switching heads

[micheal]

I have 1977 360 that i want more power out of. I found some heads off 1968/69 amx 390 or 343. The exhaust ports are retangular mine are dogport. the cast number on the heads are 3188558-2. I was wondering if these heads would be a good upgrade.

[bigblack'74]

i believe they a good upgrade are but you need an intake off a 68 or 69 because the center intake holes are different, and you need those exhaust manifolds too, where in iowa r u from?

[talntar]

and you would get rocker studs instead of bridges.
another pluse

[micheal]

I'm from Cedar Rapids. so my edelbrock torker intake wouldn't work.

[RBJ]

First off.... there a few things to consider. You can redrill the instake to fit the different mounts. But fore most you will have drill out the head bolt holes to accomidate the larger 1/2* studs that the 70 and later heads used. The heads are also smaller chamber size so your compression will go up meaning you might have to run premium gas to keep it from pinging to death. You manifolds will not bolt up (well they will bolt UP) but they won't seal properly, honestly IMHO it isn't a good upgrade to do, not to mention on the exhaust side they flow about 30% less then the heads you have now.

[Rande]

The later heads with the dog-leg ports flow 50 percent better than the early rectangular port heads. If you install your early, rectangular port heads, you are going backwards.

My factory Hi-Po book shows those heads as having the small combustion chamber (good for higher compression), rectangular ports (bad for air flow), and the smaller 1.62" exhuast valve (also bad for air flow).

You would be better off sticking with the later heads with the dog-leg exhaust port, and bigger exhaust valve. The only thing you give up is the higher compression of the smaller combustion chamber. Unless you are building an extremely high output engine, that loss of compression won't hurt anything. If you need the higher compression, use different pistons because the loss of the dog-leg exhaust port and its larger valve will hurt performance far more than a bit of compression.