Hello,

This weekend I was driving along and suddenly a terrible metallic clatter from the engine!! Horrors. Only 3 cylinders of power, too. So Sunday I pulled the head and looked in. A few teeny dents on the top of the piston, and one decent one. The exhaust valve was also bent. But the offending piece was not to be found. The cam is a 'D' grind, so not exceedingly high lift. I'm just trying to figure out how big the piece of whatever was. Whatever it was had to get clobbered between the open ehxaust valve and piston at TDC of the exhaust stroke. Even though the B20 is a non-interference design, how close are the tolerances, anyway? Thankfully it's all back together and runs fine now.

Thanks.
--
Justin 70 1800E, 66 122E

You definitely ran something through it.
In my case it was a 5/16" hex nut and it was squashed down to about 1/8"
thick before it was done. There are more problems between piston and
head than with the valves because the valves are not open very far at TDC,
even with a wild cam.

Look through your intake system for missing parts. Mine came from an
air cleaner and I was 3 weeks figuring out where it came from.
You may have blown it into your exhaust and it might still be in your
muffler (if any).

Butterfly screws are one (rather limp) possibility.
--
George Downs Bartlesville, Oklahoma