MG Car Repair: 1973 MGB-GT Cylinder Head, crank case, wet test

Question
Hi,
I recently bought a 73 GT. The pressure test showed 130 lbs across all 4 cylinders. However, the engine still burns a bit of oil. Would the fault likely lie in the valve stem guides and seals?

Thanks,
Dale

Answer
Hi Dale,
130 PSI across all cylinders is very rare. Most all engines have some variation between cylinders. Was the compression test run with the throttle open?

You can not test oil rings with a compression test unless you run a "Dry" test and then a "Wet" test.
The first "Dry" test is done with all plugs out and throttle open, then put several squirts or engine oil in that plug hole (about a teaspoon of oil) and run another compression test on that cylinder (throttle open) do every cylinder that way. The "Wet" test will be higher than the "Dry" test but should not be more than 10 to 15 higher. If the "Wet" test is much higher than the "Dry" test, then you have a ring problem.

A symptom of a ring problem is blue smoke from the tail pipe on hard acceleration as viewed from behind the car and especially noticed when speed shifting.

A symptom of valve guide problems is blue smoke out the tail pipe when first starting up but little to none noted after it is running. The only valve stem seal that MGs have is a "O" ring just below the collar to prevent oil puddling from running down the stem.

Don't forget to look at the oil to see that it is not too thin due to gas contamination or too thin weight oil was installed.

Also check to see that the crank case venting is correct and not clogged up.

Howard