TR6 High Compression in One Cylinder

[NutmegCT]

Martin - great to hear you're making progress.

I'd (eventually) also check the valves and valve adjustments, at least on the problem cylinder.

Congrats.
Tom M.

 

[Martin Secrest]

A fine idea.

 

[pdplot]

"Carbon On The Valves".
Walter Matthau in A New Leaf speaking about his Ferrari he can't afford to fix - unless he marries a rich girl.

 

[Martin Secrest]

Pulled the valve cover yesterday, all the gaps are still spot on. This has me leaning toward two possibilities I guess, that the carbon buildup on #1 was from the bad plug lead, or I have a bad oil ring. If it's the ring, can I replace that just by dropping the pan?

Meanwhile, the compression is still slowly dropping as I cycle Seafoam thru the cylinder, will check it again today, hoping it's down to 150lbs like the others. Getting close.

 

[NutmegCT]

You may be on to something regarding the bad plug lead. If there was frequent voltage disconnect while the engine was running, you could certainly have a buildup.

when you first pulled that plug, was there an oily buildup on the plug? or a thick carbon buildup on the plug?

I'd think that oily buildup would be due to piston ring; dry carbon buildup would be misfire.

 

[CJD]

Aren't you supposed to use seafoam while the engine is running? I always did, per the instructions, but maybe there are different types now, like everything else. I remember letting the engine suck it in, barrels of smoke coming out, and then no more carbon after, like, 10 minutes.

The manual specifies removing the head to de-carbon the cylinders on regular intervals, so carbon in the cylinders is a normal occurrence. It's the fact it is only in one cylinder that is the problem.

 

[Martin Secrest]

You are I suppose but I have so much apart right now - entire cooling system down, etc - I can only run it for short intervals. So as per Tom M's suggestion, I'm soaking and running it out. Seems to be working ...

 

[NutmegCT]

I actually learned about the "cylinder soak" from a tech advisor (Jim Davis?) at the Seafoam company itself. So far it's worked for me.

Many folks do run Seafoam directly into the carb while the engine is running. Also add to fuel.

Anyway, glad the compression is settling down.

Martin, when you first pulled that plug, was there an oily buildup on the plug? or a thick carbon buildup on the plug?

I'd think that oily buildup would be due to piston ring; dry carbon buildup would be misfire.

Tom M.

 

[CJD]

Dry carbon would still increase compression when oil is added to the cylinder. In other words, adding oil should always bump compression a bit...unless the oil the already there.