Engine: What is a better gasket cork or rubber and why?

[G T Joe]

What in your opinion seals better a cork or rubber gasket , or do you use silicone RTV sealer? Does anyone supply cork - rubber gaskets for Studes?

[Mike Van Veghten]

Sealing wise....equal.
Holding shape during the squeezeing of tightening the parts, I like cork/rubber (or plain cork).
Plain cork is normally fairly brittle.

I normally use RTV as an "only" sealer. That is, no other gasket. Though I have used it with various gaskets, it's not normal.
I like the Hylomar sealer with most any gasket material. Sorta expensive and its shelf life is short, but for a good seal, it's VERY hard to beat it. Copper coat in head gaskets.

Mike

[Skybolt]

It depends on where it is being used. For example, the valve covers I find that if using the cork gaskets they will deteriorate faster than the "rubber", for lack of the right compound name, because of repeated adjustments of the rocker arms. For that I use RTV or similar to attach the gasket to the cover as a semi permanent deal and it will last many years of repeated on and off use. The cork ones will not take this type of abuse. If all mating surfaces were machined to today's manufacturing standards one could just use RTV but most of us don't have our engine parts at that standard. In other areas I don't mind which type is available although it would be nice to have neoprene or similar material for the oil pan, timing cover and the valley cover as these are the other places that might be removed numerous times in the life of an engine before a major rebuild. I did at one time have a valley cover gasket that was reusable but have not been able to locate one lately. Similar options are available for the rear differential cover which makes it easier to do work on it without having to scrape gasket material off each time. It is usually a personal preference not any mechanical advantage.

[Flashback]

In my opinion (not worth much), the answer is Fel-Pro gaskets. The materials they use have proved to be the best for me for many years. Different materials in different places. And they do it right.