Triumph Repair: Bore Wash - Worn Rings, oil leaks, compression gauge

Question
QUESTION: Hi Howard,

I have a 1966 TR4A.  It has about 7,000 miles on a rebuilt motor. At the beginning of last season I suddenly started experiencing severe oil leaks.  I checked the usual suspects and thought I had it solved when I fully serviced the PCV.  Now I am suspecting excess crankcase pressurization caused by worn rings. The reason for my suspicion is, after 2,500 miles of running, I traced a “hot-start” problem down to an overly rich carb mixture thanks to an under-qualified mechanic. As additional detail, the car started fine cold and ran great.  It was just a hot-start issue caused by the rich mixture.

So, I have heard about a rich mixture causing bore wash and destroying the rings.  Based on the above info, do you feel this is likely, unlikely, or simply cannot tell?  I didn’t think the mixture was too rich but...?

Curiously, the oil leaks began almost immediately after the carb mixture was brought back in tune.  Is that related or purely coincidence? Plus, now that the carbs are in tune, the engine absolutely "sings" and, other than the oil leaks, runs perfectly in every other way.

I understand the best tests for this are dry/wet compression tests and a leak down test. What values should I look for on a compression test?  If I decide on a leak down test, I would take it to a qualified shop since I do not have a compressor.

Thanks for your help.

Bob


ANSWER: Hi Bob,
You can do the Dry and Wet compression test with any inexpensive compression gauge and use that to decide to look for a shop with a leak down tester.

Run the dry compression test first and you should see from 135 to 180 PSI with only a small difference between cylinders. Be sure to hold the throttle open and turn the engine at least 4 or 5 revolutions on each cylinder test.

The wet test is done by squirting about a teaspoon of engine oil in the plug hole and do the same compression test on each cylinder and the readings will be higher but should not be more than 10 to 15 higher. If the wet tests are much higher, then it is a good indication of a ring problem.

At this point before tearing the engine down you should call shops to find a shop that has a leak down tester, Preferably a shop that does work on British cars.

There are many reasons for ring problems besides excess fuel which is the least likely from my experience. The cause I seen the most was detonation which burned down the edge of the top of the piston directly opposite the spark plug. Which caused the rings to stick deep into the ring groves and start to burn the piston lands.  
Howard

---------- FOLLOW-UP ----------

QUESTION: Hi Howard,

I ran the dry compression test but, did not have time to run the wet test since I was dropping the differential tonight.

However, the results look excellent which leads me to believe the piston rings are in great shape and doing a wet compression test would be unnecessary. The readings were 175/ 172/ 165/ 175psi.  What do you think?

Back to my reason for all this was oil leaks everywhere apparently from crankcase pressurization.  So I went back to my PCV valve.  I noticed the valve in the metal base was sticking closed ever so slightly.  Probably enough to allow crankcase pressure to build sufficiently such that when the valve opened, it probably slammed closed in the opposite direction (intended behavior to avoid excess vacuum into the intake).  So after cleaning it out (again!), ideally, it will now open easily and gradually to manage crankcase pressure before it becomes excessive.  Do this sound correct?   

Let me know if you think I should still perform a wet compression test.

Thanks

Bob

Answer
Bob, Did you try to tighten all of the bolts where you have oil leaks? Also you did not say anything about burning oil?? Excess crankcase pressure will ALWAYS cause burning of oil (blue smoke out of the tail pipe) You could be racing down the wrong road if you have no signs of oil burning and only oil leakage.
Howard