Posted by Vaughn on Thursday, January 04, 2007 at 15:05:51 :
First, thanks for the correction regarding lead additive verses lead substitute. I guess you can see I don't use the stuff.
As with hardened valve seats there are hardened valves. Valves that have a face made of stellite are extremely resistant to heat and wear.
Sodium Cooled Valves have hollow stems partly filled with metallic sodium. Sodium melts at 208 degrees F. and at operating temperature it liquefies. As the valve moves up and down, sodium is thrown against the head of the valve to absorb heat, and then gives it up to the cooler part of the stem as it moves down. Sodium valves run as much as 200 degrees cooler than a solid stem valve of the same design.
The general guidelines from all this probably are:
- Under non-extreme conditions you can expect reasonable life from stock valves and seats,
- Use a lead substitute if you like, however if you have coated your gas tank, make darn sure you read the manufacturers label warnings for any chemicals that can damage the coating. Some lead substitutes have those chemicals,
- If you’re having a problem burning exhaust valves, then upgrade to harder parts.
Follow Ups: