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Old 07-06-2006, 11:15 PM   #1
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Default Burnt Exhaust valve, Why???

:(
I drove our SSEi Friday night over 120 miles with no problem, let my son use it Monday to go to work and he said he exited the highway after 4 miles and it had a terrible miss. Brought it home and I check for spark-ok, check for fuel injector pulse-ok, removed spark plug and found the ground electrode was half gone.

http://dougelam.com/sparkplug.htm

Check for compression, none. Removed cylinder head and found exhaust valve had a hole in it, No pic-already sent to machine shop. This Happened like real quick. Is there something I should look for to cause this???
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Old 07-06-2006, 11:22 PM   #2
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How many miles are on the car?
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Old 07-06-2006, 11:26 PM   #3
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120,000. AC-Delco plugs and wires at 75,000
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Old 07-06-2006, 11:28 PM   #4
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Did he put gas in it? If so, he may have put 87 in it? If he did, it'* possible that'* what did it.
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Old 07-06-2006, 11:37 PM   #5
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Here'* a decent site that includes a section about half way down the page on what causes valves to fail. In short, excess heat buildup in that cylinder. The cause for that heat buildup is the hard part. I've seen some plugs do that from too much knocking and the sound shatters the electrode. I'd think your knock sensors would prevent that, if operating properly. In theory, if he did put low octane gas in it, and then drove the crap out of it, it could cause excess knocking, and excess heat build up.

http://www.aa1car.com/library/ar1192.htm
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Old 07-07-2006, 12:25 AM   #6
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Here'* a link to an old post on pre-ignition. Have you been hearing any pinging?
http://www.bonnevilleclub.com/forum/...+plugs&start=0
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Old 07-07-2006, 12:32 AM   #7
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As stated above heat is what did it. Is the piston intact? Normally the piston will chip and that chiped part will get crumbled up and exhausted into the exhaust system (usually the cat). If it did chip part of that could have made a hole in the valve.

Chipped pistons are the result of running to lean and having to much detonation.
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Old 07-07-2006, 12:36 AM   #8
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Any modifications to the car? Specifically a supercharger pulley? Have you checked (or can you) the fuel pressure? Check the injector for that cylinder as well.
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Old 07-08-2006, 12:08 AM   #9
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I order of your responses;
He did not have to refuel. His mother left him a full tank of premium. She only uses speedway premium.

We never heard any spark knock. After removing cylinder heads, I found no signs of parts in cylinder.

www.dougelam.com/pistons.htm

No modifications, YET, I did remove the catalyst media from catalytic converter.
After I removed it the engine developed a miss in one cylinder for a couple of minutes. I revved it and it went away, till now. I think the end of the spark plug wedged between the exhaust valve and the seat, starting the burning process.

Received a call today from the machine shop, said head was cracked in that cylinder and one next to it. Found one for $70, will pick up and have valves ground with other head.

Is this when I change supercharger fluid???
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Old 07-08-2006, 11:22 AM   #10
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The supercharger oil is self contained in the blower snout. You can change it now or later but doesnt matter.
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