Cam shimming and lifter rotation.

[CamKing]

lifter taper is also .002

That seems very high. The lifter crown should be between a 52" and 56" radius

[dwilliams]

"Back in the day" there were only a handful of manufacturers that made the cam cores that aftermarket grinders used. The core manufacturers would also provide finished cams, which is why so many companies had street and street/strip cams with identical specifications.

Sometime in the 1990s a batch of bad even-fire Buick V6 cores were sold by one of the manufacturers, which resulted in a rash of cam and lifter problems with aftermarket cams. The lobe spacing on the cores was off a bit. A few guys on the old gnttype.org mailing list managed to track the problem back to the original manufacturer.

Which is all a long-winded lead-up to "if you can't find any other reason, lay the cam alongside a known-good cam and see if all the lobes are lined up the same."

[PackardV8]

Would a smaller radius increase rotation? Our tappet grinder has the chuck holding the tappet on an adjustable plate and can go below 30" radius. Inexpensive operation to regrind the lifters for the radius you think might be better.

[pdq67]

What's the, "installed", spec's of your valve springs? Within the cam's needed spec's?

I mean, not too high over the nose or too low on the base circle here is all..

pdq67