I took the heads off today and pulled out all my plugs. One of them, looks like it barely getting a spark and firing. I'd say 75% of the plug looks white as can be, and a small section on the backside is a little dark.

It's an Accel HEI non cc distributor about 2 yrs old, and about 12k miles on it.

The plug wires have about 200 miles on them.

Any ideas on this?

Also, the passenger side plugs all had oil down around the threads, what does this mean?

 

The oil on the plug threads is probabily from the passenger side valve cover leaking, or you spilt some oil will filling through the valve cover.
Wouldn't worry much about the one plug color as long as the combustion chambers all look about the same.
Could have been a minor vacuum leak causing that one cylinder
to run a little leaner.

If one chamber is clean as a whistle, you had a head gasket leak.
(Water)

Now that you have the heads off, measure the piston deck height. Bring the crank around to TDC. Using a straight edge across the deck, measure the depth down the bore of the highest point of a piston.

Then measure the diameter and depth of the dish.

 

I'm a bit confused, like I mentioned in another post a few mins ago, I have 4 grooved areas on my pistons, not one big dish???? sorry this is the first time I've taken heads off and actually seen pistons.

 

The "grooves are called valve reliefs. Not important right now.

Trying to id which pistons you have by the depression (dish)
volume and the deck height ( depth of the highest part of the piston to the top of the block at TDC.
Then you can calculate your true compression ratio and make an informed choice on cylinder head to get a cr ya want.

 

K, but about the plug and oil. I don't see it happening from an oil leak from the valve covers. Cause it was on the threaded part that is in the head.

 

Just trust me on this one .... I could waste a lot of bandwidth typeing a whole explaination on how the oil got there but....

It is unlikely to have come from inside the motor or you would have been complaining about blue exhaust smoke.
It more than likely got dripped down there and soaked down into the plug threads..... not to worry.....

 

Oh ok, I just wanted to check and make sure. I wasn't sure if you knew what I meant at first.

 

your plug should be light tan if your engine is running right. if it wasn't firing it would have been covered in fuel when you pulled it and you would have had a noticeable miss. white *might* mean the plug's a tad hot but if the rest of your plugs were tan then you should be ok. did it look like any part of the plug melted or bubbled? if you're going to raise compression with new heads you should start out with cold plugs and then if they foul out put in a set that's a range hotter until they stay tan. a rule of thumb is go a range colder for every full point of compression increase. you may also need a colder plug if you run a lot of advance, which increases temperatures.

 

Is the oil just on the threads or on the electrode itself? I had oil on plugs 1,3,and 7 and it was caused by a blown intake gasket on the lifter valley side. My car never smoked either, and there was enough oil for it to leak out onto the exhaust manifold. Just my experience.

 

just the threads.

 

Mark, have you ever heard of capillary action?? Look it up. This is how the oil got into the threads. Fbird was right. The reason you plug is clean is because you had water in that cylinder (head gasket). That would also explain the clean combustion chamber on the pic of your head. Was plug pulled from that cylinder???