Is there any correlation? Or, I presume, more a factor of the rocker geometry? Perhaps just fitting the middle 3rd of the valves length? Side load on the valve?

(These will be rough numbers from memory)
My old engine has 49 and 55mm guides (120mm valves). I will/would be using B series exhaust guides at about 47.5mm (with 100mm valves), but D series valve guides are also 47.5 with the same long valves.
My install height is 15.5mm. 2.5-3 more than the B, but actually less than the D.

So the question then is, does any experienced builder here think the shorter guide with the old 80's rocker arm design will be an issue? How thick is a B spring seat?
And to add on, would a 37mm head valve with a 5.5 stem be a potential issue?



If I need to clarify with more pictures then tell me none of that made any sense...