Cam Cover Gasket Sealant

'51 XK120 with 8 stud cam covers, not the more usual 11 stud covers.

Chasing down an engine miss, I found it was oil flung up by the timing chain, leaking from the intake cam cover at the lower front corner, blown back by the fan and getting all over the distributor cap, shorting out the spark.

I think I last had these covers off about 15 years ago, and at that time used Permatex No. 2 which was supposed to be non-hardening. I think the heat of the XK engine must have been too much for this stuff, because it was crumbly coming off. So I think I am done with that stuff; time to move into the 21st century. I wonder what they used in 1951, shellac maybe?

The Napa Auto Parts store had quite a few choices of sealants, and I picked Permatex Optimum Black which is supposed to be good for 500F or 260C with maximum oil resistance. The tech data sheet says it is good for valve covers.

It comes with a nozzle that you trim off to the size bead you want. I put down a 1/16" bead, then the gasket, then another 1/16" bead. Then the cover, washers, and nuts finger tight and let it sit 2 hours to set, but I noticed the gasket tried to schmooze out so I had to push it back in. Without the 3 studs at the front there is nothing to hold the gasket in place until the sealant cures.

Then after 2 hours you tighten the nuts another part of a turn. Wait 24 hours to cure.

They also had Permatex Optimum Grey which is supposed to be good for a higher temp at 700F or 371C, which I thought might be good for an XK engine, and is recommended for intake and exhaust manifolds, also good for valve covers, and says it is oil resistant, but it did not say maximum, so I chose the Optimum Black.

I wonder if anyone else here has used either of these?

IMO, the 21st century solution is Cometic gaskets. I’ve been using them since Terry’s started carrying them 15 years back or so, and I’m only on my second set. Since you don’t use sealant, they’re fully reusable. There’s no fuss getting the cover loose, and no hassle scraping off old gasket or goop.

They’ll only make up for so much sin though. I wanted mine perfectly sealed so I went around the edges a lightly tightened cover with feeler gauges and marked the gaps with sharpie. Then I hand machined the edge of the cover using a fine oil soaked file, and emery paper. By doing that the gap was reduced to less than a couple thou, even in those impossible to seal corners.

You also need to seal the down studs because oil sits on top and drips down the threads. They can be a major leak source (at least they are on a 3.8/4.2)

I’ve used Permatex Ultra Copper on my Triumph, Landie, and the MKII for years. I even used it on my old Jensen Healey. Only the JH ever leaked, but then you’d need whatever they use to seal nuclear reactors to stop JH cam covers from leaking…

I wonder if anybody has Cometic or other rubber gaskets for the '48-'51 cam covers? How would you hold them in place?

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Plus one for the Cometic gaskets.

Prior to going to those I used the paper gaskets with The Right Stuff sealant on either side. No leaks but be prepared to work to get the cam covers off and then scrape the sealant off of the head and cam covers.

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Loctite 515 seems to do the trick. Faces must be totally oil free on application, and obviously pretty well flat across the whole face.