I have a ssb - cylynder not firing - #6. took out plugs and number 6 fouled. More worisome number 7 looks compressed - still firing with no damage to the porcelin and still has a gap. I replaced both and engine seems to be running great. What the **** happened to number 7????. Does the engine need to come apart??? Timing is good and no audible detonation. All othr plugs look great.

I had a 454 Magnum that come from the factory with a hard start situation. Turned out a few plugs were not gapped and there was practically no space to get even the smallest feeler in. Regapped and worked fine for many years to come. A service bulletin was put out and that's how the mechanic knew what to look for or else it would have taken for ever to figure out.

I would do a compression and leak down test and go from there. You could also buy or borrow a bore scope and look in to the cylinder through the spark plug hole. The bore scope is a really neat tool to look in areas you can not see without tear down. You may be OK but I would want to do some checking.

What would push the electorde down w/o cracking the porcelin or showing visible damage to the metal on the plug. Odd that the whole thing was not smashed together if piston hit the thing?? I will check the compression tomorrow.