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Sectioning the block also allows us to see if larger head studs can be used safely (beyond a drag race application). The particular piece also allowed us to see how water flows into the block from the water pump which BTW can be vastly improved.
We had several cylinder heads sitting around from the cylinder head development days also. There were a couple of both EVO 8 and 9 heads because they were used to study a core shift problem that contributed to wall thickness issues of our original CNC exhaust port. Core shift is something that happens in old school mass production castings where the sand cores shift in the tooling. When the alloy is poured into the tool, the “shift” of sand cores causes the hollow areas of the casting to be inconsistently placed in reference to a datum point. In most modern castings this ordinarily isn’t a problem and we usually see less than .040″ of core shift, but with the 4G63, we’ve seen over an 1/8″ (.125”) of core shift. This makes it tricky when porting via CNC.
I sectioned both EVO 8 and EVO 9 heads becuase I was told by somebody in Japan that the EVO 9 cylinder head was superior due to the longer spark plug and better cooling behind the combustion chamber. Sure the 9 spark plug is longer and is able to bring more heat out of the chamber and into the casting which is then cooled by coolant, but that was already obvious. The area behind the chamber itself was unchanged. The castings are virtually identical. Like Chuck D said, “Don’t believe the hype.”
I wasn’t just cutting anywhere. We pre-determined the sections we needed to study and then I cut. Anyhow, I have some pictures somewhere on the server and I’ll add them later today.
