Looking at a 2008 M1152 with the 6.5L & reading horror stories about cracked blocks, broken crank, blown head gaskets, cooling issues, etc.. Were improvements done along the way and by 2008 these motors are better than the earlier ones? Thanks

 

By about half way through 2000 they went to the "heavy block" and most of the engine issues were resolved.

 

Do you know what upgrades were done? Biggest thing I read is PMD relocation & cooling issues with older 6.5s

 

PMD relocation is easy. Gets the PMD out of the valley of the motor. The heat and vibration is what kills them. Heavy block had better coolant circulation so it fixed the overheating/#8 cylinder issue. Keeping the cooling stack clean and debris free is about the only thing you have to do to help keep them cool now.

 

Old 6.2 had woodruff key issues on harmonic balancer.

GM 6.5 had cooling issues.

GEP blocks seem to be more robust. Better alloy, better cooling. Valve seats are thin.

P400 engines are stout and take abuse. Water jackets are bigger. Valve seats are thicker. Alloy is better. Lower end is built in skirted.

My associate Eric has an old supposedly crappy 6.5 turbo and has almost 300,000 on the odometer in his M998.

I seem to recall an expression that “life is a bunch of chocolates.” You get what you get.