3.8l?

[Mountaineer]

I wasn't planning on it, but the guy does his own machining, and many people on the Z31 forum trust the guy.

But anyway, I didn't think the heads would fit, I thought they would need to be 99mm as well to match the cylinder.

[nathancrx]

It isn't required to have the heads match the cylinder walls. It will affect the quinch area in the combustion chamber. (which is the area between the valve and the cylinder) And depending on the compression and the shape of the pistons(wether or not they have valve reliefs or if they are flat top) the motor may run better or worse with the heads matched up.
But overall it does sound like your on to something.. Especially if the motor could be stroked as well..
It would be nice to have a 4.0 and an upgraded blower on my truck..(dreaming)

[Mountaineer]

I imagined that the smaller heads would impede airflow? There would be an 8mm difference between the chamber and the heads, but I guess in reality that isn't a whole lot. I just figured the difference would screw with the compression ratio or airflow.