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MG MGA - Oil under the head gasket ????

Hi Guys, Periodically I use a small light to see whats going on in the combustion chamber through the sparkplug hole. After replacing the head gasket with the black Payen version I had a look and saw what appears to be about a teaspoon of oil sitting on the top of all four pistons. So I lifted the head and saw that the underside of the head gasket was soaked in oil. I replaced it with a new one, torqued it up and after running the engine up to temperature checked again and sure enough oil in all four chambers. I get no smoke out the back when engine hot and reved up, the valves where dry and clean, and the spark plugs are not fouled. I can only think that oil is being forced up from the cam followers somehow. The only thing I have done recently is replace the timing chain and sprockets and installed an oil thrower disc that was missing. I cant believe all for piston ring would fail at the same time so I'm discounting that. Any ideas would be very much appreciated as this is doing my head in.
Thanks Alan
AR Terry

Can't understand that
If you had a teaspoon of oil in each cylinder it would be as smokey as--
Was there a specific reason that you looked in the plugholes originally or just inquisitive
Also; when you removed the head, was it in fact oil that was in there on the pistons

willy
William Revit

I think Heisenberg is somehow involved. You shouldn't look!
Art
Art Pearse

Maybe not oil. It may just be an odd reflection. Try a long cotton swab to see if it is really wet on to- of the pistons.
barneymg

Thanks guys.

Willy, reason to look was that the last time I hade the head off I noted some small pre detonation markings on top of the pistons, smoothing out all the sharp edges created when the head was skimmed sorted that out. It is definitely oil Barney.
I haven't actually driven the car to put the engine under load yet so it may well show the expected symptoms of oil in the combustion chamber then. May do that tomorrow if feeling brave.

I can only think of three ways oil could get into the cylinders; Past the valve seals; Past the piston rings or somehow from the cam followers space. Other than that perhaps the head gasket is failing (again) but there's no water in there. Any ideas on how to pinpoint the problem would be greatly appreciated though it looks like the head will have to come off again Damn.
Alan


AR Terry

When you remove the head, oil usually gets all over the gasket. So you may be seeing residual oil from the removal process. As for the oil on the pistons, do a leakdown test and you'll know whether it's valves or rings.
Steve Simmons

Is your crankcase breathing system functioning?
Allan Reeling

What do you mean by "CAM FOLLOWERS SPACE"? Are you suggesting the block could be porous?
A J Dee

Worn valve guides may allow a SMALL amount of oil into the combustion chamber, especially leaking around the intake valve stems which are under vacuum in the intake ports. This will eventually make carbon deposits in the combustion chamber, and can cause smoking out the tail pipe, especially with throttle after coasting or after a gear shift. I have seen a few cases where it was so bad as to spew oil droplets out the tail pipe to oil up the windscreen of the car following, and using as much as a quart of oil every 50 miles. This condition may also include badly worn piston rings.

However, even in the worst conditions it has never accumulated a puddle of oil on top of the pistons. If it was to do that, it would most likely occur after a prolonged period of idling, while sucking oil down the valve stems and not blowing it out the exhaust.

The oil consumption may be significantly reduced (temporarily) by installing umbrella seals on the valve guides. But in the end the real fix is to replace valve guides while doing a valve job, and maybe new piston rings during a complete engine rebuild.

Oil on top of the cylinder head (from the rocker shaft assembly) runs back to the sump through the clearance holes around the pushrods. There is no connection between these ports and the combustion chamber. For oil to get from the top of the cylinder head into the combustion chambers would require a leaky head gasket, and it is very unlikely for the head gasket to be leaking into all four cylinders at the same time.

The only other oil connection between block and head is one hole at the back that supplies oil from the rear cam bearing into the head and upward through the rear rocker shaft pedestal. It is unlikely, but a leak there past the head gasket would oil up the rear cylinder only.
barneymg

Thanks to all for your comments. I have come to the conclusion that the problem is with the Black Payen head gasket as that is the common factor; Two fitted with the same result. I have noted that the holes in the Payen head gasket for the push rods to go through are significantly larger than those on an original gasket, that it is thinner than an original and that it is just a hole with no supporting copper or ally rings. If you have fitted a Payen black gasket it may be worth getting anal and sticking a light in the plug hole to see whats going on, you may have the same problem.
Thanks again for your interest and helpful comments.
Will report back in due course.
Alan
AR Terry

I don't think it's a problem with the Payen gasket. I have used then for decades with no problems. There are no grommets around the pushrod holes because there is no pressure there, just drain holes back to the sump. If it would leak there, you would have a compression leak from chamber to sump, not the other way around.

Look for a different source of the oil on the pistons. Being all four cylinders, it is likely to be worn valve guides or bad piston rings, not a single source leak of the head gasket.
barneymg

BUT
You have said there is no smoke and the valves were dry---ran the engine up to temp
no smoke but oil on the pistons----????

, if there's no smoke there's no oil
You need to get an ear bud or something in there and take a sample---what you are describing is almost impossible,
willy
William Revit

This thread was discussed between 22/10/2017 and 24/10/2017

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