I own Mopar!

[Bill Pritchard]

Originally Posted by njsteve

This is what happens when you put them in backwards (or swap them left for right bank).

That's EXACTLY what happened on my Challenger. It came with all 8 pistons the same from the factory.....IIRC, there is an offset on the piston pin of a few thousandths of an inch, the only difference between left & right bank pistons. Apparently when that engine was originally built either they were out of one type of piston or else someone just screwed up and put in all the same ones. Well, there is an arrow stamped on the piston head that is supposed to point forward. When I rebuilt the engine, being a newbie to 426 Hemi intricacies, I made sure to have all the arrows pointing to the front like the manual said. When I first fired it up I just thought the lifters were taking a long time to pump up (it was a 70 so it had hydraulic lifters). Ran for about 2 or 3 minutes before I got exactly what is pictured above in one cylinder Luckily it did no other damage....no scoring of the cylinder wall or anything major, just a lot of bent valves and marred piston tops on one bank.