Head Gaskets

[Rodd]

I was thinking the other day when I was cooking dinner about head gaskets. (You'll see the tie-in in a second) What are they made of? Every month or so we see a thread where someone blew threw their head gasket. How strong are they. Obviously over time they must deteriorate a bit. Here is my thought for gasket material. While I was cooking we have silicone (I think) cake pans, bread pans, etc. They are very pliable, durable, and the temp rating is nearly 1000 degrees. I was thinking those would be great for head gaskets. Never having to replace a HG I don't know if is is doable. I do recall seeing them used a valve cover gaskets somewhere. Why wouldn't they use the same material like those pans as a HG? Any thoughts?

 

[Franko914]

Hello Rodd,

Most important characterisitic of the head gasket is it MUST be able to retain/maintain torque values over an extended period of time while providing a high compression seal.

If the mating block and head surfaces are perfectly flat and perfectly smooth and the head bolts/studs are torqued down in perfect sequence to perfect values, then retorqued after a certain number of hours of engine use, you could probably get away with using just coppercoat spray. But, nothing man-made is ever perfect... So, there's a plethora of theories, philosophies and choices on head gasket material that can maintain torque values and provide a long lasting seal.

So, in answer to your question, the mating block and head surfaces must be flat and smooth enough (subjective) to use a very very thin layer of silicone as head-block gasket material.

Regards,
Franko

 

[bk95td]

According to what bill heath told me :most head gasket failures are caused by the tty bolts. They can't retain their torque value under heat. That is the reason I will only use arp head studs. Much much better material,more thread engaugement and reuseable. worth every penny.

 

[TomMac95]

There's also:
- the matter of sealing against formidible pressure peaks in a diesel.

- the problem that heads/blocks expand/contract somewhat differentially.

- the problem that over time , the sealing surfaces are subject to corrosive decay.

>Silicone could handle the corrosive forces , but not the pressure/temperature peaks.

On my VW diesel , the aluminum heads were forever developing grooves, about half the thickness of a human hair , which leaked gases past the gasket.
On my 6.5 the thin steel sealing ring worked , but there was corrosive pitting immediately adjacent, necessitating resurfacing of the block firedeck before installation of my new heads.

 

[bk95td]

If you look at how narrow the sealing surface on a 6.5 is, it is truely amazing that they hold for as long as they do. Very narrow to the water jacket and a large area with no bolts where the exhaust ports are.As said previous, The bolts, the constant heat-cool cycles and extreme pressure are big obsticles to over come.