Surface roughess on valve seats

[HBlom]

Good day, I'm wondering if there are accepted values for seats and if they change for a steel vs bronse seat and froma stainless to Ti valve? I know usually you will have a finer stone to grind the Ti valves than stainless...and assume it's not a bad thing to use the fine stone on the stainless valve. Single point carbide seat cutting would give a very fine Ra, so wondering how this compares to grinding with a stone or diamond or lapping...Has anybody ever put a profilometer on thier valve seats or valve face ?

[Walter R. Malik]

Good day, I'm wondering if there are accepted values for seats and if they change for a steel vs bronse seat and froma stainless to Ti valve? I know usually you will have a finer stone to grind the Ti valves than stainless...and assume it's not a bad thing to use the fine stone on the stainless valve. Single point carbide seat cutting would give a very fine Ra, so wondering how this compares to grinding with a stone or diamond or lapping...Has anybody ever put a profilometer on thier valve seats or valve face ?

A beautiful looking seat from a cutter which is not totally level will not seal as well as a slightly rougher seat from a grinder with a stone.

Being perfectly flat and round are the most important for sealing.

[HBlom]

Good day, I'm wondering if there are accepted values for seats and if they change for a steel vs bronse seat and froma stainless to Ti valve? I know usually you will have a finer stone to grind the Ti valves than stainless...and assume it's not a bad thing to use the fine stone on the stainless valve. Single point carbide seat cutting would give a very fine Ra, so wondering how this compares to grinding with a stone or diamond or lapping...Has anybody ever put a profilometer on thier valve seats or valve face ?

A beautiful looking seat from a cutter which is not totally level will not seal as well as a slightly rougher seat from a grinder with a stone.

Being perfectly flat and round are the most important for sealing.

100% Agree Walter. Flatness and concentricity are key to a good seal with surface finish coming in 3rd. I guess one just wants it as fine a finish as possible, I was just hoping for a number as I'm looking at some diamond honing tools that could cross over as valve seat tools and can choose my grit.

[mag2555]

A pitted concentric seat and or valve will seal until it’s run enough to burn through, a gorgeous new non concentric seat ….well you know!

[HBlom]

A pitted concentric seat and or valve will seal until it’s run enough to burn through, a gorgeous new non concentric seat ….well you know!

It will eventually break the head off the valve as it bends every time it seats in worse case or best case it wears out your guide and valve stem at a prodigeous rate.