What caused this ?!?

**AndyP** · 25 March 2010, 13:01

Looks like the chrome has come off the ring and that knife edge on the valve pocket should have been removed at manufacturing as it's a known problem that it can melt.
What sort of pistons & rings are they?

**Jamo** · 25 March 2010, 13:16

Are they custom pistons? If they are then the valve pocket need to be machined down as those cause hotspots causing the piston to melt.

See http://www.s2forum.com/forum/showthread.php?t=5523

I had mine machined down by JE just like that thread so it would not occur

**TDHAA** · 25 March 2010, 13:18

They are the Mahle IMSA pistons.

Attached Files

imsa piston.jpg (24.4 KB, 84 views)

**TDHAA** · 25 March 2010, 14:04

Originally posted by Jamo

Are they custom pistons? If they are then the valve pocket need to be machined down as those cause hotspots causing the piston to melt.

See http://www.s2forum.com/forum/showthread.php?t=5523

I had mine machined down by JE just like that thread so it would not occur

Thanks man,the thread figured it out for me.

I will send them back hoping they can be saved.

Still questionmarks with the ringproblem/bearingfailure though..

I hope you'll get your S2 running again soon

**GT500** · 25 March 2010, 14:30

Sounds like you got oil surge under braking!

More oil and baffles needed!

**caterpillar** · 25 March 2010, 14:55

you may have the ignition /coil problem... then you have some detonations/ then you get bearingsproblem, then pistonsproblem... then you have the gone engine...
if you arent sure/ change the ignitionsparts, all of them

**repo** · 25 March 2010, 15:16

Looks like detonation to me. It can cause all these issues, melting, chrome chipping, bearing problem.

**90/90qs** · 25 March 2010, 16:56

did that piston in shot 4 hit the oil squirter?

**SteveH** · 25 March 2010, 17:38

If you use the wrong rings on a forced motor I've heard of issues with the chrome surface detatching. Detonation would most certainly assist this process.