After making a 60 mile trip my 77 Aspen started running rough coming down Main Street. When I got home I pulled the plugs and found the electrode on the #2 plug bent over to the side and 1/4 of the insulator missing. So what happened?????? Both bolts on choke plate are still there.

A quick comp check showed 85 PSI compared to 105 on #3

If I have time I'm going to pull the valve cover off when I get home tonight.
Thanks In advance Mike[/img]

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Thanks Mike

Well, we know that your plug to piston clearance didn't suddenly change, so perhaps the insulator cracked, fell down into the cylinder and got mashed into the electrode.

I think I would install another plug, crank the engine over with the coil disconnected, and then remove the plug to see if it is undamaged.

- Mac

I cranked it over with out plug before I stuck my compression gauge in it. I put a new plug in it and cranked it over, then started it and ran it a couple minutes. The gap was the same as when installed.
I guess I will pull the head come spring and look at everything just for piece of mind. I would do it now but I'm headed back to work for 28 days.
Thanks Mike

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Thanks Mike

Autolite? Champion? What brand?

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

NGK's that have been in car for 10,000 miles at least.

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Thanks Mike

Some detonation/pinging may have cracked the porcelain.

Then it broke off, bounced around and bent the electrode.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

More than likely the detonation took the top of the piston land off