Valve chest cover leaks - again!

[Old Dave]

I found a couple of threads that suggest the silicone seal is the way to go with the valve cover seal. I have fitted one but it still leaks in the bottom corner - too much to ignore.

Obviously the fixing bolts don't want over-tightening, or else they would have some means (hex head etc.) to apply more effort.

finger tight is a variable torque and the knurled edge tears my skin as I get older.

Can anyone give me guidance as to the the best way to get a reasonable seal?

[Reckless Rat]

Hi Dave. I had exactly the same problem, but I discovered that it wasn't the silicone gasket that was leaking - it was oil mist coming out of the 4 vent holes and settling on the rear lower corner of the cover and being blown rearwards by the fan. This venting wasn't due to wear in the engine because it has recently been rebuilt, but may have been exacerbated by a good seal on the oil filler tube.

I have since modified the cover to allow it to vent below the chassis rail. It has cured the problem.

The secret of getting a good seal here is cleanliness. First of all give the inside of the valve chest cover a good clean with acetone and then stick the silicone gasket in place with superglue. Also clean the mating face on the block in the same way (with acetone), and assemble the joint dry. It doesn't need to be too tight.

Check that the cover is flat before assembly. Overtightening tends to distort the cover. I also made round gaskets for the fixing screws out of silicone sheet.

If you're going to solder on an elbow and block up the remaining vents, make sure you leave enough room so that it isn't contacting the underside of the exhaust manifold.

[Steve Jones]

I got a bit fed up with the tin Tappet Chest Covers some while ago and now, with one exception, all my engines have these. They don't leak. 

   

Steve

[Peter Clayton]

I found that if you fill the grove , normally used for a cork gasket , with silicon and leave for a couple of days to fully cure. (get the surface as smooth and level as possible  which may take a couple of coats ) Then cut out a card gasket , which should be a full cover not just edge type, cut holes for the securing knurled studs  and  drain holes at the lower edge to return any oil to the tappet chest, smear the cover sealing edge with fresh silicon and do the same to the block face , ( note, just a smear) assemble  and tighten securely , all should remain oil tight . As an extra precaution I have drilled a small hole in each knurled nut and wire them together to prevent unscrewing.  You may still have some  oil misting but no leaks.

[Old Dave]

Thanks All for the advice. It maybe that I wasn't "clean" enough applying the silicone gasket. I hadn't realised it was critical. So I might have a go at redoing the job for starters. If that doesn't work I will have to take the more active ideas suggested.

Thanks again.