absolute temperatures. In reality, this is an incredible amount of air to flow through a port.

Intake Manifolds
Intake manifolds are the primary tuning component for four-stroke, spark-ignited engines. Inlet runners function as organ pipes. The optimized length of a runner will provide wave reinforcement (energy) at the correct moment of the engine cycle to increase the pressure in the cylinder, before the valve is shut. This "wave reinforcement" improves the filling of the cylinder (volumetric efficiency) and thus increases torque and power. Wave reinforcement occurs over a very narrow engine speed range. Longer runners tune at lower frequencies, like large organ pipes, and shorter runners tune at higher frequencies (or engine speed). The frequency of the tuning point directly relates to engine speed as follows:

* Longer runners "tune" at low engine speed
* Shorter runners "tune" at higher engine speed

Here's one more point on intake manifolds. Airflow in an intake manifold is neither one-directional nor continuous. Remember this last statement; not continuous. Each time an inlet cycle begins, there is residual "energy activity" in the manifold. In fact, this is a subject unto itself. The point is that an engine's volumetric efficiency (as it affects torque output) is a function of how quickly and efficiently each succeeding cylinder can be filled, in the firing order. As the pressure differential builds between cylinder pressure and atmospheric (as influenced by engine displacement and rpm), the smaller the intake manifold's volume, the quicker it can contribute to v.e. Keep in mind that smaller volumes associated with this condition can become flow restrictions (and contributors to the mechanical separation of air and fuel) at higher engine speeds. You simply need to determine the specific rpm range in which the engine will be run and select intake manifolds accordingly.
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: IT should be rather obvious but obviously is not!

Postby grumpyvette » December 20th, 2013, 12:04 pm

horsepower is simply a way to express the RATE that TORQUE can be APPLIED, the faster you can spin an engine and still produce useable torque the more useful it is to use GEARING to allow rapid use of the power produced.

the formula for horse power is torque x rpm/5252=hp

thus
if your engine makes 500ft lbs of peak torque at 3000rpm,you divide that to find your making 286 horsepower

if you make the same 500ft lbs at 5000rpm, your calculations show 476horse power

make the same 500 ft lbs at 6500rpm, you get 618hp

horse power always equals torque at 5252 rpm.
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your component selection, displacement and compression, will determine the effective power band

viewtopic.php?f=50&t=422&p=518&hilit=horsepower+calculate+5252#p518

viewtopic.php?f=52&t=5078&p=18935&hilit=horsepower+calculate+5252#p18935

viewtopic.php?f=87&t=9731&p=37718&hilit=horsepower+torque#p37718

posting.php?mode=edit&f=69&t=9930&p=38054
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: IT should be rather obvious but obviously is not!

Postby philly » December 21st, 2013, 3:01 am

grumpy i was wondering with regards to the chart for choosing lsa based on cid and inches of intake valve, what benefits come from that choice? powerband? vacuum quality? why shouldnt i run one of those example motors with a different LSA? could you explain the consequences of and benifits of lsa choice? (i see alot more links and reading in my future) :lol:

by the way i feel like dennis hopper in apocalypse now when i say youve "enlarged my brain" with the information here
-phil

There's never enough money to build it right, but there's always enough to build it twice!
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Re: IT should be rather obvious but obviously is not!

Postby grumpyvette » December 21st, 2013, 9:18 am

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the purpose of the chart is to give you a fairly realistic starting point to select a cams lobe separation angle 'lsa'
keep in mind , with a given duration, as the LSA gets tighter the overlap tends to increase and exhaust scavenging becomes more effective at filling the cylinders, its that more effective scavenging during the overlap that allows the more effective fill of the cylinders, and the longer the stroke, and larger the displacement the more effective that scavenging needs to be to effectively sweep the previous charge of burnt exhaust gases from the cylinder,replacing them with a fresh charge, keep in mind the valve size is limited, so the curtain area gets restrictive as the displacement and stroke increase especially when you consider that at something like 6000rpm, the cylinders need to fill, ignite, and push out the exhaust gases 50 TIMES A SECOND

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viewtopic.php?f=52&t=1070

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viewtopic.php?f=55&t=10073&p=39779#p39779

you might find these threads below useful
most of the current low rise 4 barrel carb. intakes designed for street use fall in the 240cfm-260cfm range in stock out of the box form, the better single plane, intakes tend to run 20cfm or so higher, either style can be ported to increase the flow rates.
keep in mind the proper cam being selected and with matched headers and a low restriction exhaust can significantly increase effective cylinder scavenging, resulting in higher intake flow efficiency. Id also point out that my experience has been that the vast majority of people can,t read spark plugs to see whats going on during the combustion process, many have no idea how to customize an ignition advance curve or tune a carburetor, or properly regulate fuel pressure to save their butt!
Even fewer can clean up an intake plenum or port runners even marginally well.
Id also point out that a properly tuned dual quad intake can provide remarkable results especially the tunnel ram and cross ram designs , but theres so few people with the required skills or desire to learn the old school tuning skills that id bet 80% of the dual quad setups are far from ideally tuned so they got a less than favorable reputation. most of the younger guys think you tune a car with a lap top computer
viewtopic.php?f=55&t=444

viewtopic.php?f=55&t=109

viewtopic.php?f=44&t=623&p=834&hilit=camaro+crossram#p834

viewtopic.php?f=55&t=5175&p=25996&hilit=tunnelram#p25996
CALCULATORS
http://www.wallaceracing.com/calcafhp.php

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

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

http://horsepowercalculators.net/intake ... old-design



viewtopic.php?f=55&t=58

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viewtopic.php?f=55&t=4930

viewtopic.php?f=52&t=5537&p=16750&hilit=1206+1207#p16750

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viewtopic.php?f=52&t=462&p=11902&hilit=1206+1207#p11902

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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: IT should be rather obvious but obviously is not!

Postby 87vette81big » December 21st, 2013, 1:17 pm

I plugged numbers into your Lobe seperation Formula Grumpy.

Pontiac 455 bored .030 is a 462. 2.11" Intake Valve Pontiac RAIV Head 614.
About 101 Lobe Seperation Angle called for.

1965 Olds 425 , 2.00 " Intake Valve. A casting stock BB OLDS.
Lobe seperation Angle of 102 called for.

410 sbc my late friend built & left me to complete.
Lobe seperation angle of 103 called for.
Custom ground Crower cam in it.
Had no free time still
to Camshaft degree
& discover specs.
Want to this winter.
Have my Proform cam measuring Tool purchased this past summer.

The Pontiac 455/462's I have ran I used 106, 108, 110, 112 lobe seperatuon angles.
108 my Favorite from Isky Cams.
Super bottom end torque. Wants to Rev to the moon. Won't lay down in power.

Lobe seperation angles calculated not off the shelf material.
Custom ground only. Especially For BB Poncho & Ilds
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Re: IT should be rather obvious but obviously is not!

Postby 87vette81big » December 21st, 2013, 1:25 pm

What VE Are we calculating to Grumpy ?
87% , 95%, 100% ?

One Pontiac Racer from 1970 built a 455 short Rod combo.
6.25 " rod length instead of 6-5/8".
Used 95-101 lobe seperation cams.
Raced Pikes Peak & on Road Courses.
Installed in a 1970 Tran Am.
Legend has it was a Porshe & Ferrari Killer.
Untouchable.

Not arguing with you.
Just interesting.
Winter is here. I can read all links you provide in depth.
Chasing kids, can read only 50-60% in one sitting

BR
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Re: IT should be rather obvious but obviously is not!

Postby grumpyvette » December 21st, 2013, 1:29 pm

many factory ,produced and aftermarket cam designs are far more concerned with having a decent idle or being easy to tune than they are at maximizing the power potential, and if the ideal cam LSA for an application might be something like 105 LSA, use of something like a 110 LSA may reduce the peak power 5-20hp but gains you a bit wider torque curve at a slightly lower level plus a smoother idle, which is not always a bad trade-off on a street car that will seldom need or be run up in its max power range

as an example
If you build a 496 BBC stroker , designed to maximize power youll be using high compression and race octane fuel, built with the big 2.3" diameter intake valves , youll be expecting to spin it up at or slightly in excess of 6000rpm at near max piston speeds , youll be running a cylinder head with between 3.5 and 4 square inches of cross section, that flows close to 370cfm-400cfm, and a cam that has at least a .650 -.700 lift and about 250degrees at .050 lift or a bit more duration, and that would most likely require a 11:1-12.5:1 compression ratio and a good single plane or tunnel ram intake and gearing the car so it operates in the 4500rpm-6300rpm power band.
as you can see that might not be ideal on a street car so there will be compromises made, in some areas to allow a more useful low rpm power band and a bit lower octane fuel.
use of a wider LSA and a bit lower compression might cost you a few horsepower but it will make a great deal of useful power and be a bit easier to drive under conditions where your not holding the throttle firmly on the floor most of the time

USE THE CALCULATORS

http://www.rbracing-rsr.com/runnertorquecalc.html
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
thats 496 /8=62 cubic inches p[er cylinder, divide 62 cubic inches by 2.3" and you get 26.9 on the chart or about 102 LSa, youll generally find cams with 106 LSA to be about the tightest easily available so thats generally what I select if i'm trying to maximize the mid rpm power curve but keep in mind other factors
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RELATED INFO

viewtopic.php?f=69&t=5123

viewtopic.php?f=69&t=9047

viewtopic.php?f=69&t=1420

http://www.hipermath.com/engines/carburetor_cfm

use some serious components like TRICK-FLOW 340CC or AFR 335CC heads, some port and intake work, attention to the valve train details,a decent solid roller cam , and valve train,like a crane 138891, a matching tunnel ram , with twin 950cfm dominator carbs a good 8 quart baffled oil pan,windage tray,and put it on a 12.5;1-13.5:1 compression 496 BBC-540 cubic inch engine, add a vertex magneto,, add some tunned headers roller rockers, a rocker stud girdle, and some careful fitting, and you get an impressive race/strip combo,put it in a 2800lb car with a 4 link dana rear , a 4500rpm stall converter and 4.11rear gears,29" tall slicks,that won,t run worth crap on street octane fuel, but on 115 octane it destroys slicks
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: IT should be rather obvious but obviously is not!

Postby 87vette81big » December 21st, 2013, 1:55 pm

No.
I always chose All out Racing Cams Grumpy.
85-95 degrees overlap.
Idled 1,100-2,000 RPM.
Super Choppy idle a Badge of Honor & Privelidge.
Entire car has to shake.
Nail the gas & 1970-1/2 Trans Am Shaker Hoodscoop quit having an earthquake & moved far right over 4 inches
Electric trap door on back Wide Open sucking in fresh outside air in windshield high pressure zone.
Just want Race. Power.

Olds 425 street engine. Super torque stock.
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Re: IT should be rather obvious but obviously is not!

Postby 87vette81big » December 21st, 2013, 2:02 pm

100 % Straight race gas used too Grumpy.
110 motor octane.
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