Head selection

[eoseitz]

I've been posting a lot lately, but with the warm weather I've had a lot of time to work on the 74. I was wondering what some of you would suggest for a good head upgrade. My car has had the motor swapped out. It's a 76-77 LM1 out of a camaro. The specs are below:

Block	3970010		2 bolt main
Crankshaft			cast iron
Cylinder Head	333882		1.94/1.5" Valves, 75.47cc
Cam	14060651
Intake	14014440
RH Exhaust	346248
LH Exhaust	381863		could be 361863

The previous owner installed an Edelbrock performer intake, performer 650 carb and possibly a mild cam. I'm not sure of the cam size. I recently installed a new HEI tach drive distributor which probably won't make much of a difference.

I'm guessing I want to get 202 intake 160 exhaust to get better flow. The stock heads are 75.47cc so a smaller combustion chamber of maybe 64cc would up the compression and add some decent horsepower. I honestly don't know what the exhaust runners are for. Any info on this? I'm about to order some headers to reduce any bottlenecks in the exhaust system. I'm running straight pipes back to resonators.

What would be the best brand of headers for a resonable price? I'm wanting to get into the 350 HP range. My stock LM1 is only around 160-170 HP. I've heard votec heads are pretty good, but I already have an intake and valve covers and carb and don't really want to buy new ones. Also, would I need a more aggressive cam for heads in this range?

Thanks for any help.

 

[eoseitz]

Ok I did some more research and I think I understand the intake/exhaust runner concept now. For the exhaust it's the space the exhaust gas travels until it reaches the exhaust manifold? The intake/exhaust valve are how big around the valve are obviously. The bigger they are the more air/exhaust can go through. The combustion chamber is where the air/gas flames and causes compression on the pistons. Some would smaller intake/exhaust runners be better. I'm guessing smaller ones would be better for high rpm power such as sports cars? Larger ones would be better for trucks that need low end power, because it takes the air longer to move through them?

 

[spikebot 81]

The choices available will make you dizzy. Your biggest concern should be what shape is the bottom end of the engine. New heads and cam would put a major strain on the lower portions of the motor. This link is many years old but gives a idea of some HP combos:

Ryan's Small Block Chevy Stroker Engine Combo Page

 

[Crimson Thunder]

Definitely consider a 64 cc combustion chamber as that Camaro motor probably has dished pistons. Stay away from any head that has an intake port larger than 190cc. For a cam,look for something with an intake duration at .050 around 218 degrees. Best to call your favorite cam company to get a recommendation.

 

[paz72vette]

If you decide to change heads, make sure that your accessary brackets will hook up without modifications.

Cheers

Vito

 

[TimAT]

When you start getting into port sizes things can get interesting. A small to medium port (intake) will flow faster(port velocity) than a larger port, but since it physically cannot get more air thru it, it will limit top RPM. On the flip side of that, the smaller ports will produce great torque at a lower RPM. TO get the selection correct, you have to be totally honest with yourself. IF you're planning on making big power at high RPM, then you'll need bigger ports. Big ports at low RPM and there's not much torque until you start getting the RPM up.