lumpy

[blowmestrokeme]

hey motorheads, how big of a cam can i use in my belvy, it has a 383 non stroker with flat top pistons, i just bought some aerohead 906 heads they can handle up to a .509 lift (i think) i have a .478 lift now.
i don't wanna get new pistons.

[rampage_82]

This is what Don Dulmage says about the 383... I don't know if it's gospel, but he is a pretty sharp cookie when it comes to B mopars....

Building a 383 Mopar is very similar to doing a 440 with a couple of notable exceptions. In a short stroke motor the piston moves less distance for the same amount of crankshaft rotation in degrees. In the 383 which has a 3.38" stroke it means the piston doesn't get out of the way of the valves quick enough. If a flat top piston such as stock type or the TRW style forged replacements is used and the heads are cc'd or even planed then the valve to piston clearances are too close for even a MP 509" cam and minor flycutting must be done. That is no big deal to shops used to doing it but many folks live in an area where the machine shop, while good, is just not set up for this type of work. (Remember not everybody lives in downtown LA) In that case it is probably wise to invest in a set that already have flycuts in them. While it is virtually impossible to overcam a 440 when it comes to duration the 383 is very sensitive to it and so duration must be kept on the conservative side. If you use the general guidlines given for small blocks you won't get in too much trouble. The MP 509" does work fairly well in these engines although I am sure it is not the ultimate but it is much much too mild for a serious 440. The 383 will make serious HP but will do it at a higher RPM than the 440. That is because the 440 and the 383 use the same heads and similar intakes and so are capable of passing exactly the same amount of air. (Same heads, carb and intake = same amount of air) For a 383 to pump the same amount of air as a 440 it would have to turn 115% higher.
IE A 440 at 6000 rpm pumps 763 cfm
A 383 turns 6888 rpm to pump 763 cfm
Recently we built an original 64 383 for car collector Glen Cole. He wanted a hot street engine for his 64 Plymouth Sport Fury and it had to be a 383. (I don't know why, I just do what I'm asked) To make a 383 perform well you have to take advantage of everything possible and leave no stone unturned but if you get too rambunctious you will destroy the streetability. We still have to do a serious strip flog on the set-up but it has now seen quite a few street miles. A recent pass down the quarter with no burnout, closed headers, leaving from an idle and letting the trans shift itself gave some timeslips well into the 13s. Our goal is to get it to turn a 12 anything in street trim and I think it is well within reach.

[rampage_82]

Also I don't think this has as much to do with the lift of the 509 cam, as much as the duration, or more importantly the duration at .050.. JMO

[JVMopar]

You'll definately want to check your piston to valve clearence no matter what cam you choose. You need 0.100" clearence.

[kllrbee69]

Will you be spending alot of time in the upper rpm range? If so, might as well go big. I think the MP purple 509 is like 248-250 duration at .050, and its like a 3000-6500 rpm cam.
I personally would go smaller. Something in the 225 dur. range with 112 LSA would give you much better low end. 383's always perform great in the upper ranges anyways, so I would do all I can to try to get my low end dialed in.
Also will you be degreeing the cam?