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Can a hardened valve seat lose hardness?

B

blue_tractor_man

Member
I am working on my 1967 Kohler 4 cylinder L600 flathead generator. I am in the process of restoring the valve seats with Neway carbide cutters. This is a Craigs list purchase. I was told that the engine had set up inside their garage for 15 years after being removed from a motor home. I cannot tell for sure, but it seems that the #4 exhaust valve seat insert seems a little softer than the other three. Not scientific, but the material seems to be coming off faster than the other three. There are signs that the engine ran hot, such as a warped head, and the exhaust valves had rings pounded, worn, or eroded on their faces.

This is an 1800 RPM, 6.5/1 compression ratio engine designed for leaded gas.

How can I tell if this is happening? Does it make any difference? Can these valve seat inserts lose hardness? Is the hardness all of the way through the insert, or just the surface?
 
Are sure that it has valve seat inserts at every valve? There were a lot of engines in that era that were factory built without inserts. I've not seen inserts lose their hardness, but have seen engines that have had inserts installed only where the original cast seat was no longer serviceable.
 
Anything hardened by heat can be softened the same way. Course it could be one seat wasn't hardened the same from the get go.
 
Manufactures components are dimensioned with a tolerance on every measurable dimension. Anything within that tolerance range will deliver acceptable performance and durability. It's possible that one of the valve seats was made at the lower end of the acceptable hardness range and the other three are from a different batch that are closer to the high range of thee acceptable hardness range. All four seats delivered much more than the (20 year?) life the engine was designed for.
 
Do you know if a L654(next model newer than yours) has any parts compatibility. I have a L654 i am going to scrap. The head gasket went And I don't want to put any more money into it.
 
It does really depend on the seat material.

As has been said some seats are parent metal, some hardened steel, some are bronze, and a few are stellite which is pretty hard from beginning to end. Heat usually does not soften stellite. That is why they used to line machine gun barrels with it.
 
Possibly that seat has been replaced before, or it may be an original and the others have been replaced.

I don't think it has been hot enough to soften the seat. If that happened the seat would be loose, other damage as well. That would be something worth checking tough, be sure it is not loose

What is your intended use?

Will it be run long hours under heavy load? If so, it might be worth replacing the seats now while you're in there.

If it will have an easy life, it will probably be OK.
 
I think most all of the parts except crank and rods are the same. The L654 had a slightly longer stroke. I would be interested in your generator if you are anywhere close, or close to somewhere that I will be going. I am in Memphis.
 
The engine will be used very little. Old engines are just a hobby, and I will run it some as a backup generator. The four exhaust seats have inserts and the intakes are just cut in the block. It came that way from the factory.
 
may have not been hardened to start with, i just bought a new chain for my chainsaw, some of the teeth are so hard you cant file them others are a little soft. china must be having trouble with there heat treat....
 
Valve seat inserts range from whatever the OEM used to Stellite seats that may have been installed later and are harder than $&%#.

WHY are you hacking away at the valves seats vs. having a pro touch them up with a stone which would most likely remove a LOT less material than what you are trying to do?
 
That happened a lot with the old ZipPenn chains (made in USA) we used to buy cheap back in the '70s. A sign of faulty manufacturing in any country.
 
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