Correct me if I am wrong, but aren't aluminum heads on a low compression motor a poor choice?? The thermal properties in effect lower the compression by reducing the heat.
I have no doubt that this is true, and to be honest I hadn't even considered it. I spent the whole morning thinking about this. It makes sense to me... it's not the compression per say that is reduced, it's the cylinder pressure during the power stroke, which torque and horsepower are 100% dependent on. If heat is dissipated more efficiently by aluminum heads, then chamber pressure will be reduced due to the lower temperatures. The question is, by how much?
In my case, I am replacing my old cheap Summit brand cam with a Hughes Whiplash cam, which is specifically designed to maximize dynamic compression, and therefor chamber pressure, on low-compression engines. I think that this cam alone will more than compensate for any loss due to increased thermal efficiency. Not to mention that the heads have a closed chamber and will increase the static compression ratio by about 0.7 points.
Still, all other factors equal, I would probably make more power with this combination of parts and a set of 915 heads ported to flow as well as the Stealth heads. But it makes no difference in the end because I only plan to run this setup for a year or two while I find another 400 block to build into a 470 stroker! When I finally get the bottom end done this thing will be about 10.5:1 and the engine would probably not be very happy with a set of 915s at that point.
