Power Valve Hitting Piston - 2009 M8T

[dirtsnow]

So i pulled my pistons to check everything and both pistons are damaged from what looks like the power valve. The damage lines up perfectly with the edges of the power valves. Has anyone else seen this issue? I've attached a picture

These are new pistons last year so i pulled the old ones out to check... and sure enough, they were damaged too in the exact same spot. I'm just going to shave a smidge off the valves with a file unless some has a better idea.

 

[skibreeze]

I had the same issue on my 08 Dragon, my guess was from excessive heat form one of my burndowns.

 

[samsquatch47]

Should be no reason to trim the guillotines, unless it's a big bore. This might sound stupid but, did you have them installed upside down?... They are cut at a specific shape and angle for a reason... I've seen lots of guys install them upside down. Even seen "mechanics" do it lol. Something to look into and an easy fix. Just an idea.
Cheers and good luck

 

[m8magicandmystery]

the 07 has a groove/slide so they only go one way so why did they change to be able to go either way..??..anyway is there stops that can be pounded out abit and that's why the slide is going a tad deeper..??

 

[dirtsnow]

They can only go in one way. There is a step at the top that won't let you bolt it in the wrong way. Could the stop on the cylinder be slightly worn down from 3500 miles of use thus allowing it to close a little further? I don't know how someone would put the power valves in backwards, the just can't go that way in my sled.

 

[Arctic Thunder]

They can only go in one way. There is a step at the top that won't let you bolt it in the wrong way. Could the stop on the cylinder be slightly worn down from 3500 miles of use thus allowing it to close a little further? I don't know how someone would put the power valves in backwards, the just can't go that way in my sled.

Yea, you can't put them in upside down just because of the way they are made. But you could be right with the wear on the stop on the valve or the contact point that it sits on. Might be a few thousandths wear on each letting it hit.

Stock cylinders?

Thunder

 

[dirtsnow]

Yes. Stock cylinders. Think I will just shave the valves a hare. They only hit on the ends and it's a pretty easy fix.

 

[HCR10]

I had a 07 turbo with high miles do the same thing and I found that it was a combination of the cylinder and power valves wearing out. I purchased new valves and found they almost cleared but it still hit. I clearanced the face of the valve and have no problems but I was told that it would not run the same if I clearanced the valve but it has ran spot on like nothing was changed. Maybe I got lucky but if I was you cut the valve and run it.

 

[samsquatch47]

Sorry didn't look at my M8 power valves that close. The old M7/F7 motors and the 1m 900's could be assembled with the valves either way. Guess we all learn on here lol.

 

[jim]

I have the same thing happen. not sure if it was from excessive carbon buildup or just clearance issues. Trimmed the powervalves back a bunch 1/8 an inch...still runs great turbo M8.