Stephenson valve setting

[Bill Shields]

Keith is correct.

You should always set the eccentrics FIRST, then do everything else.

Otherwise you go round and round the mulberry bush...

[jlakes85]

I'm very close now in both directions after un-pinning the eccentrics and setting them separately. Can anyone advise on any guidelines as to how much of a crack the valve should have at TDC? I'm looking to get this dialed in with my set of feeler gauges. Thanks again.

[Soot n' Cinders]

There should be next to no gap if any. It may benefit from a late opening actually, I've been meaning to play with that on my engine but haven't gotten to it yet.

[Brian Hilgert]

Lead

Purpose of Lead: Increasing lead is comparable to advancing the ignition on a petrol engine. With positive lead, the admission occurs before the piston reaches dead centre, thus ensuring that the steam has time to begin applying pressure to the piston as it begins it "power" stroke. High speed steam engines require a long lead whereas low speed freight engines require short or even negative lead. The analogy with petrol engines remains the same.

It depends if you want a "high Speed Shay" or a "Low Speed Shay"

I have a little lead on my engine. Unfortunately, I can't remember how much. I just used the "SWAG" method. (Scientific Wild A$$ Guess). Due to the 2:1 gear ratio and small drivers, the little shay engine would run more than twice as fast as a conventional steamer traveling at the same speed.