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Tappet chest leak.
#1
Could I ask if anyone has had any good results with the silicone seals that are available for the 
tappet chest covers please?
My 3rd attempt this year with using the original type cork gaskets has failed once again.
Rightly, or wrongly, I have always had to trim them using a craft knife to fit them into the cover
and have repeatedly had to straighten the cover to achieve a flat surface but still they don't stop 
the oil seeping out, usually in the bottom corners.
Any suggestions or full proof methods will be greatly appreciated.
Thank you
Graham
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#2
I have used a good number now with excellent results.

I glue the silicone into the cover with Tiger Seal, or similar, leaving it to cure overnight before fitting completeley dry (both surfaces).
Whatever you do, don't take my word for it!

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#3
I recently acquired a cast alloy cover from a side valve Reliant
The mating face of this cover plate has a milled recess to hold
an O-ring, but I’ve not run this engine in anger yet!

There’s a cast alloy Cambridge cover plate on EBay today.

Regards

Bill G
Based near the Scottish Border, 
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#4
Many thanks to both of you for your replies.
Ruairidh, may I ask if the silicone gaskets that you used were in conjunction with a 
standard cover or with an upgraded type please?
I would of course prefer to use the one I have if suitable, but did wonder if one of a stiffer 
material/ design might be required.
Thanks again
Graham
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#5
I have been using the silicone gasket for about six-months now in a standard pressed steel cover, and I can report that this has not yet leaked! I have done several thousand miles in the interim.

The problem with the cork is a square profile is being fitted into a rounded channel, it has to be trimmed to fit and the success or not depends on how well the trimming is done, I had a reasonable success, with sealant, but so much easier using the silicone gasket. I glued the silicone gasket with dabs superglue to hold it in place when fitting the cover in place.

Will be using this on my other engine in due course.
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#6
(29-12-2018, 06:51 PM)Graham Honnor Wrote: Could I ask if anyone has had any good results with the silicone seals that are available for the 
tappet chest covers please?
My 3rd attempt this year with using the original type cork gaskets has failed once again.
Rightly, or wrongly, I have always had to trim them using a craft knife to fit them into the cover
and have repeatedly had to straighten the cover to achieve a flat surface but still they don't stop 
the oil seeping out, usually in the bottom corners.
Any suggestions or full proof methods will be greatly appreciated.
Thank you
Graham

Hi Graham, I will share with you what I do,  they don't leak when done.
I use the standard cork gasket-untrimmed with the joint cut at an angle at the top of the cover.
The cover is fully degreased.
Put silicone gasket goo round the recess of the cover then put the cork in. Put a tiny bead of silicone onto of the cork.
wipe a tiny bit of oil around the joint face on the block.
Put the cover on gently tighten, leave for 12hrs remove any excess silicone and then "nip up the thumbscrews" do not over tighten.
For me the great thing about this, is that you can at a later stage remove the cover adjust tappets and replace cover as is (do not over tighten).
Incidentally I recommend using dowty washers on the thumbscrew shanks (much better than the useless fibre washers washers).
I hope this is successful for you.
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#7
Hello Graham,

I also use completely standard Austin covers.
Whatever you do, don't take my word for it!

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#8
Thank you Gary for your reply.
Would I be correct in thinking that the seal is a "D" profile and if so do you
glue the flat, or curved, surface to the cover please?
Thank you
Graham
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#9
The seal is D shaped and this should be glued into the cover leaving the flat surface dry and ready to press onto the block side. They can be taken on and off without issue provided all surfaces are cleaned before reassembling.
Whatever you do, don't take my word for it!

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#10
Hi Graham,

The type of gasket you use is not all important.

The way you fit it is.

The problem of the cork, is because it's square you are pushing in the corners harder to get it to hold.

The same will happen with the silicon gasket.

Half the answer is what R is doing. Useing a glue or sealant. As this will stop the oil from leaking between the gasket and steel cover.

The other half is because you have pressed the corners, the gasket is no longer flat.

I use an O ring material. But it doesn't realy mater what you use.

It's cheap to use a clear bathroom sealant as your glue, 

half fill the lip round the valve chest cover, with silicon sealant, fit what ever gasket material you like. Sit it on a flat piece of wood. And clamp firmly overnight in a vice. Remove carefully from the wood the next morning.

The gasket will be flat from the wood, and the silicon sealant will hold the gasket, and seal behind it.

If not buy an aluminium cover, being stronger. They press more evenly over the full area.

Tony.
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