excessive oil use

[Stoneporch]

My 1275 engine has compressions of 150 on all cylinders, there is no sign of foam inside the oil filler cap and no sign of water in the oil. Oil does seem to be being forced out between the head and the block (the dipstick is always spattered even after only a few minutes use), so I intend to replace the head gasket. The engine is currently using/losing about a pint of oil every 80 miles or so.Mainly using, I think, as there are no oil drips when I park. Is there anything I should do whilst the head is off to attempt to reduce oil consumption?

[bmcecosse]

Sounds like there is excessive crankcase pressure - do the oil cap test.. With engine hot and idling - remove the oil filler cap and rev up. Is there a plume of smoke/fume ?? If so - the bores/pistons are worn. Your 150 compression is poor for a 1275. I doubt there is any problem with the head gasket - but if you do remove the head, you should check for wear in the valve guides - and make sure (or renew) the seals are on the inlet guides. You can of course also check the bores for wear - and perhaps remove the pistons to inspect the rings - and perhaps fit a new ring set - in which case be sure to 'glaze bust' the bores.

[Stoneporch]

Thanks for that BM. Plenty to look at!

[bmcecosse]

I'm afraid so....

[IslipMinor]

150 doesn't sound great, and could certainly lead to crankcase pressure. What breathing arrangement do you have on the engine? Can you post some pictures?

The 1275 should have the canister on the timing cover with a hose going either to a PCV valve in the inlet manifold, or to the port on the side of the carburettor. The rocker cover has no vent connection and the oil filler cap must be the 'vented' type.

The system uses inlet vacuum to draw filtered air into the crankcase through the vented filler cap and sucks the fumes into the inlet tract where it is ingested by the combustion process. The partial vacuum helps to keep the oil the right side of the rear main scroll and it works!

When you refit the head make sure that you fit 'lip' type valve stem seals to the inlet valves to prevent oil being sucked down the valve stem. Exhaust valves do not need a seal, as there is some pressure in the combustion chamber whenever the exhaust vale is open.

[bmcecosse]

And they need to be well lubricated -especially with leadfree fuel.

[Stoneporch]

Thanks for the above replies.
I have just done the rev-up with the oil filler cap off test. No smoke from the oil filler but smoke from the carburettor side of the engine-possibly from the badly sealed exhaust/manifold connection. I will look at the breathing arrangements tomorrow.