Tappet Cover Gasket
- by Ian Moorcraft
- Download this article here
We have all changed tappet cover gaskets trying to stop oil leaks only to find after a few miles you are back where you started. Some of this is down to poor alignment of the cover on the pre 1932 flat type tappet covers.
On these early blocks the land at the top of the block is so minimal that a good seal is difficult to achieve. It’s hard to see why the top land wasn't designed of similar depth to the sides and bottom, this can cause oil leaks and more fumes than is considered normal.
The later redesigned strip cork seal cover is far superior, but unfortunately cannot be fitted to these pre 32 blocks.
You can see in the photo below, a standard cover fitted without the gasket and when lifted up as far as the holes will allow, there is actually an open gap into the valve chest along the top.
You normally find that after a while in service the top of the cork gasket expands in the heat. It then slips out from under the cover and forms a pocket for the oil to collect between the cover and the gasket putting even more pressure on the bottom joint to hold oil.
Check your cover for fit, if its like this one file the fixing holes at the bottom to allow the cover to be pulled up tight under the block. I always stick just the top of the gasket to the top of the tappet cover with Evo-stik impact adhesive to keep it in place. I also punch two extra holes along the bottom of the gasket for extra drainage.
I have never had a gasket slip out since the top was stuck down, so worth thinking about the next time you change the gasket.