M42 Upgrade Ideas

[peytonnoel]

So I've heard conflicting sides on whether the M42 has forged pistons and rods, do they or should I replace them with such? I plan to turbocharge the engine, head gasket is getting replaced now, new head studs, machining, hot tank. What else should I look into doing while I have the engine disassembled?

[DesktopDave]

I've always understood that the M42 had a forged crank and rods, but cast pistons. The M44 is all cast. If you're lowering the compression ratio, definitely go forged. If you're keeping it stock CR, I've heard that a max of 6psi is advisable. I'm also told that Honda pistons are a good fit for turbocharged motors. Check out some of Warsteiner's posts for details.

I'd definitely replace the half thrust bearing with a full shell from an M50. I'd also be tempted to get a crank scraper. I think Ishihara has one.