1/4 Galloway valve question

[blockmanjohn]

Hi, the plans call for the valve seat to be cut at 41 degrees and the valve itself to be cut at 45 degrees. I'm
not sure why this would be better than cutting them both at 45 degrees. Do they have to be lapped together?
Also, I plan on using 12L14 for the valve. Is this a good choice. This is my first real IC engine and I hope this isn't a dumb question. Thanks in advance, John.

 

[Cogsy]

Valves are often cut at a slightly different angle to the seat to minimise contact area for a better seal, though it's usually given as 1 degree difference rather than 4 degrees. Mostly (as far as I know) for models the same angle is used and they seal fine. You will need to lap them together but you do want a small seal area, not full width of the valve face, to maximise sealing pressure.

 

[Jasonb]

Are you working from the old Shelley drawings as I think they show the 41/45, I built the 1/3rd scale to George Britnell's drawings and that has them both at 45deg. Also used stainless steel 303 for the valves as I usually do.