Compression ratio Q's m20b25 vs m20b27

[h82crash]

Has anyone cc'd the heads of a seta and a i head. I thought the seta combustion chamber was the same as the i's. My question is; if the c/r of the i engine is 8.8:1 how is the seta 8.5:1 when the piston rises higher than the i piston?

If I put the head if the i engine I have, on top of the seta block I have, the c/r will definitely be higher than the stock i engine. The squish is obviously smaller.

TKS

[jmc1590]

The Seta piston doesn't rise higher than a B25's piston. It actually sits about 0.5 lower at top of stroke. (Remember: the eta uses a 130mm rod, the B25 a 135mm rod.) Additionally, according to some Mahle information I found, the Seta piston has 3.6mm of dome, compared to the 4.2mm on a standard US B25. Less material in the combustion chamber = lower compression.

[h82crash]

Sounds logical and my eyeballs are out of calibration to tell the difference in dome height, but the seta pistons I have poke out the top of the block about 1.5 mm at the edge. The i block I just tore down, the pistons stop about 1 mm below the top of the block. Hence my bewilderment.

Ok, I was looking at the i block with the head gasket stiil on, DUH!