- - Carb help
02-07-2011 06:55 PM
I have a 283 i just built, Basically stock except for cam and roller tip rockers. I put a crane cam .502/.502, 294/294 duration in it and found the WCFB carb does not work due to lack of manifold vacuum to hold down the metering rods.(385 CFM) I bolted on a 4GC carb and it runs a bit better. I can get it to idle correctly under 1200 RPMs. The idle screw is turned to the point the idle transfer slot is uncoverd and the boosters start to pull fuel . Its originally from a 348 engine, so CFM isnt an issue. The cam was intended for higher RPM(3200-6400) in a stock car. I need some input on using a 4 GC on this motor. OR should I change the intake to use a AFB or Q-jet? Its a semi-stock 57 chevy...I didnt want to modify the car too much under the hood.
02-07-2011 07:44 PM
The issue you have is too much cam, not enough engine.
To make it idle without pulling from the boosters you`ll have to advance the spark timing alot and likely drill holes in the primary butterflies.
When you move up on cam size, the rest of the engine has to go up with it. Cylinder head flow, compression ratio, exhaust system, ignition system, intake system, transmission and rear gears. You can`t just stuff a big cam in a stock 283 and expect it to run right.
02-07-2011 07:44 PM
Sounds like you went over too much on the cam.500 lift on a 283 with stock heads.Are you using this for race or street ?
02-07-2011 08:07 PM
Street car with 4.56s and a 4 speed.
02-07-2011 08:13 PM
Sharp car.I have a 55 post Delray BB 396 4 speed. But anyway back to your problem I really think you have gone just way too much on your cam.Were you just going for something with a good lick to it?
02-07-2011 08:38 PM
Id hate to have to tear out the cam and lifters now. Is there any other away around this mess? I just had the car painted. The only way i fix it is remove it and install this 348 ive been told is for sale. If that fall thru I want to finish my 302 project for it.
02-07-2011 08:43 PM
Wow your going to have to drive the hell out of the car with that cam and it still won't make you happy, just change the cam to one you can enjoy that matchs the rest of the engine. :nono:
4 Jaw Chuck
02-08-2011 12:37 AM
A Double pumper Holley will work better for that big a cam, still won't make that heavy a car move out of its own way unless you cram a lot gear into it. Way to much cam for that small a motor but a Holley will work better than the alternatives you posted. If you want to keep the cam you best get some headers on it and drop your gear ratio to 4:56 or so, that a lot of metal to move there. No matter how you slice it a stock style rebuild for that large a cam with stock heads and cast exhaust manifolds will be a dog.
Seriously, a cam swap would be cheaper and easier and be a lot more enjoyable to drive, try something in the 268-272 duration range...it will still have a decent idle and still have some torque to move that weight around.
Nice car BTW. ;)
02-08-2011 06:42 PM
Thanks for the input. Unfortunatly I wasnt thinking when I installed and degreed the cam in the lil engine that might. Im used to building larger engines that really breathe. I got the car to run better with a edelbrock carb, If I can lean it out thru the power valve curcuit it'll run better also.
I shoulda put in that 348!