Classic cars forum & vehicle restoration.

[1935Hillman]

I have yet again an oil leak on my (side) valve chest. I have a small number of NOS cork gaskets but they are shrunk beyond practical use and when I have fitted them in the past they usually leak anyway. I have found literally hundreds of 100% never fail solutions to the problem with an equal number of instances when each of these solutions failed.
In light of what I have just said this may be a really stupid question but does anyone out there have first hand experience of replacing a cork side cover gasket please ? I have used Loctite black gasket in a tube before but this has now failed after a lengthy and hot run.
Looking forward to hearing from you
Many thanks

[Farmer John]

Hello, is this the engine in the rebody project? Superb job on that, I followed that thread.
The sideplate is pressed steel? Unable to see what holds it on, whether it is well located.
Way before considering gaskets, the fit of the sideplate needs to be checked. It is up to you but I would have the manifold off. Remove the paint from both mating surfaces so that the gasket will be on bare steel. That should be easy with one of your chisels!
Offer up the sideplate to the block. It may be that the two surfaces do not come together in which case the surfaces will need checking independently for true using straight edges, flat plates, whatever is to hand. ( The indentation in the sideplate which would keeps the gasket from slipping in, might be too big to fit in the aperture in the block.)
If the two surfaces touch it becomes simple to check their fit. Engineers marking blue is recommended but it is messy stuff to use.
Most important though, tolerances are critical. If you can get it within a tenth of a millimetre it will be good enough for a cork gasket. When we look at mass produced vehicle components it is easy to think that there is no accuracy involved, parts stamped from flat sheets, but it is not the case.
At the time when you can hold the sideplate against the block have a look at the fixing bolts or screws. Do they locate the sideplate, do they allow it to sit where it mates nicely with the block? Are the threads long enough to hold the plate firmly in place? It might be a good idea to scribe around the plate when it is in it's best position.
Preferred method of fitting a cork gasket is to glue it (Ados contact cement) to the sideplate and leave it weighted overnight. The block side has a smear of grease. Cork gaskets need not be overtightened, lots are tightened down with a screwdriver, that gives you an idea of the torque involved. Just as steaming wood softens it so it can be bent, so heating a cork gasket by clamping it between two pieces of metal then heating them to engine temperature will soften the cork gasket. So as soon as the engine is up to temp retighten the sideplate. Check it again next time out, or until it does not tighten any more.
Old gaskets can be rejuvenated by soaking in boiling water and reshaping but then all you have is old gaskets that have been in hot water.
Really, what you do for gaskets will be decided by what you find with the sideplate fit. If it is improved then an old gasket might be worth a try?
Better to find some suitable cork sheet and cut your own, quite difficult to do needing seriously sharp tools, bet you can do it!

John

[goneps]

Sound advice from John, but I would add that plain cork is an unsuitable material for gaskets because, as you've already discovered, it shrinks over time. Replace it with rubberised cork, available in sheet form and in varying thicknesses from motor factors. Rubberised cork is a lot more pliable, will not shrink or dry out, and doesn't need the messing around described by John for plain cork.

Speaking from experience only with the Morris Eight, I agree that the mating faces must be bare metal. Personally I use just a smear of grease on both metal faces so that the cover and gasket will come away cleanly next time.

I've no idea whether the same would apply to your engine, but on the Morris it's possible to fit the gasket upside down and then the faces won't mate correctly. It's only a slight difference, so easy to get wrong if you're not aware.

Richard

[1935Hillman]

Hi John and Richard,

The car is not in fact the rebodied one but another Aero Minx this time with tourer body. the engine is identical however.
The chest cover on the Hillman sidevalve is frankly a poor affair being an ill-fitting steel pressing with two knurled knobs to secure. The pressed 'rebate' is not really wide enough nor square enough and if one has a cork gasket that fits, it will quite readily slip out of line once the knobs are tightened. It is quite a frustrating experience.
I agree that the mating surfaces do need to be bare metal and the limited success I have had with a Loctite gasket-in-a-tube has been when both surfaces are scrupulously clean and dry.
I may try the rubberised cork option next and cut my own. I'll come back when I have tried this and let you know how I get on.
John, thanks for the kind comments, I have quite a way to go but can see the end now (I think its the end I can see anyway!)
Many thanks,
Tim

[MVPeters]

I wonder if the Knurled Knuts are bottoming out on their threads?
or maybe the pressed steel cover has become compressed over the years?
_________________
Mike - MVPeters at comcast.net
2002 MINI Cooper 'S'

[Penman]

Hi
Are we talking about the cover to fill this gap?


If so, I am wondering where the fixing bolts/screws/nuts etc are fitted.
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[1935Hillman]

The threads aren't bottoming out. The original knobs which I don't have, are stepped so that they partly pass through the cover. The knobs I am using are very nice Austin 7 ones but which finish against the cover. This means that more of the stud needs to be outside the cover if you see what I mean and are therefore turned out of their housings a few turns. Hope that makes sense. The cover could of course be slightly misshapen which I will check.
The two holes for the studs are just visible at the back of the chest between the springs. I understand that this is not unusual for such a valve chest and when it seals is more than adequate although when it doesn't seems quite the opposite. Tellingly, the newly built engine in the rebodied car has only been started for the first time last week after more than eighteen months sitting cold and is completely leak free.

[Farmer John]

Hi. The holding nuts. If the originals passed through the cover, were they the means of locating the sideplate and keeping it there? If you can get the two surfaces mating nicely and firmly located you are almost there. The knurled nuts will have to seal on the plate too, hopefully rubber washers will take care of that. If you end up having new stepped nuts made, refrain from having the threaded hole go right through, then the oil cannot climb out along the thread. Because it really wants to! Mr BMC uses unique capped nuts to avoid this happening on his rocker covers, and nyloc nuts on the sideplates. I was thinking of straightening the sideplate as necessary and then building up the face, and where the nuts fit, with a good smear of body solder and milling it flat.

John

[1935Hillman]

Yes John, the original knurled nuts did almost certainly help to locate the cover which the new Austin 7 ones do not. They are also through holes and not blind as they should be. I may have to make some new ones just as you suggest.

[MVPeters]

I wonder if a 'top hat bush' would do the trick?
They're used by many industries in many materials & for a wide variety of purposes, but a web search may provide some ideas & sources.
You might try a 'wiring grommet' search, too.
You'll need the OD of the studs & the ID of the holes in the cover.
I seem to remember that some BMC 'A' series engines use something similar.
_________________
Mike - MVPeters at comcast.net
2002 MINI Cooper 'S'