[Forsaken502]

I was just reading this in another post and had a couple questions.

Jmark:

The redish deposits are normal with todays gas. If money is short, have a machine shop ck the guides and seals. O-ring and umbrella seals are things of the past. Positive seals are much better and will do a good job even with increased stem to guide clearances. The pistons and rings may last a while longer, but its pretty much a crap shoot.

I'm not very familiar with different types of valve seals I was just wondering what the difference between o-ring seals, umbrella seals, and positive pressure seals were. What are the disadvantages/advantages of each were, and if you had to do anything special to the heads to install positive pressure seals. Just thought I'd ask, thanks.

[engineguy]

The premium quality positive seals and made from Teflon and are white in color, avoid any inexpensive subsitutes. There are also some positive seals made from rubber with a Teflon insert that work fairly well. The main thing about a positive seal is that they fit snuggly on the valve guide. In most cases the heads need to be disassembled and the guides machined for the positive seals. It is a very simple machining operation and any high performance machine shop should have the correct cutters.