As many of you might have seen I have had some posts talking about blowing cats. I ruled the problem to fuel entering the exhaust, now I am not so sure. I decided to change my spark plugs today and boom what was this. All over the threads of 7 of 8 plugs was a ton of what appeared to be oil. There also appeared to be a little bit on the resistors (I can't remember if this is the right term. I am talking about the part where the spark actually takes place) too. Now for the slightly strange part. I don't know how to describe this but I will do my best. If you were looking at the top of the spark plug where it is inside the motor, there obviously a circle that goes around, basically the end of the threads. Now only one or two of these is totally covered black, most of them are only precisely half. Now here is my question. I see a few reasons for this oil. Could I have a blown head gasket and oil is seaping past somewhere? Could it be from blow by on the rings? Or could it somehow be coming down from the valvetrain? The later seems possible to me because it would seem that the problem is happened on one side, meaning either intake or exhaust. Does this sound like a possibility? I am a bit strapped for cash right now so to take it to a shop and let them pull the motor and start looking inside is going to cost a lot! If it's on top then I could either repair the heads or just put new ones on. They are stock BTW. Is there any way for me to really know whether it is on top or on the bottom side? I'd really appreciate any help, and if you would like to see a picture of the plugs to understand what I mean, please just email and I will try and send one. I really want to get this car running well, cause it used to be really quick, and now it's just sitting there, and this oil all over the threads is bothering me. I'd really appreciate whatever help or advice anyone can give. Thanks very much in advance.

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87 GTA 350 L98
K&N filters, beefed up TH-700r4, Accel Manifold, Ported Plenum and Runners, Fuel Press. Regulator 49.5psi, air foil, modified MAF, SLP cold air box, Hypertech Thermomaster chip w/160 thermostat, MSD 6AL and Blaster 3, B&M shift kit & megashifter, Moser Ford 9in Rear with Richmond 3.50 and locker, Edlebrock TES headers and Cat Back,Hotchkis setup in rear, Poly suspension and Koni in the front, relocated MAT, bypassed IAC, 300 lbs lighter

Fastest ET's
Stock-0-60 6.8, 1/4 15.0 @ 94
Best-0-60 4.7, 1/4 12.8 @ 112
Norm-0-60 5.2, 1/4 13.2 @ 108

 

oil can get in by the valve seals, the piston rings, the PCV, or from an intake manifold leak.

with 7 out of 8 plugs oily, my first guess would be the valve seals/guides.