[Mgs] MGA crankcase ventilation

Stan Fickes spridget at gmail.com
Sat Jul 13 13:22:17 MDT 2019

I have an MGA 1600, under 2,000 miles since the engine rebuild. While
working on an unrelated issue, I discovered that the front air filter was
thoroughly soaked in oil. The source was the vent hose between the air
filter and the valve cover. I found significant (to my lack of experience
with this system!) pulsing air blowing through the hose at idle.

A compression test returned values between 125 and 130 psi in each
cylinder. I used my blow-down tool (air fitting brazed to spark plug casing
-- http://mgaguru.com/mgtech/engine/be110.htm -- thanks Barney!) and heard
no hissing on any cylinder; valve cover, carburetor, or exhaust.

Then, with all the plugs out, I cranked the motor with the starter and felt
plenty of air pumping out of the valve cover port. I think that rules out
poor ring sealing since there was no compression.

Any ideas where the pulsing air could be coming from? The bottoms of the
pistons oppose each other, so there should be no net air movement from
there. I doubt the volume of air coming out the hose is normal, but I am
certain the volume of oil is not. It was dripping from the filter element.
If the air is normal, I suppose I could make a baffle to reduce the
splashed oil into the hose, but I shouldn't need to change from what the
factory made.

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