Modern Valves and Guides

P

pbishop

Senior Member
My standard valves and guides (adjustable push rods) have worked perfectly over the years and I generally go by 'if it ain't broke then don't . . . .Still, I was wondering what the advantage might be with the modern ones?
 
The modern tappets are adjustable, as opposed to originals which were not adjustable. With original tappets, the bottom end of the valve is progressively ground down until the correct valve to tappet clearance is attained. This is both time consuming and tricky, in that, if you grind too much off the valve, you can't put the ground off material back on the valve and it will either have to be used in another location on the engine or scrapped.
 
They cost less to manufacture than mushroom stem
They weigh more than stock
the stem is larger so it can better obstruct the flow
Once the guides are in a machine shop can use their 'normal" tooling instead of having special pilot for A --and are more likely able to understand how to work on them ----I have gotten calls "how do you get the valve out???" with stock mushroom stems
 
Kurt, the biggest two issues I have with original-style valves is the composition of the original valve, and the two-piece guide. Even with NOS Ford two-piece guides, you can have wear that causes a valve to burn. When was the last time you heard of a stainless Model-A valve with a one-piece guide that burned?
 
Stem clearance is much better with a straight guide. Years ago I bought new split guides and they were so bad I re-used the old ones. So as Brent says, valves will last much longer with modern guides, and the few thousands bigger stem won't affect power enough to notice, probably not even on a dyno.
 
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