I have a fully built engine from laskey racing and a fully built head from combustion contraption cylinder heads. The engine has about 800 miles on it so far. Cyls 1 2 and 4 the spark plugs look perfect but the plug for number 3 always has a black insulator and will sometimes be slightly wet with oil after driving. compression numbers all check at 205, the motor has a 9:1 compression ratio.

Im hoping the problem is the valve seals.. How hard is it to change out the valve seals? I have dual valve springs in my head, would that make it any harder?

Is there anyway to test to see if the problem is with the rings or with the valve seals?

 

Do a leak down test, this will tell you if it is the rings, valves or head gasket.

 

Normally oil on the external part of the spark plug, the white insulator, is caused by a leaking spark plug tube gasket on the valve cover head.

But if you do have an engine issue then a leak down test is what is needed. You will hear air leaking in the intake manifold if it's an intake valve face or seat, the exhaust pipe if an exhaust valve face or seat leaks, and hear it coming out of the valve cover vent if it's a valve stem seal or piston rings.

Here's my compression and leak down how-to: http://robrobinette.com/S2000Compression.htm