Join Date: Sep 2000
Location: Washington, Michigan USA
Does my 'ol heart good to see some intelligent discussion on carb sizing! I''ve been building SBC's for 30+ years, and people always ask why they run so well, then they get quizzical looks on their faces when I tell them I run NOTHING but 600CFM vacuum-secondary 4150 dual-feed electric-choke Holleys (#0-80145), generally on Performer RPM manifolds, whether they're 350's or 383's. Can't believe how many guys listen to the speed shop counter guy or read the dyno articles in the magazines and run out to buy 750-850 Holleys (or even Dominators, for crying out loud), and then all you hear is how their car runs like crap. DUH!! They don't bother to learn about air velocity, vacuum signal strength for metering accuracy, or anything else that really matters for daily driving - just those BIG numbers! (which are only there for a few seconds at WOT on a dyno under carefully-controlled conditions).
Also hard to convince the "big carb nuts" that the only reason the 302's came with a 780-800CFM Holley 4053 was that it had to be homologated that way as a production car in order to be used legally in the SCCA Trans-Am cars, which spent their whole life at wide-open throttle between 5000 and 8000 rpm - just like your street car, right?
Unless you run your SBC engine at 8000 rpm all day long (look out for shrapnel!), a properly-tuned 600 Holley is just right for 99.9999999% of your driving. Speed shop guys just LOVE to sell $600 carburetors - the 600CFM Holley #0-80145 is $265.00 (Jeg's), and the comparable-CFM Road Demon is probably just as good or better, at about the same price (haven't tried one of those yet, but hear good things about them).
Keep the good logic coming! (At least half of the posts in the "Troubleshooting" section would probably disappear without 750-and-larger carbs).
'69 Z28 Fathom Green