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MG MGA - Oil inside the top tappets cover

I have noticed recently that not enough engine oil seems to be reaching the tappets area on top of the cylinder head. Is it possible that the hole/s through which the oil is fed are blocked with gunk? If so, is there any engine oil additive which would work on cleaning the oil passages, without having to remove the head? I have heard about a product called Seafoam which might do
this job quite well. Can anyone here confirm or otherwise whether this stuff is good enough and is recommended.

Thanks

Frank
F. Camilleri

I would not use additives in the oil.
Why not clear the passages with a piece of wire?
You do not need to remove the cylinder head, just remove the rocker shaft pedestals.
Check that the hole in the pedestal lines up with the hole in the head and clean the passages with the wire.
You can pass the wire down the hole in the head and into the engine block.
Also clean the pedestal drilling.

Mick
M F Anderson

Wire probe will not work that way.

Vertical oil hole in the rear rocker pedestal lines up with hole in the head. Later year MGB heads (which might be found on an MGA) have hole in the head a bit farther forward. In this case the rear pedestal needs to have a small "toe" on the font side and shallow slot in the bottom to reach from center of the pedestal forward to catch the hole in the head. If you have a later head and earlier pedestal, it should be obvious without disassembly, as the pedestal bottom edge will be straight across (like all the other pedestals) while the head will have a small plateau extending just forward of the rear pedestal. The point is, if you have an early rear pedestal on a later model head, there will be no oil getting to the rocker shaft. If you have any oil at all getting to the rocker shaft, this is NOT your problem.

You could remove the rear rocker pedestal by removing one head bolt and one pedestal bolt and the rear rocker arm; good way to change the pedestal. But even then you cannot probe a wire down through the head into the block. The oil hole in the head goes only part way down; then there is a horizontal holed drilled from back end of the head (and plugged at the back), and another vertical hole drilled up from bottom of head near the back of the engine. It will be impossible to push a wire down through this "Z" shape labyrinth from top of head into the engine block.

In the block, the oil supply port to the head comes from the rear cam bearing. If the rear cam bearing is installed wrong, holes in the bearing shell may not line up with holes in the block, resulting in no oil getting to the head. The engine has to be substantially disassembled to R&R the rear cam bearing to correct this problem. But if you have a small amount of oil getting to the rocker shaft assembly, then this is not likely to be the problem.

In fact you may have no problem at all. The rear bearing journal on the cam shaft has an annular groove to conduct oil from oil hole below to oil hole on top. The hole on top is offset slightly forward from hole on bottom and does not line up with the groove in the cam bearing journal. There is another short groove in the cam bearing journal running back to front to join the annular groove to the top hole. This short groove rotating with the cam comes into alignment with the top oil hole once each revolution of the cam.

This provides a short pulse of oil to the rocker shaft assembly once each rev of the cam, or once every second rev of the crankshaft. This "obstruction" maintains oil pressure in the block while providing a small pulsing oil flow to the rocker shaft assembly. Amount of oil getting to the rocker shaft varies some from engine to engine, but it is generally low flow rate.

If you have some oil on top of the head it is likely to be normal, nothing wrong. Small normal oil flow will dribble a bit of oil from the rocker arms to spatter oil inside of the rocker cover. Running the engine with cover off should result in some oil spatter outside of the engine. If it rubs with cover off and no outside spatter (which would mean dry inside valve cover), then you have a problem with no oil to the rockers. But if the rockers are wet with oil, it should be okay.



Barney Gaylord

Hi Barney,

I should stay with my speciality, the Twin Cam version of the MGA.
I have only done some work on the MGA pushrod engine.
At least with the Twin Cam you have an external oil pipe carrying oil to the valve gear.

Mick
M F Anderson

Thank you Mick and Barney for the information submitted. I have now decided to lift the head off and have a good look. I will also poke the oil passage with a length of wire while the head is off.

Frank
F. Camilleri

Frank, after you've removed the head, crank the engine and watch for a pulse of oil coming from the hole in the block. If after 10 or so revs you don't get any oil, you'll know the problem is at the rear cam bearing.
MAndrus

This thread was discussed between 11/02/2017 and 15/02/2017

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