How many miles for valves to seat?

[Buster]

Just finished fresh rebuild on Harley 45" flathead. Bored 30 over, new pistons/ rings, and 45-degree valve job with new valves which were lapped to seats. Have not started yet but leak down test shows cylinders hold 10 lbs. air when feed 30 lbs. Prior to installing cylinders, I filled interior of each port with gas and no leaks. During leak down test, I can hear some air leakage at intake and exhaust valves. I realize I am loosing a lot of pressure thru unseated rings. Going to run motor and see if valves seat. How long should I run motor (time or miles) to know if they are seated and run leak down test again? I correct that leak down test should not exceed 10-15%? Thanks.

[T. Cotten]

Just finished fresh rebuild on Harley 45" flathead. Bored 30 over, new pistons/ rings, and 45-degree valve job with new valves which were lapped to seats. Have not started yet but leak down test shows cylinders hold 10 lbs. air when feed 30 lbs. Prior to installing cylinders, I filled interior of each port with gas and no leaks. During leak down test, I can hear some air leakage at intake and exhaust valves. I realize I am loosing a lot of pressure thru unseated rings. Going to run motor and see if valves seat. How long should I run motor (time or miles) to know if they are seated and run leak down test again? I correct that leak down test should not exceed 10-15%? Thanks.

Nobody's going to be able to provide empirical numbers, Harry,,

You may be the first!

It is traditional folklore that valves 'beat themselves in", but a precision three-angle cut should limit that to the toolmark; Will that be measureable?
(Interference cuts, where a seat might be a degree off from the valve, should show better effect?)

And Hastings told me modern rings do not "seat", and if the park'ing or other coating was worn from the face, it was worn out. Blow by would be through the ring gaps, and I listen at the timing hole.

Looking forward to your data!

....Cotten