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MG MGA - MGA crancase vent smoke/oil consumption

I have 1600 MGA with crossflow cylinder head. Am using a lot of oil; down to 1 litre in 100 miles. Also there seems to be smoke from the crankcase vent tube. Initially I found oil drips onto exhaust causing smoke,thought some coming from from rear tappet cover. Hard to stop but looks OK now. Am still getting oil leak under front of engine which could be partly coming also from front tappet cover which will have another go at. I do not think I have smoke from actual exhaust tailpipe. Have checked compressions which were 175 psi (12.5 kg/cm) on 1,3 and 4 cyls, and 180 (13 kg/cm) on 2. Plugs on sooty side but not excessive. Am going on a trip to Angouleme in France in about a month which probably will cover 5/600 miles. If I have to I will carry 10 litres of oil, but don't want be silly.
What thoughts people?
H L Davy

Thats a lot.
Try running engine with clean paper underneath, to see if its a leak.
Also check the rad for oil in water
Do you have valve stem seals on the intakes?
Any ble smoke on the overrun?

Art Pearse

No oil in coolant and no loss of coolant at all. No emulsion on filler cap. Oil pressure 60 hot. Engine temp 90C. In fact runs beautifully. No blue smoke that I can see. Dont know what seals there may be on valves. (thought valve stems always have seals?)
H L Davy

The usual MGA stem seals just fit under the collets, stopping oil from the spring cap running down. They don't seal the stem.
Art Pearse

Front cover oil seal, rear crank leak?

Colin Manley

Of course the rear seal is only the imperfect reverse scroll but if oil was going her it would be coming out by the cotter pin in the bottom of gearbox bell housing, this quantity would be obvious.

Paul Dean

I had a similar situation some years ago when the tappet cover gasket was leaking lost a lot of oil on a long run from London to Cumbria (pint in 150 miles) noticed smoke in rear mirror caused by oil on exhaust new gasket solved the problem
P D Camp

Thanks guys. There is some drip from gearbox bell housing but it's very little and in fact nothing like what I have been living with for 50 years with A seies engines on Minors. Can't get anyone I trust to fix it in time. I asked why I would use a lot of oil with such high compression readings on the cylinders and was told that could be that the upper rings are OK but oil control rings are defective. I think I'm going to have another go at the tappet seal and see whether I coud get away with carrying a lot of oil for the time being and fix the engine in the winter.
H L Davy

Turned out nearly all piston rings broken one piston skirt had a little chip out of it and valve guides poor. Interesting that compressions stayed very good which deceiving..
H L Davy


H L Davy when did you pull the motor apart? Did you take it on the trip you were going on?

You must have the engine at the machinists now right?
Steven Devine

When did you put the xflow head on, did the high oil consumption start after this?
I put a standard pattern alloy head on my A and it required extensive correctional machining to make it work properly. I had it modified to fit Ford valve seals.
I used 5 litres of oil in a 6000 mile tour of Euope and the UK recently.
Mike Ellsmore

Mike - the car had Xflow head on when I got it. I would not recommend going down that route because the carbs/manifold on the wrong side obscure the ignition components but it does go rapidy and cruises well with 5 speed box.
Steve I got car back yesterday. Got new pistons/rings/big end bearings valve guides/seals. Seems fine now.I could not get the car fixed in time to go to Circuit des Remparts at Angouleme so rode in son in law's MGB. It's a great event.
H L Davy

This thread was discussed between 17/08/2015 and 15/10/2015

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