Son has 72 chevelle, 327 30 over samll 268 cam. I was thinking about putting
a 500 edelbroc carb on it. Is this too small?
Printable View
Son has 72 chevelle, 327 30 over samll 268 cam. I was thinking about putting
a 500 edelbroc carb on it. Is this too small?
Here's a handy-dandy formula for sizing carbs - plagerized by me from other sources:
"One general rule of thumb uses a formula to determine the CFM requirements of your engine. It goes like this: You need to know the CUBIC INCHES of the motor. You also need the maximum RPMs the motor will be spun to. Finally you also need the VOLUMETRIC EFFICIENCY PERCENTAGE (VE%) of the engine. The first two items (CUBIC INCHES and RPMs), are relatively easy to determine. The engine VE% is another matter. If an engine could use all of the air it ingested, it would have a VE% of 100%. Many performance engines reach this level. Certain race engines can actually exceed this and reach a VE% of over 100% at certain points in their RPM range. Most production engines and most street performance engines have VE levels below 100%. In fact, stock, production, low performance motors will fall around 75%-85% volumetric efficiency. "
The math formula is:
CARB CFM = CID x RPM/3456 x VE
Therefore: 331x6000/3456 x .90 = 517CFM (or rounded up, a 550/600)
The 3456 is a constant - but darned if I know from where:whacked:
Man I had to think about that one for a while.Quote:
The 3456 is a constant - but darned if I know from where
one cubic foot = 12x12x12 = 1728 cubic inches per cubic foot.
One would think that is the conversion factor needed but -
At any given rpm only 1/2 the displacement is actually intake flow.
so you have to divide the total flow by 2 before converting CIM to CFM.
therefore -
CIDxRPM/(12x12x12)2 = CIDxRPM/3456
All depends on what you want the motor to do. I'll pass on Denny's own formula for maximum power, cubic inches times 2.Quote:
Originally Posted by rdobbs
If you're just looking for a good cruise carb, follow the formulas given above.
ussually my formula for a good cruise with a little get go is the closest size down from dennys power method... say a 351x2 is 702 so i'd run a 650... thats ussually a good way to get something that'll cruise well tune in easily but still pick-up when you want it to.... if you went with a 700 on that formula, it'd be a lil more work to dial it in, but it'd run at top RPMs a lot better
This is fine - if you have a car that runs only on weekends, and a quarter mile at a time. Most folks run their car to work, to the store with stop and go driving. This means compromise for driveability, fuel mileage and just plain driving enjoyment. A mild 331 CID Chevy(or any other engine) with a flush toilet size carb is NOT fun to drive. Bigger is not always better. Been there - done that with 750/780CFM 3310s and 950 CFM three barrels on BB Fords to name a couple of toilet sized carbsQuote:
Originally Posted by thesals
Formula?:eek: :confused:
I just look in the carburetor cupbard and pick one that looks like it'll do the job....:LOL:
Sugar coated, granola, fruit flavored, artificially colored and flavored or.....Quote:
Originally Posted by C9x
Ding,ding,ding we have a winner.Quote:
Originally Posted by Irelands child
In other words a 500 cfm carb will work great.
My opinion (humble as it is:rolleyes: ) would say that a 1406 Edelbrock 600cfm electric choke with tuning kit work would be optimum with a 500cfm part 1403 or 4 as a good second choice for all around driving. When I recall that my old F350/460CID had an approximate 500 cfm Holley on it, ran pretty good.
Denny,he won't go lean he will tend to go rich or the engine will go flat on hp and torque and fall off if it runs out of air.Quote:
Originally Posted by DennyW
Car will be a daily driver, no racing..rdobbs
Have to use the formula with the RPMS if your building it like that "302" thread LOL. What was it? 12,000 rpm 302 cid? how many cfms would that be?
cubic inches x max rpm / 3456
Yup....That formula has worked for many years, bet it still does, huh????Quote:
Originally Posted by DADNOVA
Hey Denny, that's for each carb on that tunnel ram, isn't it?????:whacked: :whacked:Quote:
Originally Posted by DennyW
How much RPM do you plan to buzz this 327 to ? If your going to stay within 5000 RPMs Id say the 500 is perfect. if your going to rev it closer to 5500 Id use a Holley 570, or if you dont care for Holleys, a 600 Edelbrock
Go with a Demon Carb. I've been through Hollie's and Edelbrocks by the boxes.
Bought 1 demon and have never touched it for years.:)
:)
Demons are great to, but Ive got a 770 Holley on my 454 that I havent touched since I put it on almost 4 years ago. John
Thanks guys for all your good info. I ran 2 500 cfms on my 383 smb chev
they did great. Have a 1050 dominator on my big block chev, it also does
a good job. I think I will go with a 550 or 600 on that 327 engine, as it will
probably never see much more than 5000 rpm, and i think I will go edlebrock.
rd