Got a 29 roadster on 32 rails, so it's light, running 383 stroker Chevy, with 285B Comp cam, runniing a Offy dual plane intake. It's for the street, so probably won't see over 4 to 4500 the majority of the time, more like in the under 3000 range. Which carb size and model to run? I'm leaning towards a Holly with vacuum secondaries, and electric choke, but that's not written in stone, I can use a manual choke if need be, but it's already wired for an electric. Presently it's got an Edelbrock, I can't get to it for a while to give you the numbers off of it, but, it just feels like it's surging, put my foot in it, and it's off like a ****d ape. I just can't get it to idle down to my satisfaction. I've used the timing light for the initial timing, then used a vacuum gauge, to set the timing, and then the idle jets. I've had Edelbrock's before with a little 289 Ford, and it was good to go right out of the box, but I can better tune a Holly, (I think they're easier to tune) Something else, I'm at an al***ude of 1300' Now don't confuse me too much!!! Thanks for your imput.
There was just a thread on carbs last week that had some good info in it. I have a SBC with an offy intake, 292 comp cam and Im running a Holley 650 double pumper. I think with that cam your going to want to use a little more RPM's. I really like the mech secondaries over the vacuum.
Do a search, this came up last week. There were two different formulas with slightly different results. The one that I remember is... CID x Max RPM / 3456 I have no idea what 3456 signifies, but it seems to work. It's telling me that my 292 is overcarbed, which I already knew. If you do yours, you come out with just about 500 CFM if you shift at 4500. If you change that to 5000 RPMs it says to use a 550 CFM...but I don't know if anyone makes one.
i thought that was 5150 or so rpms....? as for a carb....my dad has a mild 383 in his 61....ported heads....decent 280ish cam ....dual plane intake....currently has a edelbrock 600 on it.......works good for driving around.....but not worth a hoot when your standing on it....i would say a 650 double pumper....you might even get by with a 600 dp.....smaller always seems a little more responsive on the street....if you were going to be racing it.....probably a 750 dp.....nothing worse than big carb bog......well maybe big cam /big carb bog ....because you went cheap on the convertor.....hahha brandon
Close but no cigar, Jay - torque and horsepower cross at 5252 rpm. I think the 3456 is just a constant - there's probably lots more factors in the full equation, but they can be simplified to 3456. Back to the carb question. If you are really being realistic about the rpm you want to pull, you could probably get away with a 600 vac sec Holley. But your cam is pretty big and to reach it's potential, you would be better off with a 750 - probably a vacuum secondary (list #3310) would be fine in a light car with a dual plane intake.
When in doubt go small. Vacuum secondarys for the street by and large are the ****. I personally woudn't run anything biger than a 650.
I've just installed a 383 with a Comp Cams 274H Extreme and decided to go with a Holly Street Avenger 670 with adjustable vacuum secondaries in my daughter's car. Won't make as much HP as a bigger carb, but will be better for street driving a 3200lb 4spd car. Ol Blue
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