Hello Guys, I have a solid stock 383 bottom end, running a stock cast iron 4 barrel intake,Mopar performance roadrunner 280 474 110 purple shaft factory non hp exhaust manifolds, stock single exhaust, I plan on purchasing a new set of CC 516 heads, 2.08 x 1.74 valves from Aerohead racing, Besides ordering the hardened seats. Should I spring for the larger 2.14 x 1.81 valves for only $50 more or would that be a waste? The motor is going in my 65 C body convert, automatic, 323 rear. Just looking for more torque out of a stock looking motor.

With your set-up all you need are the 2.08/1.74 valves. 516 heads with 2.14/1.81 valves will be shrouded by the combustion chamber and the top of the bore. Now if that was a 440 the larger valves would be nice due to the larger bore. You'll get more torque out of the smaller valves with your set-up.

I'd change the entire exhaust system too. Let it breathe.

As said I would get some 68-70 HP ex manifolds & dynamax (sp) turbo muffs with in addition glasspacks alongside the rear leafs. those Aeroquip heads are a mass produced item & there have been bad reports (but the internet is the complaint dept so we do get the bad experiences, just sayin). Are your current heads OK? if so I would leave em be & possibly swap the cam (what is your SCR) & get a good torque converter. Some aluminum stealths might be a cost wise alternative (again what shape are your current heads) & you might eventually get a 400 block/440 crank for 451 cubes!. when done be sure to dial in your dist subsystems in order. EDIT Mandrel bends 2&1/2" system/X pipe.

I've heard some bad stuff on Aeroheads too.

Well I thought of the aluminum heads but the spark plug holes are all angled, Will the stock logs work with the Aluminum heads? I am done with the dual exhaust. I just bought a Waldon stock single exhaust system. having a convertible, The drone and being loud is over for me. My originals need a valve job and probably new valves and springs. I called around and the basic 3 angled valve job is $530! I rather spend a bit more and buy new.

If your local shops do quality work, having the originals refurbished for $530 might be the smarter choice.

IMO, the Aerohead rebuilt heads are better looked at as being a "parts kit", where some tweaking might be required.

If you're looking for more grunt, I'd look at a smaller cam too.

This. That cam is so not right for your exhaust system, and your goal.

I would go down a couple of cam sizes. You are at about 230° @ 0.050". I would look for something less than 220°.

I have to agree with these other posts. If you are dead-set on a single exhaust & want more low-end torque, then rebuild the iron heads you have, "maybe" some minor port work + hardened exhaust valve seats for sure. A smaller cam will give you better off-the-line acceleration too in my opinion.

That is a great cam if you are running HP manifolds and dual exhaust with something like 3.91 gears. If you insist on single exhaust and are looking for torque, you would do better with Summit's 6400 cam. Also, I agree that having your heads rebuilt is a better option. I ran a set of 516 heads on my engine and was sorely disappointed. It made more torque and power with the stock open chambered heads.