So, what is my best bet as far as carb selection goes on a setup like this. 1975 455 balanced and blueprinted (464 CID) -heads shaved and converted to stage 1 (no port work) -JE 10-1 pistons with an estimated total compresion ratio of 9.8-1 -crower hydrolic cam .507 intake, .525 exhaust 234, 245 duration at .050. -Eldebrock intake -1.6 -1 roller rockers msd distributor msd 6al box I currently have a 750 holley vacuum secondary on it, is this enough or am i a bit small. Also if anyone has any guesses what this would run in a 65 skylark, turbo 350, 2500 stall and 3.55:1 gears with slicks. just a guess is all i am looking for thanks bryan
I would go with a worked 800 cfm Q jet. I would bet that you are running a bit lean with that 750 on it.
Bryan, In my opinion, the carb you are using is fine for your combo. I am currently using a 750 double pumper with the following mods: 11.5:1 compression SP1 intake very well ported Stage 1 iron heads SP4 cam roller rockers. I have tried a 850, and a 1050 with no great improvements. The 750 is very sensitive to jet changes because it its small venturi size. I run 76 jets in the front and 84 in rear. The Buick has such a weak signal, that unless you are running big heads and a single plane intake you will not benefit from a bigger carb. Hope this helps. Rob
Brian......Like Rob said, your should stay with a little smaller venturi type carb especially with the auto tranny and that convertor........I would reccommend installing some down leg boosters because your carb has the strait legs and they really hurt flow....The down legs will pick the flow up almost 30cfm and with some work in the metering blocks and adding a secondary metering block you would have a great carb........Let me know if we can help......Jesse @ BIGS!!
Jesse from BIGS really knows what he's talking about. I think I was the first to try one of their carbs last year. I love it. I got one of their Stage 5 Holley 950HP's. Can't say enough about the thing. I picked up .24 in the quarter and it runs smoother. They really know what they're doing there.
IM NO EXPERT, but useing car math fomula, a good flowing 464 tunning 5500 rpm needs a 740cfm, at 6000rpm needs 800cfm, and at 7000rpm you need 940cfm. bigger carbs look cool and if tunned right your car will run fine, just more $$$$ and sometimes will cause bad gas milage, i have always found my cars to run better and have better responce when the cfm is match to the combo, i run a 800 qjet on my 462 and it spins up to 6000rpm nicely, many guy are running mid 12s to high11s with combos like yours, you should consider some head porting, the key to power in these buick is in the heads, just my 2 cents
QJets have great gas mileage and awesome throttle response. I had an edelbrock and kicked it out the door when I couldn't make it work like my QJet.
My own feeling was that Buick used the 800 cfm carb for a valid reason...I think they put more man-hours of research into than I have and they probably knew what they were doing. I always thought the real difference between the 'proper' 800 Buick Qjet and a carb from the aftermarket was that the Buick Qjet was specific for the engine, while the aftermarket carb was a generic carb. I wouldn't trust the engine cfm generating formula, the Buick 455 has a different intake velocity than a lot of more popular engines. If you know what you're doing, you can tailor a generic carb for the engine, if you don't, I would suggest sticking with a carb approximating the cfm of the original unit at least. With my own experience, although a nice carb, the Edelbrock Peformer 800 that I have now is not as good a performance carb for my 455 as my old 800 cfm Qjet. The throttle response is way different and when I used to open my secondaries it was like the car downsifted again. Not so with the Edelbrock. Nice carb, but not the one I should have choosen.
I have a 950 Holley that sits as a spare to my worked up 800 Q's The Holley works better at the track IMO, but the small tradeoff in high end gives back a MUCH better idle and low end throttle response. I'm currently on a very similar 464 buildup and will be going with the 800 Q jet. Up the idle ports, dill out the seondary well tubes & primary feeds as listed in Doug Roe's book and you'll really have something.
