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Valves hitting piston

Old 07-21-2010, 06:27 PM
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Valves hitting piston

I need some advice, new to the forum and have owned my Hawk with pride for just over a year, I love this machine, but have had a CCT failure. My question is, should i be overly concerned about valves hitting piston? There were no deep marks, just a very light outline of 2 valves hitting the piston. I have a slight divot in top of piston. Should I tear it down???? Don't have the cash to do so, my mechanic says the SH is built like a tank and I should be ok.
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Old 07-21-2010, 06:28 PM
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I would definately pull it down to inspect the valves.
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Old 07-21-2010, 06:35 PM
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Have you done a leak down or compression test? How does it run?
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Old 07-21-2010, 06:35 PM
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Sorry I meant to say that I am going to replace all 4 valves, I am worried about the stress on the piston
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Old 07-21-2010, 06:36 PM
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No compression test yet, pulled heads off. Need to replace all 4 valves and both CCT, the I will do a compression test.
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Old 07-21-2010, 07:10 PM
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Unless you have a good sized gouge in the head of the piston, you're probably okay just replacing the valves. The valve stems will bend much easier than a connecting rod. You might want to carefully smooth out the "outline" of the valves on the piston head a little though. A sharp edge on the piston could cause a hot spot, leading to pre ignition.

Hope you get it back on the road soon.
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Old 07-21-2010, 07:12 PM
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This may be a stupid question, but what would quantify a gouge????????
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Old 07-21-2010, 07:51 PM
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That's a very subjective question. Can you post pics?

Most of my experience is with cars, and the usual repair is to do the cylinder head, smooth out any marks on the piston head, then put it back together.

I did suck a valve in my '69 VW while doing 65 mph on the freeway back in '73 though. The valve head went right through #3 piston. Destroyed the entire engine.
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Old 07-22-2010, 04:03 AM
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Originally Posted by dbog44 View Post

There were no deep marks, just a very light outline of 2 valves hitting the piston. I have a slight divot in top of piston. Should I tear it down???? Don't have the cash to do so, my mechanic says the SH is built like a tank and I should be ok.

If you just bent the valves, don't sweat the piston.
If you broke a valve, definitely tear down time.

Out of curiosity, what RPMs were you turning when it popped?


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Old 07-25-2010, 05:58 PM
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Thanks for all of the help guys.

I was turning about 5500 rpm's when the cct broke loose, but I was on my way to full acceleration.
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