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Carb CFM rating for 454

831 Views 2 Replies 3 Participants Last post by  Strider
I'm about to dive into fine tuning the carb on my mildly moded 72 454 with a LM-1 Wideband O2 AFM setup. A couple of local sages have opinioned that the Holley Squarebore 600 CFM carb might be too small for the engine. As we discussed it, they focused on how much the throttleplates would need to be opened at idle to flow the air required, and they thought that too much of the transition slots would need to be exposed.

Any thoughts??

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Just my $.02 here. I'm running a 454, somewhat modded(?).Well, Ok a lot!.
A 600/650 will work great around town and will have loads of low end because of the higher air speed thru the carb. But it'll run OUT of air way before the cam/heads do. It will lmit your RPM because it jut can't flow enough. Again (IMHO) a 750 to 850 will do a much better job for you. Some of the low end will go away (like a 454 needs more), bu it'll make up for it in the mid to upper ranges.

I like the 850 double pumper 4 corner idle for the 454. You can jet the double pumper down for good fuel economy, the mechanical secondaries guarantees they open when you want and the 4 corner idle can be set to idle in the 13.8-14 range that you want for a carbed engine.
The LM-1 will bounce around if you have a lumpy cam or any exhuast leak.
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