MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - VALVE COVER GASKET

Now that the 79 MGB engine is completly rebuilt and PAINTED the valve cover gasket is leaking around the entire perimeter and running down the head and block. Yes, I did tighten the two valve cover approx 1/4 turn being careful not to dent the cover. I hope this will solve the problem. If not,is there a gasket manufacturer whose material is more reliable than the present material in use?

The more I drive this rebuilt engine, the better it seems to run. I changed the spark plugs today. This resulted in a higher idle (1100 rpm). Reset the idle to appx 950. There still seems to be a slight "lag" when I accelerate and the power curve seems a bit slow. I have only put about apprx 300 miles since the rebuild. I shall go over the timing and valves in another 500 miles or so.

The new electronic fuel pump is working fine, and no fuel leaks. Replacement of all brake hoses, pads and rotors solved the uneven (side to side) braking when brakes applied.

I think the next item will be exhaust. Need to recoup some $$$$$$$$$$ first. :>{D

cheers

Gary
gary n.hansen

Gary, make sure you have the rubber bushings
under the cups for the valve cover screws.
Without the bushings, pressure is applied
unevenly to the top of the cover causing leaks.
Ronald

Ron, thanx for the info. The rubber bushings are in place under the valve cover bolts. The leak is around the entire perimeter of the mating surface on the cylinder head and cover gasket. We will see how this bolt tightening action works. I seem to recall the valve cover gasket seeped oil prior to the engine rebuild. More than likely the accumulation of grime stemmed the oil flow. When I go over the valves after another 500 miles, I want to use a gasket which is more reliable. :>{D

cheers,

Gary
gary n.hansen

Gary. Some of the new gaskets are not as thick as the originals. Hence, when tightened down, they still leak. I have been using Fel-Pro gaskets, which are available as a seperate part, with no problems. I use hard setting Form A Gasket to glue the gasket to the rocker arm cover, then, set it in place. If you have to use the thinner gaskets, a thin layer of non-hardening Form A Gasket may make them work correctly. You also need to make sure the valve cover is not bent or deformed. If it is, it will not make a good seal regardless of the gasket used. Les
Les Bengtson

It's not so much are the rubber bushes in place but are they new. It's very important that they are new bushes which of course are springy and maintain pressure on the cover. That way provided everything else is OK the cover won't leak.
Iain MacKintosh

As Iain says. Those rubber washers are a service item that nobody seems to change. Things can be OK if not disturbed, but after a long time of getting hot (and sometimes in oil) they take a 'set' and lose their spring. Also as Les says current cork gaskets available to me just don't seem to be thick enough. Even with new cork and rubber gaskets I have still had a leak, until I put a couple of thicknesses of card gasket on top of the rubber washers. If you have the correct 'nuts' that go down through the cover they should tighten on to the shoulder or nut on the rocker shaft and it is that which gives the maximum pressure down through the rubber and cork gaskets to form the seal, you should not be able to deform the cover itself no matter how much you tighten. If you did not have that stop then you would be applying quite a large pressure on the cork gasket and so form a seal, unless you applied so much pressure that the cover deformed and started gaping.
Paul Hunt

I use cork and a thin coating of Hylomar Blue both sides and no leaks. Make sure the surfaces are clean first.
Sam

Our 79 has cork and blue junk and no leaks.

The Miz

I don't mean to dis Les but I wouldn't use the hard setting Form-a-gasket. It's nasty to remove the gasket when it finally needs to be repalced and there are better sealants out there that won't cause that problem.

If the head has been cut the problem may be that the top gasket surface is not straight and slighly bowed causing the leaks. I ask the shop to cut the valve cover gasket side also and make the head completely true.
Mike MaGee

I PROBABLY HAVE USED THE SAME GASKET OVER AT LEAST FIVE OR MORE TIMES WITHOUT ANY PROBLEMS. JUST TAKE A LITTLE RAG WITH A SMALL AMOUNT OF LAQUER THINNER ON IT AND WIPE THE HEAD AND THE VALVE COVER WHERE THE GASKET SEATS. ALSO, WIPE BOTH SIDES OF THE GASKET. BE SURE NOT TO SOAK THE GASKET, JUST WIPE IT DOWN. PUT THE WHOLE THING TOGETHER NOT USING ANY GLUE OR ETC. AND SEE IF THAT WORKS! IT DOES FOR ME AND HAS FOR YEARS!
Cheers:
Dale
Dale & Barb Mast

The gaskets and top bushings are new. The cylinder head is new also - alloy. I do not know what the composition of the gasket is. I suspect if the tightening of the bolts do not solve the problem, either it's the gasket is no good and / or the valve cover mating surface needs to be "reformed" as well as a different material gasket and sealer.

I have used the blue sealer in a tube as well as the red sealer in a tube. I understand the red is better for oil sealing. Again, after another 500 miles when I change the oil, I will go over the valve clearances and look into the gasket issue very closely. I do not like oil leaks.

cheers,

Gary
gary n.hansen

Mike. There is no "dissing" here. We are simply trying to explain our experiences and what has worked for us in the past. My first MG B series engine was a 61 MGA purchased, I believe, in 1975. A friend, who also had a 61 MGA 1600 came up with the idea of gluing the valve cover gasket to the valve cover using the hard setting Form A Gasket. The process has worked well for about 34 years now. But, this does not mean that my process is state of the art, it simply means that it has worked for me over the years.

Thus, if you have a better method, using more modern materials, please let us know. Dale Mast, seems to have used no form of attachement to the rocker arm cover with some success. I tried that, early on, and got substantial leaks from the rocker arm cover. But, it seems to work well for Dale and is something that should be considered.

None of this is about personalities. The only "winner" here is the one who finds his problem solved by a large number of people who have different perceptions of what is best.

Therefore, if you have a better way, please detail it and let us know how you do things. While I may be an "old dog", I can still test out new tricks--things that have changed over the last 30+ years. If you have a better way, tell us about it. Les
Les Bengtson

Just my tuppence worth -

For steel covers I use Hylomar to glue the gasket to the cover and nothing on the head surface.

For Ally covers I use Hylomar to glue the gasket to the head face and nothing on the cover.

In both cases the trick is to NOT OVERTIGHTEN the cover retaining nuts - use new rubber seals and tighten down just enough to nip the gasket - the rubber seals maintain downward pressure that keeps the gasket oil tight.
Chris at Octarine Services

I've found that there are at least two types of gasket available. One is made of pure cork and another looks like some sort of composition that includes black rubbery bits. The second type ALWAYS leaks for me and so whenever I come across a supply of plain cork gaskets I snap them up!
Miles Banister

From what I can see of the gasket material, it appears to be as Mike Banister described. I will look in my spare parts box and see if I have a cork gasket.

Interesting note from Chris @ Octarine regarding the application of sealant on the the alloy head vs. cast head. Care to explain the reasoning behind that thought Just curious.

Thanx to all.
Cheers,

Gary
gary n.hasnen

The comments relate to a steel COVER versus an ally COVER - not HEAD.

Because the steel cover is shaped to hold the gasket and the head is flat, it is best to fix the gasket to the shaped cover with sealant and let the gasket just rest on the head surface making removal of the cover to adjust clearances an easy operation and the gasket reusable.

With the Ally cover both surfaces are flat, so sticking the gasket onto the head means that it forms an oil tight barrier round the head to contain the oil and it also is less likely to be damaged when removing the cover for adjustments.
Chris at Octarine Services

Chris. I was also wondering why you used that method. Thanks for explaining as it makes sense now.

As a general thing, when I glue the valve cover gasket to the valve cover, I set the valve cover and gasket down on a flat surface for about a half hour with some form of minor weight on top of the cover. This tends to guarantee that the gasket will be flat on the bottom, sealing, surface and allows the gasket to bond to the cover properly. Removal of an old gasket is done by carefully scrapping off the old gasket, wire brushing the attachement areas using a brush in a die grinder, then throughly washing out the inside of the valve cover. Les
Les Bengtson

Just for the record; Moss is now offering a set of side cover gaskets and a Valve cover gasket. they are said to be silcone rubber with fabric reinforcement. sold as #296-425. I plan to order a set with my next order. I sahll report on them in a thread. Bob Thompson
Bob Thompson

I have never once had an issue with leaky rocker cover gaskets. I usually get 2-5 uses from one gasket. I have found a light smear of grease or oil on the head is useful for being able to separate them cleanly later.

I have always used cork and on at least one occasion I had to glue two together to make it thick enough (only until the next lash adjustment).

I have placed them dry on both faces (when the gasket was slightly oversized and properly shaped so it would fit snugly in the cover).

I have glued them to the cover with gasgacinch (when not so well formed... also a pain to replace later).

I have used silicone form-a-gasket (I don't recommend this one as it was messy and a pain to get a nice even surface).

I have also used hylomar. This is my current method when the gasket is ill-formed.

Another reason to put the adhesive on the cover is it is much easier to scrape than the head, or rather, it is easier to do without getting bits of gasket in the motor. A very good reason to NOT put adhesive on alloy is it is very difficult to remove without damaging the surface.

As an aside, I have also noted that you cannot overtighten the hold-down nut as it is tube-shaped and seats on the head-nut (if you have the proper washers in good condition in place). However, it is possible to have the stud too far out and have the tube-nut "bottom-out" before snuging up properly.

mike!

Got to the valve cover gasket today. Use a black RTV sealant formulated for oil sealing gaskets and high temps. Upon removal of the valve cover, I discovered the gasket was cork composition. The problem was the gasket was kinked inward allowing oil to seep out.

Next item. As the valve cover was off, I adjusted the valves cold to a "relaxed" .014" Many of the valves were opened to .020-.023" and make some clattering as the engine went down the road. Yes, I still have a clicking, but that is life with solid lifters.

Now this car runs absolutely great. :>{D

Cheers

Gary
gary n.hansen

Are the threaded studs holding the valve cover gaskets supposed to extend 1 - 2" above the cover? Doesn't look right.
Bryan

Hey my friend you mention a slight lag as you accelerate i had the same problem and someone told me to top up the dash pots on the carbs with 20/50 oil it solved my lagging instantly
Good Luck
Richard H
Richard H

This thread was discussed between 23/08/2004 and 03/09/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.