Plug Problem (pic)...
 

I just found this three hours ago during a plug swap. It's an autolite 3924 and I am putting in platinum 3924's as part of a regular 4000 mile tune-up.

None of my other plugs exhibited this. I have been losing a little oil (say, a quart over a months time) and this plug has been a little "oily" before. I have only about 12000 miles on this new motor. This was plug number 5. I had no problems at all. I have a feeling this is no bueno...

Valve seal or blow by the rings

compression check....
 

Correct me if I am wrong but a comp check won't really specify the problem.
Once I verify a serious compression problem, I guess I will have to pull the head.
Joy.

A compression check will identify whether it's the rings or the head, if you do it dry, then wet. Do a normal comp check in that cylinder, then add a few squirts of oil from an oil can into the spark plug hole, and check the compression again. If the numbers go up significantly, you have a ring problem. If they don't, it's the head. A leak down test will then specify where in the head the problem is.

Take care,
~Chris

Thanks pkrwud...
 

I am only allowed +/- 20 PSI difference, correct? (dry)
I'll post the compression results...

no more than 10% difference from the highest reading to the lowest, but that's from all the cylinders. You just need to do #5.

PSI guesstimate...
 

PKRWUD,
This is the first test I have done with TRW flattop pistons and a .030" overbore. I am guessing my compression is about 9.5. Do you have a ballpark PSI figure? I am going to check the entire left bank of cylinders.
I have been "losing" a little oil over the last few months and a little coolant but I never could find evidence during an oil change or coolant flush. Just this number 5 cylinder plug always being a little oily.
I have a feeling when I dyno'ed 258 rwhp before the blower, which was about 30 hp low for my combo 6 months ago that I had the beginnings of a head gasket problem.
What is surprising is that it is relatively subtle. Very slow leaks but I think this has finally done it...
and I just put new headers and plugs on yesterday...Murphy's Law...

the numbers could be anywhere from 130 to 170, and be fine. It's the difference between the cylinders that counts. Remember to warm up the engine first, and to block open the throttle while doing the tests.

Take care,
~Chris

results...
 

All 4 were within 10 psi of each other
#5 115 PSI average of 3 (all with about 3 cranks on the starter)
#6 120 PSI " " "
#7 115 PSI " " "
checking 8 now...
...engine reasonably warm, i.e. 150 degrees, 65' outside

I have a feeling it might be a bad valve seat or bad guide which, I just learned from a friend is not uncommon on Trick Flow TW heads...

If 8 comes up same, I am pulling the upper intake and valve cover and inspecting the #5 valve seal with a flashlight.

Let me know if this makes any sense to you.

Either way, the head has to come off.

Thanks for your advice.

Valve seal...
 

I am trying to peer down the springs on number #5. It's harder than heck to see down there and see if the seal isn't seated properly.
I have never seen one not sealed so I really don't know what I am looking for, but there is nothing obvious right now...Having a beer before I go and have another look see.

here it is...
 

not the best pic, but I don't see anything awry in there...
So if compression is good, and there doesn't appear to be a seal problem..then??
I am waiting to pull the head to make sure I think of everything first, or at least try...

Valve guide?
 

My best guess now is a bad guide. So much for bronze guides...

sounds right to me.