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I have a 1969 Nova with a 454 that is bored 60 over. I have a 280 magnum cam, 1970 open chamber heads, C 396 maniford, Holley 650 and a turbo 400 with a 2500 stall. The gear ratio is a 472 and I would like to install something a lot smaller. How small can I go with out hurting performace? The car is driven mostly on the street but I plan on going to the track a few times this year. The motor seems to stop pulling about 5200 RPMS so I think the 472 gear is too big for the 1/4 mile run. Any suggestions will be great?
If your combo is all done at 5200 your most likely to hit max rpm before the end of the 1/4 with 3.73 gears. That being said from what you describe of your combo the 650 carb is way to small. You should be running a 750 minimum maybe as big as a 850.That small carb might be whats holding you back. Id try a bigger carb even if you have to borrow one and see if it falls off still. If it picks up a couple hundred rpm you should be ok with a 3.73 gear. When it falls off does it just nose over or does it go into valve float? That cam should see 6k easy without falling off real badly.
The motor pulls good to 5200 RMP after that it pulls a lot slower. It will pull to about 5500 or 5600 before it stop pulling. I have a Ford 9'' in the car. With 373 gears what RPMs should I have to get down the 1/4 mile? Will rejetting the 650 carb help or is it just too small?
That is one steep gear for a big block! Even saying that, I'd first get a bigger carburetor, 650 is too small. Even with re-jetting you won't get the flow (CFM) you need to supply the air needed to support upper RPMs. Your combo needs air.
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