Silk thread for gaskets

[texasSlick]

@MexicoMike

The use of silk thread originated in sealing the case halves of light aircraft engines. A non hardening sealer was used with the thread. The thread prevented the sealer from being squeezed to zero thickness and otherwise did nothing.

Used with conventional gaskets, the silk or fine copper wire increases the local clamp force as FE has explained.

Slick

 

[SteveA]

Yes.

But of course WHICH sealant would be another thread all by itself !

On the 920 I used the JS method of Pliobond and copper wire. It does seem to work, but the copper wire was horrible faff.

Pliobond works! No doubt. Assuming you don't mind taking a hammer to a block of wood when removing the head next time!

I've settled for a smear of Wellseal on (annealed immediately before use thinner) copper head gaskets (supplied by JSM!).

 

[robs ss]

Yes.

But of course WHICH sealant would be another thread all by itself !

On the 920 I used the JS method of Pliobond and copper wire. It does seem to work, but the copper wire was horrible faff.

...and you think silk thread will be less of a faff??

 

[MexicoMike]

The issue is not the head gasket joint sealing.

The common (ish) issue with Norton engines when using a solid copper gasket is oil weep from the pushrod tunnel area. This is more pronounced when using alloy barrels.

The idea is that putting thread or wire around those pushrod tunnels help the gasket acquire more clamping force at that specific point whilst not interfering in any way with the head gasket joint.

At least that’s the theory as I understand it.

Ah, OK... Pushrod tunnel sealing! Makes perfect sense - luckily I haven't had that sealing problem. I was working really hard trying to understand how silk thread could possibly handle combustion chamber heat and pressure!

 

[jseng1]

When racing I had some oil seepage with both composite and copper head gaskets (before I developed the pliobond as suggested by Ron Wood and added fine copper wire). My solution was as below. The Copper wire would flatten out.