Knowing little about a XPAG automotive engine for a 51 MGTD MkII, I am
asking what can be done to lessen the oil usage. First a little history.
The engine was rebuilt in 1978 by previous owner. When I got the car a
year ago, it ran good, but number four plug was always getting fouled up
with oil. Other three plugs were dry. Oil pressure was between 60 and 80
psi, depending on speed. My oil consumption was low. Then the crankshaft broke!
During rebuilt, the machine shop discovered the cylinders had previously
been bored to plus .038, yet .040 rings and pistons had been inserted.
Very tight, lots of friction, LOTS OF HEAT. However, boring the
cylinders now for plus .040 cleaned up the scoring. The manual for a
MKII says compression should be between 110 and 150. Before the crank
broke, the compression was 175! I was suspicious about the high reading,
but didn't know why at the time.
Now the engine has been rebuilt with new rings and pistons, tappets and
crank, plus seals and gaskets. The original valves and guides and cam
were retained since there was only 9000 miles on the 1978 rebuilt engine
when the crank broke. This time the valves were ground and the seats
checked okay.
I have now put on about 3000 miles on the newly rebuilt engine. My oil
consumption is about 600 miles to the qt. Before the crank broke, it was
about a qt every 2000 miles. All four plugs are now fouling up with
oil, before it was just one plug. However, my compression is right up to
snuff, all reading between 145 and 150, the maximum according to the
manual. My oil pressure is still, as before, between 60 and 80 psi.
How is the oil getting into the combustion chamber? Would lowering the
oil pressure help and how would that be accomplished? Is there any
additive I might put into the engine that would gradually seal up
wherever the oil is seeping in? Engine runs great but I'd like to
eliminate the higher than normal oil consumption which is fouling the
plugs (though I am told by a previous dealer of MGs that the Abingdon's
policy said, if consumption was less than a qt per 500 miles, don't worry.)
Stu Keen
Venice, Fl
simbafish@home.com
51 MGTD MKII
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