carb. CFM ?'s

rod · 03-07-2010, 11:46 AM

dusting my old AHRA stock class car off to go to the 'vegas super chevy race soon. since bracket racing is all tere is anymore....i will retain the car as is. it was legal [back in the day] to run any Holley carb.
so a bit of car background and then the question.
3550 w driver, 2.64 low 4 speed, 5.67 gear. 265 [+60=273]. old Holley single plane [300-1 maybe] currently running a 600DP.
the two quickest runs the car ever made [at two different tracks, years apart] were with a 750 DP. 'vegas is 2200', Bakersfield is 280'
the calcs show this engine needs a 600 CFM. are the calcs wrong, only ballpark, or are there other facts which influence the outcome?

thoughts/ideas?
thanks rod

Kegracing · 03-07-2010, 12:12 PM

Rod,

Most all calculations make the "assumption" of 100% efficiency. This is what causes some errors. Often what cars require and what they want are two different things. Your combo may only require 600 cfm, but is the 600 DP going to give you 600 good cfm? The 750 can do that a lot easier... While I am a stickler for matching a combo, as I have proven to myself over and over that more is not always better, this is not going out to left field. If you were talking about putting a 1050 on it, I would say no way. But a 600 to a 750 is a pretty easy to justify swap.

Put the 750 on it, and then jet it for the best performance. Just my opinion...

Good luck!

Ken

Pat Cook · 03-07-2010, 01:21 PM

Hey let us know what the outcome is, thanks.

Robert Simpson · 03-07-2010, 09:35 PM

Rod, I would stick with the 600, if you don't turn alot of RPM's 7500 and higher then it should be just fine. We run a super stock 265 with the wcfb and would love to have a 600cfm, LOL. Good luck and tell us your results, any pictures?

03-07-2010, 11:46 AM	#1
rod Member Join Date: Dec 2009 Location: Kingman, NW AZ. in the middle of the longest stretch of Route 66 Posts: 313 Likes: 0 Liked 20 Times in 15 Posts	carb. CFM ?'s dusting my old AHRA stock class car off to go to the 'vegas super chevy race soon. since bracket racing is all tere is anymore....i will retain the car as is. it was legal [back in the day] to run any Holley carb. so a bit of car background and then the question. 3550 w driver, 2.64 low 4 speed, 5.67 gear. 265 [+60=273]. old Holley single plane [300-1 maybe] currently running a 600DP. the two quickest runs the car ever made [at two different tracks, years apart] were with a 750 DP. 'vegas is 2200', Bakersfield is 280' the calcs show this engine needs a 600 CFM. are the calcs wrong, only ballpark, or are there other facts which influence the outcome? thoughts/ideas? thanks rod

03-07-2010, 12:12 PM	#2
Kegracing Member Join Date: Jun 2002 Location: Red Oak, TX Posts: 441 Likes: 0 Liked 0 Times in 0 Posts	Re: carb. CFM ?'s Rod, Most all calculations make the "assumption" of 100% efficiency. This is what causes some errors. Often what cars require and what they want are two different things. Your combo may only require 600 cfm, but is the 600 DP going to give you 600 good cfm? The 750 can do that a lot easier... While I am a stickler for matching a combo, as I have proven to myself over and over that more is not always better, this is not going out to left field. If you were talking about putting a 1050 on it, I would say no way. But a 600 to a 750 is a pretty easy to justify swap. Put the 750 on it, and then jet it for the best performance. Just my opinion... Good luck! Ken

03-07-2010, 01:21 PM	#3
Pat Cook Member Join Date: Jun 2002 Posts: 175 Likes: 0 Liked 0 Times in 0 Posts	Re: carb. CFM ?'s Hey let us know what the outcome is, thanks. __________________ 67 Ford Fairlane F/SA 749

03-07-2010, 09:35 PM	#4
Robert Simpson Senior Member Join Date: Aug 2004 Location: Jacksonville, Florida Posts: 807 Likes: 7 Liked 20 Times in 12 Posts	Re: carb. CFM ?'s Rod, I would stick with the 600, if you don't turn alot of RPM's 7500 and higher then it should be just fine. We run a super stock 265 with the wcfb and would love to have a 600cfm, LOL. Good luck and tell us your results, any pictures?