I read somewhere, that 4-stroking it isn't such a good idea. What engines? What temps were you running? Did you let the engine warm up first or did you go straight to WOT?

I'm basically doing a rebuilt OS .12 TZ 3-port (piston, sleeve, rod & rear bearing replaced; front bearing replace earlier) and a NIB .12 Sirio STI. The TZ took a lot of abuse, as it was my first engine. I did the "idle 3 tanks and then putt around the track for 3 more tanks" break-in method. It was a good engine to get started with. I tried a lot of different things and learned a lot in the process. I don't think it even saw 10 liters before the piston started getting loose. We'll see how it does this time around.

Here is an article I found on heat cycling, if anyone is interested:
http://www.rcuniverse.com/magazine/a...article_id=397