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Reproduction Tappets and Clearance

In addition to sufficient tappet shaft to guide block bore clearance, tappets must also have sufficient clearance between the tappet guide skirts.

From the Workshop Manual General Data:

Tappets

Tip radius1.125" ("R" radious)
Tappet diameter.3110 / .3115 in.
Guide block clearance.0005 / .0015 in.

Tappet Guide Blocks

Diameter of bores.3120 / .3125
Outer Diameter1.0000 / .9995 in.
Interference fir in cylinder block.0005 / .0015 in.

Note that no dimensions are given for either tappet landing width or distance between guide block skirts so we must assume that this fit must be arrived at ad hoc.

Looking at the used tappets in the photo below we can see that their dimensions vary considerably. Note that tappet #3 with the greatest dimension between the guide block skirts, not only had the heaviest scuff marks on its sides, it also sustained damage to the cam landing.

Photo of tappets with dimensions

Below: over-sized repro intake tappets purchased in 2024 lacked sufficient clearance to fit between tappet guide block skirts without jamming. It is for this reason that some prefer re-conditioned used tappets over reproductions.

Photo of tappets with insufficient clearance jamming in guide block skirts

An authoritative, trustworthy source says the fit of the hardened tappets can be eased with the use of an oil-stone. In this case I opted to return the over-sized tappets in exchange for ones that fit.

Sources:
Workshop Manual General Data
"New T120R intake tappets not fitting tappet guide blocks", Triumphrat.net.