Convex? Or flat? It’s rumored that the tappets had rounded bottoms so they would rotate.
But…I’ve got a box of NOS ‘54-‘55 261 tappets here in the shop and they’re as flat as flat
can be. Checked the original ones that came out of my ’59 261 on the surface plate and
guess what…..the faces are as flat as a Pugs puss.
http://www.pbase.com/dennygraham/image/161876786 Another way that an engine designer can rotate a lifter is by offsetting the lifter bore
centerline to the cam lobe. And if you look at the alignment of the lifter bores to the cam
lobes in this 261, some are offset….and some are not. Tapered cam lobe is another feature
used by some designers and in this engine, some of the lobes are tapered about
.004”……and…..some are not.
I don’t have any idea where you would find the specs on the cam and lifter design for these
engines to see what method was used, but it would be interesting to know. The taper
required in some cases is so slight it’s difficult to tell if it’s taper you’re measuring or just
normal wear. And, Vintage engines had flat cams, flat tappets, tapered cams, convex
tappets, and offset bores. Nothing cut in stone and every designer had his own idea of how
to get the most life out of the cam and lifters.
DG
