Originally Posted by rmdhawaii (Post 6937377)

First, thanks everyone for your helpful comments.

This is the second piston/sleeve for this engine. I did a WOT break-in and it ran good for 8 months with no problems. The pinch is still really good. This is my number 3 engine that runs in whatever third car I'm running - so MTX-4 and then NT1. Like I said before, the engine was running good, no problems, so I didn't have a reason to take it apart. Most of my time was spent working on my other two engines.

I took this engine apart at about 11:30pm and I still had to work on my other engine, so I missed some tell tale signs on the piston sleeve that would have given me a better idea of what happened. You know how it is - if you don't know what you're looking for, it's easy to miss things. You guys really helped me pin point the problem.

As you can see from the photos below, a part of the piston clip broke off. See the other gouge going toward the top of the piston? And the pin created a bur on the intake port. Then it looks like it it got caught on one of the other intake ports as the piston was going up, which resulted in the gouge you see on the side of the piston. Rest of the engine looks fine, well - except the button head which I've known about for a while - ha ha, but that's just me being lazy about doing something about it.

I wonder how long this has been here. Maybe months - maybe it happened more recently. Hard to say.

Thanks again. I always appreciative the help I get from the smart guys who hang out here. Enjoy the photos.

http://nitrokb.netne.net/images/tz piston 04.jpg

http://nitrokb.netne.net/images/tz piston 05.jpg

http://nitrokb.netne.net/images/tz piston 06.jpg

http://nitrokb.netne.net/images/tz piston 07.jpg

http://nitrokb.netne.net/images/tz piston 08.jpg

Originally Posted by Riketsu (Post 6974270)

My suggestion is, throw away your Piston/Sleeve and get a new one. I prefer spending a few bucks than getting headaches on race day.