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I'm working on rebuilding a d16y8 and need some advice on cylinder specs. I think I already have the answer to this, but looking for confirmation or opinions.

I'm using a 2mm head gasket and 9.0:1 CP Carillo pistons, which together should bring the compression down to around 8.3:1 based on calculations using zealautoworks calculator. Stock compression ratio is 9.6:1

I hand (drill) honed the cylinders on this engine which brought the cylinder diameter up to the service limit. I did a compression test and each cylinder gets around 95psi. A new stock engine should have 135psi.

8.3/9.6=.864 * 135 psi ~= 116 psi

Based on my calculations I should be seeing about 116 psi, so I'm planning to take it apart and overbore the cylinders to 75.5 mm and use corresponding pistons.

Can anyone confirm that this is indeed the correct thing to do and my calculations are good?

One other variable I didn't account for is that the head gasket cylinder openings are 75.5mm vs 75mm cylinders, which will add a small amount to the combustion chamber volume as well.

Thanks!

p.s. I'm taking pics and will try to do a thread after the build is complete.
 

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Update

I just put some oil in #1 cylinder and re-did the compression test. It went up to 105psi.

This is a compression test outside the engine using an old starter which is not turning the engine over very fast, but it does seem to be stabilizing aroun 105psi.

I'm also fairly confident that the valves are making a good seal, at least they better be cause I spent about 1 billion years lapping them. Also adjusted valve clearance before performing this test so they should be fully closed.
 
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