I've just spent a few beers looking at some photos of my rockers/valves open and closed
, as I have a similar issue-on the back-burner, but I have Socket-cap adjusters, so maybe different....I'm inclined to agree with Lee, and I'm not so sure that caps will sort it properly, but just be a smooth-over.
Sure they may give more threads on the adjusters, but it won't change the angle that the adjuster strikes the valve tip which I reckon is critical
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As I interpret what Lee suggests, either the lifters need to be longer/higher/less deep pockets, or the pushrods need to be longer (in my case anyway, with ally head a different factor), but we have an agreed stock pushrod length, so the plot thickens...
Edit; I chased up the B31 Valve Cap part, same as A7 Longstroke caps, part # 65-020...not cheap the little buggers, but for properly hardened steel, I'd expect that...one thing to consider as I was looking at my valves is the distance from tip to the collets needs to be more than the depth of the caps, or the thrust will be on the collets- not ideal metinks....