Rubber Gasket Compression

[inline6]

Hi i'm adding a different gasket design using sheet nitrile 3.2 mm thick 60 shore harness. How much compression would be a good ballpark to use to seal up a valve cover? i'm thinking of using a 2.5 mm spacer to limit compression to 0.7 mm to avoid over deforming it as its not as rigid as some materials. it is not a high pressure situation just whatever you typically get in a valve cover of naturally aspirated engine. the gasket is 11,000 mm^2 area and there are 8 M6 bolts clamping which can easily clamp 50,000 N

Does anyone have any rules of thumb?

 

[Tmoose]

What engine?
Is there no commercial gasket available?

What construction is the valve cover?
Stamped sheet steel covers of 60s vintage would deform locally under the slightest over-tightening. The clamp pressure would be quite uneven even before the cover bent permanently.

 

[inline6]

there are gaskets available but im wanting something thicker to provide additional clearance and something slightly more deformable. it is a cast alloy VC and reasonably stiff. the V/C has been used and is flat, they don't seem to deform permanently unless damaged