ClTuner1

Does anyone know the specs on the J32A2 pistons? preferably the bore of the valve reliefs? im trying to combined the J32A2 heads and valves with a J30A1 block but don't know the differences in the reliefs

JarrettLauderdale

I know this thread is old, but I'm bored.

The P8E heads have a combustion chamber diameter of 89mm to match the J32 and J35 blocks they come mated to. The J30A1 (and all J30 engines) have an 86mm bore. Before valves ever come into the fold, you create a severe sharp edge around the edge of each combustion chamber.

Despite this, I've heard it suggested many times for people to perform the modification you propose. I can't say that I've seen it done, but I haven't seen anyone come back upset because they did it and it didn't clear valves.

So, onto the the reliefs. It doesn't matter what the reliefs are for a couple of reasons. One, the reliefs are just small dimples on the P8A piston. Two, number one doesn't matter anyway because the centering of the intake valves is different in an 86mm combustion chamber vs. an 89mm combustion chamber. They're offset by a bit.


My suggestion would be to swap in an entire J32A2 or even a J35A3. I'm building a high-compression J35A for my CLS6 right now and have tons of measurements for lots of different J-series parts that I'll post on the 2nd gen side when I'm done.