Heres a final model. All I changed was the head CC to 72cc360 heads, and a stock bore teener with .001" negative deck height pistons. Basically KB167s and a little deck shaving. Your still at 8.65-1 CR. Barely better than a stock teener, and this model is with better pistons.
Want to talk about port velocity. Again bigger isn't always better with a 318. A 360 has a 3.58" rod ratio. They couldent go any bigger piston diameterwise, so a 360 for lack of a better term is essentially a stroked 340. Same bore, longer stroke. And a 340 which has a 318 rod ratio is essentially a 318 with a 4.010" bore. Now theres other stuff to these engines that make them what they are, but the basics are essentially what I just said.
So this being said, you have a larger 4.010" piston surface area, and 3.58" long stroke, and this takes advantage of bigger valves, larger ports. and runners. It can pull in a larger volume of air without slowing down port velocity.
340 can do this as well but to a lesser extent, because of the same 4.010" piston surface area but makes due with a smaller 3.31" rod ratio.
Now the lowly 318. It has an even smaller 3.910" bore diameter, smaller than the 340, and 360, and the same shorter 3.31" rod ratio as the 340. It cannot draw near the intake volume on the down stroke as a 340 or 360. To keep port and runner velocity up, you have to make these areas a wee bit smaller. Besides ending up with a horrible compression ratio, This is the other reason why dropping 360 heads, and intake on a stock compression 318 is a horrible idea. Even if it had zero deck flat top pistons, your CR gain would be marginal over a stock 318 CR.
There is 1 exception to this rule in regards to port velocity. Turbos and supercharging. Stick them 72cc big valve 360 heads on a stock 318 with them shitty stock pistons, and put a turbo on it. The engine doesnt care how big them ports, and runners are then, because it's getting force fed, instead of relying on the intake stroke to pull in air volume.
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