thanks alot guys i appreciate your help i though the carb was ok and yes it stiill has points, but ive had the dwell set and the timing adjusted, yet the car still stumbles. so i bought a vaccum secondary rebuild kit at orileys but i dont know if its universal or not, they said it was but thier all idiots there.
No such thing as "too big" when referring to carbs. Especially Holleys. PaulS made good points. One more to consider is that if you're using a dual plane intake manifold, you can get away with more carb than you can with a single plane. We always ran a 750 or 850 (I ran 830) on my old '74. Ran fine. I also used a 600 when it was turbocharged (blow through). On blow through stuff it seems that most use a smaller carb for whatever reason.
I hope it is an actual Holley kit, a lot of the cheap generic rebuild kits are of not very good quality.
Just an fyi, A rebuild wont help it if it needs to be adjusted. I just recently worked on one that a guy had several people rebuild and couldnt fix it. Just needed a bigger squiter.
The biggest problem here is the blanket statement "a Holley 600 cfm carb is way to much carb for my 302". There's more factors involved than just engine size. Car weight, trans, rear gears, engine mods, intended use, all come into play. I know of a guy that runs a 800-something cfm Holley on a 289 and has great street manners yet pulls like a bear to 7500 rpm. You have to spend some time a learn how to tune them. Buy a book and read it. One aftermarket carb builder likes to say "It's only too big once it stops properly metering fuel".
thanks for the input again, and yes it is a real holley kit. and if i offended anyone in the orieleys comment im sorry but i wouldnt say it if it werent true scratch that theres a guy named ray who is smart and acctually knows what he's takin about.:bananaman
A 600 might not be too large for the 302 but I bet the 450 cfm would meter the fuel more efficiently. If both carbs were set up and tuned the best they could be both would run well but I bet the smaller carb would get better mpg, have a cleaner idle and a crisper throttle response. I have a plain jane 1850-600 cfm on the mild 460 in the F100 and it runs better than a tuned 750 I had on there. On top end the 750 would probably walk away from it but innormal everyday driving and a few red light fast escapes I like the 600 better. clint
Exactly the point I was trying to make, Clint. DEFINITION: expert, prn: EX SPIRT; EX - after, has been - spirt - drip under pressure. Alternate def: anyone more than 50 miles from home speaking on any subject to a number of people who wish to believe the facts as given - regardless of the actual truth of the facts. So I am a has-been drip under pressure or at least 50 miles from home ----- OK Right now I am both!
So then an even better solution is to just keep the small stock 2-barrel? Out of the box, yes, the smaller carb will obviously have a stronger signal through the boosters. But the large carb can be tuned to meet or exceed the smaller carb's efficiency. If you want efficiency througout the entire rpm range you need a carb that can satisfy the engine's air demand without causing a pressure drop through the carb. BTW most of the formulas you see that calculate this, even Holley's, are very conservative. For a real eye-opener on how your engine runs and what it likes, drive around for awhile with a vacuum gauge connected to full manifold vacuum. Normal driving and full throttle blasts. Give some thought to engine pumping losses, trying to breath through a straw vs. breathing through a garden hose... Which requires the engine to work less hard and accelerate easier? Now think about why Holley even came up with annular discharge boosters...
The 600 cfm four barrel will have smaller venturiis than the 350 two barrel. It will have a stronger signal through the primaries and thus better throttle response as long as the secondaries are vacuum operated.
I agree about the breathing through a straw but when you add having to also meter fuel then that adds something that I surely don't know how to talk about. I am just a dumb ol country boy that has messed around with Holly carbs for 20 or so years. lol clint
I didn't call anyone dumb, and I've worked with Holleys, Rochesters, and Autolites for over 35 years. The simple point I was trying to make is that you can have very good results with carb that 99% of the sheeple think is too big if you know how to tune it. Holley recommends their carb sizes very conservatively. They want everyone to be satisfied who just bolts on a carb, sets the floats, idle mixture, and curb idle speed. Yes, their recommendation will probably run just fine but your leaving a lot laying on the table by not using all of the tuning capabilities of the carb. When you do that you can run a much larger carb than what is normally recommended and have the best of both worlds. But you have to study and tinker and experiment. Wait! Doesn't that describe hot rodding? And yes, you have to consider metering problems with the bigger carb. That's why I threw out the comment in my previous post about why did Holley develop annular discharge boosters. To get better atomization and properly meter weak depressions (ssignals) across the booster.
I suffered with a 1.12 venturi 4100 for a while (parts store screw up). They flow around 600 cfm. I recently put on a new 1.08 4100 autolite that flows about 480 cfm....big difference. Better idle, throttle response, and mileage. 302 by the by.
