Hi, I have a B20Z1 "high comp" block and the original B16 head in my car was milled about 0.58 mm (0.023 in) - service manual states 5.589-5.593 in, and my head measured 5.567 in. The head service limit tab was not milled flat, so it's still over the service limit (can post a pic if necessary). I'm worried about the P2V clearance. I was told that around 0.03in is the maximum you could mill with the stock pistons and stock B16 cams (running at 8200rpm maximum to avoid any valve float). I know I can measure P2V but I was wondering if anyone built a B20V with a head with that amount of milling with no issues so I can plan my build beforehand. I know there are aftermarket pistons easily available but they raise compression too much for a mild street setup (about 12.8:1) and would force me to run E100 (it's either 87 or E100 around here). Running a 5 layer head gasket (like Cometic's 0.060) would still get me around 11.5:1 which is still too much for 87 and in practice would require E100 anyway.

 

Just use a thicker head gasket to begin with... add back the amount of material that has been milled off the cylinder head.

 

That is also an option. I could use a Cometic
​​​​​​.050 gasket, that would bring my compression to about 10.0:1. Which would be basically running a stock head (0.026-0.050 = -0.024 added from the OEM gasket). I wonder if could I go with the thinner 0.040 so the compression is about the same as the stock B16. Another option would be taking the pistons to the machine shop to notch the intake valve reliefs. What would be the the better option?