To follow up on a post I made that JE pistons (at least the 11:1's for the Raptor) are garbage.

Pictures

 

Damn...that does'nt look good. after how much use? and what type of fuel?

 

I guess I should have stated these things even though they've been covered in other posts.

1st Piston about 4 weekends and two weeks in LS Utah/St Anthonys Idaho and Montana. 170/175 Dyno jets and 91 octane and sometimes Ultimate 4 (once).

2nd Piston. Upped the jets to 190/195 dyno jets, replaced needle valve assemblies with BSR42 assemblies to flow more fuel. Never used less than 95 octane and never more than 100 octane. Lasted from September 2003 till April 2004. 10 plus weekends and or extended weekends worth of Dune and desert riding.

Several people have had this problem with these 11:1 pistons. I upped the jetting and octane incase detonation could have caused this. I'm not running lean and detonation isn't the problem. JE has apparently changed things in this line of piston to combat this. Couldn't say if I had the updated version or not.

 

That makes me feel good that I took my 11.1 JE out. I'm still running JE but its higher comp. with a little more meat on top so I hope It dont let go on me. Sorry about the problems you've had and hope you get things straight. Slim

 

A friend 1BadRaptor is going to a Ross 13:5:1 and has offered me his 12:1 JE. I'm probably going to take it, it's a good deal. I haven't heard of the 12:1's having this problem. Keeping fingers crossed.

 

is the JE 10.75/1 the same as the 11/1? please tell me it's not.

 

Yes, sorry. We just call it an 11:1.

This is the 102mm bore not the 100mm bore though.

 

Yeah' it is the same; most of the time they are refered to as a 11.1. JE's are usually higher in actual comp. than listed from the factory. Its obvious there is problems with some JE's but I ran my 11.1 JE for well over a year witout any problems even before they made the changes to the wrist pin area. My 11.1 was the first style JE's so its hard to say wether all 11.1's are prone to having the same problems; could have been a big bad batch that went out from JE. It will be up to you on wether or not to change it out or take a chance; hard call. Slim

 

That is a picture of "classic detonation" Everything about this says detonation. See the errosion around the hole? That screams detonation!!!
The only thing I don't understand it why? Only 11 to 1 and you should be able to get by with pump gas, but you say you ran 100 oct?
Can you get a real closeup of the plug that came out of this thing? Head too? By the way; nice clear pictures!!!

 

If I had not seen the pictures detonation would have been my first instinct and it still does look like detonation in a lot of ways. The thing that stands out to me is were the cracking looks like it started at. Look along the bottom of the wrist pin holders; it looks to me as if both pistons started cracking there at the same places same side and spread outward toward the middle of the piston and eventually the end result is it started comming apart. This is a tough one to call.