951, head pulled off finally to find a chipped piston

[cptnyehy0]

I finally got around to pulling the 951 head off and getting ready to put the spare head on. When I pulled the old head off I saw that the first cylinder piston has a small fingernail sized chip / dent in it from where the valve came in to contact with it. Does this need to be replaced or can I get away with using it? Im expecting the worst. I can shoot some pics when I get home this evening.

Greg

[cmartin]

Is the damage from a prior incident or the reason why you are in there? If just a kiss, let it ride. What's the valve look like?

[smdubovsky]

Check the valve. If bent, even ever so slightly, it won't seal on the seat. Can use bright light, liquid, air pressure, etc to check (often in combination.) Can even try to relap the valve to the seat and look at the pattern.

[cptnyehy0]

Yes, the reason i am taking the head off is because I bent a valve. I have a replacement head with good valvles in it, so I just wanted to be sure nothing catastrophic would happen due to the chip in the piston. ill shoot a pic tonight, didnt get home til 10 last evening and went right to bed.

[jerome951]

Is it a dent from the valve edge (i.e. smooth indentation) or an actual chip (meaning piston material has come off)? If just a dent, it should be OK to re-use, but I wouldn't use a chipped piston.

[cptnyehy0]

yes it is a dent from the valve edge, it seems to only be on cylinder 1 and not 4. it looks like it has just been marred, not like a piece cracked out of it or anything like that.

[Vicegrip]

Depending on the hit I would check for a bent rod.

[Marc A]

FWIW, I had two valve hitting piston occasions when my 951 was turbo powered, one of which left a large smiley on the piston. On both pistons I used emery paper to smooth the edge of the indent while the shop vac was sucking next to the "smiley" There were no ill effects caused by the dent or repair.

While I agree with Kurt 99.99% of the time, the valves head will bend into submission before a rod is damaged as will the piston head.

I do agree with Jerome about the chip vs indent.

Marc

[SRG]

Having a small dent or dents on the top of the piston won't hurt a thing. Bent other stuff might. The texture of the piston top could effect intake/exhaust if it was heavy texture. Lots of pistons have recesses in them and I think some have experimented w/ more general textures on the piston top.

I once ran a 400 KTM single cyl. (4 stroke) motorcycle whose piston's top was covered in a bunch of small dents from a broken piston ring bouncing around. We fixed/replaced/rebuilt what was required but reused the otherwise undamaged piston - new ones were $$.The bike ran great - we used to joke that it was faster w/ our "trick" piston!

SRG