OK, my ONAN engine in the Mity Mack scid steer has lost power to the
point it is clear it is only working on one cylinder.
So I find that one of the intake valves has an insert that fell out
after pulling out the valve. There was 0.030 inches of slop between
the OD of the insert and the bore of the aluminum block where it
existed.
OK I can bore out the block.

What rockwell hardness should the new insert have? The valve was Rc
45. I would think the seat should be in the same range.

Anyone here have a knowledgeable value for what the Rc hardness should
be for valve seats.

Searching google gets patents to sintered processes,. but no stated
value. Ratz!

ignator

PS. Onan no longer supports this 1972 engine. It's a NTC engine, it
may be time to put a new engine in it that is maintainable.

I machined a replacement insert from O2 round stock, currently at Rc
20, will this last a few years without hardening? If I harden it, Rc
55 is around it's peak before tempering, how far down should this be
drawn for a reliable hardness?

Thanks to you engine experts for input.