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TR6 Spark Plug - oil fouling '73 TR6

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backroadsjeff

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anyone have an opinion regarding the cause of oil fouling of #4 cylinder - Rings or valves?

This is the only cylinder that seems to have problems burning oil - I can go maybe 50 miles before the plug becomes so fouled it doesn't fire any longer.
 
if blue smoke comes out the exhaust at start up only its the valves and ifs it burns oil, smokes all the time its the rings, I would think that if your fouling a plug after 50 miles your rings are shot, put a hotter plug in that cylinder, my 2 cents
 
Years ago I had the same problem in my '73 TR6 powered TVR. The oil control rings were stuck in the piston groove. It was like the rings were in the same position as when a ring compressor is holding them in so you can install the piston. I don't know if the engine had been rebuilt by a PO or not. I overhauled the engine and fixed the problem.
How many miles are on your engine?
 
If you go to the local auto parts store, you can find little sleeves that screw into the spark plug hole, and the plug screws into the sleeve. It protects the plug from oil fouling. If it is just one cylinder, this a great way to ride it out until you actually address the problem with tearing into the engine. (I've known people to use these for thousands and thousands of trouble-free miles.)
 
Check the compression wet vs dry on all cylinders to see if it's a ring problem.
Chances are you've got a broken/stuck oil control ring in there.
You can do it "engine in" by removing the sump pan and the cylinder head but it's a fair bit of work.
Once you're in there you'll likely end up changing the rod bearings, main bearings and thrust bearings not to mention a new ring set. Don't ask me how I know this /ubbthreads/images/graemlins/shocked.gif
 
Thanks to all for the advice and suggestions! The car has in excess of 95k miles and I don't think the POs had done any engine rebuild. My plan is to pull the head, check/rebuild the head as necessary then check the piston rings. I hope the cylinder itself isn't damaged because I'm not up for pulling the block out at this time....

Jeff
 
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