What does it mean when I pull out my spark plugs and the rear half of the threads (away from the electrode) are covered with oil? I also have a small puddle of oil on the pass side of the intake manifold coming from the manifold bolt by cylinder #4. ???

Thanks, JR

Have you checked your valve cover gasket on that head for oil leaks? Sounds as though your valve cover is leaking and the oil is seeping down along the head and around the plug. I've seen that many times.

I have the same oil on the threads of my plugs and I definitely don't have a valve cover gasket leak. I hope someone can help us understand what's causing it.

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It’s a BIGger BLOCK!

Nope, no oil leaks anywhere. Valve cover gaskets are good. I'm wondering if it could be valve stem seals, but I don't know why the threads would be covered. Any clues as to the smal puddle of oil on the intake manifold from the bolt?? The engine has a breather on the pass side valve cover and a PCV on the driver side.
Thanks,
Jim

You'll find that the oil on intake is seeping around the intake bolt threads. Usually the two in the middle. Just take them out 1 at a time and put some permatex on the threads. Re-torque to specks.I just fixed this on my suburban. I never did understand how the spark plug threads get oily. I've seen it on many vehicles though. Maybe it's unburned oil from the cylinder that got by valve guide seals?

I know this is going to contradict some of what was said before but I had a similar issue on my 67 Big block two years ago. I had valve cover leaks so I decided to replace the covers (chrome on covers bad)and the gaskets when I did my tune up (new plugs points etc.) 1 year later I had to remove the plugs to manually turn the engine over while replacing and setting my lifters. Lo and behold...no oil on the threads (actually the plugs looked like perfect burn for about 1500 miles). I attributed this (no oil on threads) to the new covers and gaskets and no oil leaking anymore. This has been my experience even though you say you don't have any oil leaks there.

Mytmouse