Finally got some news on a issue I was having with my engine. I had a excess of pressure in the crankcase which was causing it to blow the dipstick out and blow oil all over the engine compartment and header creating tons of smoke under the hood. Somehow I broke the ring lands of the piston, builder thought maybe a over revving thing . Fortunately it held together in the bore and there was no damage or scuffs to the cylinder wall. Got some new forged pistons. Chatted with another person and they had the exact same problem with the same piston , just a different size. First picture is mine , second is other person's .

 

 

Just curious, did he explain the logic behind that? Just wondering as a former mechanical engineer. You'd think the highest stress from over revving would be around the pin as the stress is a lot more concentrated there than the drag forces around the OD. Also interesting it broke on the middle land - You'd think the drag forces of the lower rings would be much lower than any other force in the chamber.

How high were you revving it?

 

Honestly I don't understand either, my car is equipped with a rev limiter set for 6000 rom ( msd 6 AL box) . He mentioned that if the top broke off it's normally due to not enough ring gap, which he did gap when it was assembled. There's a little spot in the missing piece that might indicate a bad casting being hyperutectic instead of being forged. The weird part is there was compression in that cylinder that matched the other holes. The only way I narrowed down the cylinder was to add air pressure to the hole and it only leaked when the cylinder was at a certain location. He said it was still one piece until he started to remove the rings. I'm just glad it didn't tear up the block .

 

Very interesting. Ive certainly seen a ton of broken top lands as you'd mentioned on the 3800s, so its so strange to see the middle one go while the top is intact. A casting issue certainly would make sense for a failure like that.

You're definutely lucky though that it stayed relatively intact! Thats a really good find too - Id bet most people wouldve pulled the head, saw the top was good, and just slapped it back together.

Glad you shared the pics, its definitely neat to see.

 

Yes I was definitely lucky. Currently I'm at the engine shop pulling the rest out and hopefully the builder ( my friend) will show me how to run the hone on all the cylinder's today before I leave.