MG Car Repair: Oil leak with Weber DVG, excessive blowby, fuel air mixture

Question
Hi Howard,

I recently purchased a 1978 MG Midget.  When I took it for a test drive, the car started leaking oil from what looked like the base of the dipstick tube.  The now PO took a metal rod to the dipstick tube and gave it a couple thwaps with a hammer, which seemed to solve the problem.  I bought the car and drove it home, about a 4 hour trip, with no issues.

Now the leak has returned.  After researching on the internets, I found that the car has had the Weber downdraft conversion, but the crankcase was just vented to atmosphere.  So I bought and installed the air filter for it and ran a hose from the valve cover to the base of the air filter.  However, this did not solve the leak.  Additionally, now the car jerks at low throttle.

It appears I will need to do a compression test.  Is there anything else I should be checking?  Is it possible that the dipstick tube comes loose periodically on these cars?

Also, now that I have the blowby gasses routed to the carb, do I need to adjust the fuel/air mixture?

Thanks in advance,

Brian

Answer
Hi Brian,
A dry and then a wet compression test is needed to determine the ring condition. Or if you have access to a leak down tester that will tell also.

Excessive blowby is the normal cause of oil leaks at the dipstick. Dipstick tubes do not normally come loose. Venting to a air cleaner should have been enough to correct the problem.

Run a dry compression test (throttle open) and write down the results and add 3 or 4 squirts from an oil squirt gun or put about a tablespoon of oil in the plug hole after the dry test and run it again wet and write down the results. The wet test will always be higher but should not exceed it by more than 10% to 15% higher.

Howard