1mm oversize valves

[bentvalves]

good-day fellas.

What are some of your thoughts on oversize valves that put the 45* seat angle smack dab at the very outside diameter of the seat insert in aluminum heads. This requires the top cut of anywhere from 15-30* to be machined into the combustion chamber and depending on the chamber shape, seems counter productive. Having the seat angle at the very O.D. of the seat seems retarded to me as well, but maybe I'm just retarded.

[modok]

If the valves are too big for the seats, you certainly have the option to make them smaller, any amount you want.
It is much more difficult to make them bigger.

Some heads can take 1mm bigger, some can't. Sometimes it's very handy to make up for misalignment from changing the guides, IF the throat was rather large to start.
An exhaust valve with the valve as big as the insert......I can't think of any case that would be good, the seat would be too thin, or throat too large. And not great on the intake either with PM seats, sharp edges could chip, but with cast or ductile seats, maybe ok

[Frankshaft]

I know what your saying op, I personally don't like maxing out the valve size on a given seat ring, I like to have some top cut on the seat ring. If all the top cut is in the chamber,I don't care for that. Then you end up hogging to much of the seat ring out to size the throat for the bigger valve. And there isn't much seat ring left and it can move around and or fall out easier if it gets over heated