Can You Run A Cylinder Head That Has Some Pitting?!? - Snowmobile Forum: Your #1 Snowmobile Forum
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Old 11-18-2009, 08:40 AM   #1 (permalink)
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Can You Run A Cylinder Head That Has Some Pitting?!?

My 1996 Mach Z 780 needed a top-end rebuild. When I took off the cylinder head, I noticed that the middle combustion chamber has some pitting and also what looked like melted piston on it. The sealing surface is clean obviously with no markings.

I took out the Dremel and lightly sanded down the imperfections and now only have some pitting. It came out really nice and is smooth to the touch, but will this not work?

I dont care if I loose a little performace, I just want to make sure its safe for the engine, and will run right.

Thanks,
Matthew
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Old 11-18-2009, 08:59 AM   #2 (permalink)
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mine has some light pitting also, from a piston coming apart. It runs fine. no issues at all.
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Old 11-18-2009, 09:02 AM   #3 (permalink)
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yeah mine was like that on my 400, still running strong, just open it every once in awhile to check it out.
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Old 11-18-2009, 11:37 AM   #4 (permalink)
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Chuck it up in a lathe on the spark plug and turn the pits out with sand paper!
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Old 11-18-2009, 01:56 PM   #5 (permalink)
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Yeah tha'ts what I did, made it nice and smooth. I didn't know if it had to be perfectly flat due to the combustion in that area.

But its sweet to know people are running pitted just as I will be!

I did see that they were cheap on ebay, but I have so much into this overhaul right now I just want it over with.

Thanks!
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Old 11-18-2009, 08:23 PM   #6 (permalink)
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The problem is the pitts will cause hot spots and preignition and running it long enough it will melt down!!!!
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Old 11-18-2009, 08:47 PM   #7 (permalink)
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If the pits are very small, it should be OK.
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Old 11-19-2009, 10:34 AM   #8 (permalink)
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Yeah the pits are small, there are many of them but I would say the largest one is no bigger than half the size of a pen tip.
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Old 11-19-2009, 10:42 PM   #9 (permalink)
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ive seen the heads get pretty dinged up from a ring breaking apart and hammering the crap out of it. the only problem with sanding it smooth is that it will change the compression ratio slightly in the one cylinder then it will not be even. i have put multiple motors back together with dinged up heads and not one of them has had a problem
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Old 11-20-2009, 08:20 PM   #10 (permalink)
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It'll be fine.Make sure there are no fragmented pieces that will come off.
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Old 11-21-2009, 09:06 AM   #11 (permalink)
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Yeah I'm starting to get the consensus that it will be alright to run. Seems like a pretty common thing. Thanks for the input guys!
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Old 11-23-2009, 01:08 AM   #12 (permalink)
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i have some pitting on one piston also, and I think something metal did it :-( not a ton of damage, but even the slight pits can be a prob? not sure what did the pitting, the rings were intact. here's my story: http://www.snowmobileforum.com/engin...case-hill.html
i'd love some advice, and i'll pay $50 an hour to whomever can help me fix this!
thanks!
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Old 11-23-2009, 09:37 AM   #13 (permalink)
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^^^^^^^^^^^^^^^^^^
Smooth it off the best that you can and run it, unless there are real big dings, then replace piston.
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Old 11-23-2009, 02:29 PM   #14 (permalink)
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nothing too deep

the small pits are definitely from something metal, my guess is a bearing part but not sure which and i can prob sand/dremel the imperfections but need to find out what broke off and did the damage, right? ... i've never opened a bottom case before, or the crank. any suggestions? thx
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Old 11-23-2009, 04:02 PM   #15 (permalink)
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Definitely should check it out, could be wrist pin bearing came apart, or crank bearing.
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