When an O-ring is used instead of a head gasket, what type of O-ring material is used? The regular black buna type does not have a very high heat rating at 250 degrees. I don't know if this matters because the temp may not get that high at that point of the head. Silicone and viton can handle up to 450.

I have been making water cooled heads for Odysseys. I could recess the combustion chamber by the gasket thickness and put an O-ring groove in. The water temp runs about 170.

 

I see the Viton o rings but I only use .021" steel wire and I have never had a failure.

 

I thought they were a type of silicone based material.
ERIC

 

Viton Orings are used on the domes and nitrile everywhere else.

 

Seems to be a good topic to ask my question. Would any of you know what material to use in place of the o'rings or a better rubber than the regular black for adding a little nitromethane to my alcohol? The standards have always held up well to race gas and alcohol, but I have been told the nitro will eat it up. Any help would be appreciated.Bubba

 

You could use Kalrez (made by DuPont) it is very chemical resistant and is good for 500 or 600F depending on the compound. They are pricey though it could cost $300. There is also Chemrez (don`t know the manufacturer) that is slightly cheaper and has similar properties. Check with a local industrial supply house that sell gaskets, o-rings and other sealing devices. HTH

 

I started this thread a while back. Since then, I have continued to use Buna-N (nitrile) except for the ones sealing the combustion chamber. I use viton for that.

Here's some info on a few types:

Buna-N (nitrile) O-rings are the most widely used for sealing applications. They effectively resist petroleum-based oils, hydraulic fluids, most silicone fluids, and nonaromatic fuels. They resist taking a set after being compressed, they have high tensile strength, and high abrasion resistance. Buna-N is not compatible with phosphate esters, ketones, or brake fluids, strong acids, and ozone. Durometer is Shore A: 70; temperature range is -35° to +250°F

Viton: Viton (fluorocarbon) O-rings offer a wide spectrum of chemical compatibility and temperature-range adaptability. Use with petroleum products, diester lubricants, silicone fluids, solvents, and acids (except fuming nitric). They have good resistance to taking a set after compression, and low gas permeability. Great for hard vacuum service. Not for use with acetates, methyl alcohol, ketones, brake fluids, hot water, or steam. Durometer is Shore A: 75; temperature range is -31° to +400°F (except metric sizes, which have a temperature range of -15° to +400°F).

Polyurethane: Excellent abrasion resistance and tear-strength qualities make these O-rings ideal for use as dynamic seals in hydraulic and pneumatic application where highly stressed parts are subject to wear. For most maintenance application with petroleum fluids, ozone, and solvents, (except ketones). Polyurethane is not compatible with hot water, brake fluids, acids, or alkalies. Durometer is Shore A: 70; temperature range is -40° to +180°F.

Silicone: Excellent high- and low-temperature capabilities enable silicone O-rings to be used in long-term exposure to dry heat. They perform best in static sealing applications where the O-ring may be in motion. Silicone resists brake fluids and high aniline point oil. It is not recommended for ketones or most petroleum oils. Durometer is Shore A: 70; temperature range is -65° to +450°F.

Teflon: Superior lubricity plus excellent temperature and chemical resistance make these O-rings perfect for static (stationary) sealing applications. For dynamic sealing applications where O-ring may be in motion, Teflon O-rings require mechanical loading. Durometer is Shore D: 55; temperature range is -300° to +450°F.

 

Thank you guys for the info! Bubba

 

I work in a warehouse that my dad runs and the best o-rings you can get are neoprene. DO NOT USE BUNA THEY WILL MELT!!!!!!

 

I use stainless wire cut at different angles on each ends. The engine is a KLX 250 from 1980 stroked and bored to a 340cc with 13 to one compression. Flat copper head gasket with large wire "O" ring.
This engine ran for 10 years before rebuild. Then had a few problems with oil leaks around head.
This 340cc on KLX frame placed in Hill Climbs in the open 300cc to 500cc single or twin class. Built by Jeff Davis of Blue Springs MO.