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MG MGA - Engine Oil Loss

A query for the group that I have been struggling with for some time.

My A 1500 uses more engine oil than my 40 years experience of As expects, i.e. about 200 miles/pint (400 per litre for Europeans). Also I get a smell of oil particularly when pulling hard. I do not appear to burn oil as blocks are light coloured, and my compression readings are 140,153,144, and 140psi. I have re done the rocker cover gasket. It would appear that I throw the oil out of the breather on the side panel of the engine. I have tried lengthening this with a bit of garden hose but there is still evidence of burning oil on the outside of the first bend of the exhaust pipe, hence the smell. A friend in the trade said it sounds like 'rings' but this doesn't really check with the compression readings

All ideas welcome a specific question.

Why does the A have two breathers, side and rocker cover? Could I block the side one hence the oil would go up to the rockers and possibly then escape by that breather into the carb, at least then I wouldn't smell the oil when driving? Would this be OK?

All ideas/comments welcome. By the way otherwise the engine runs very well at present.

Paul Dean

It is possible to have good compression numbers and bad rings burning oil. The truth is in the blow-by through the crankcase.

Two breather ports is necessary for proper crankcase ventilation. See here:

If you plug the draft pipe on the tappet cover you will defeat crankcase ventilation, and it will result it loading up oil in the air cleaner as crankcase exhaust goes the wrong direction.

The cure for tired rings is new rings (minimally). This should include ridge ream and hone the cylinders. If the cylinder walls are badly worn, then re-bore and oversize pistons.
Barney Gaylord


Thanks for your response here and the explanation of venting on your website. It helps me make up my mind that I better get on and rebuild the 3 bearing B engine that I recently bought.

I presume there is no great urgency to sorting out the piston ring problem as long as I can cope with the oil consumption and smell?

Thanks again.

Paul Dean

This thread was discussed between 09/07/2013 and 10/07/2013

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