Need help from the flathead gurus...? Valve clearance issue

[GOSFAST]

Originally Posted by scooder

I'm not saying that the radius is not necessary, it is ideally perfect. Just saying that flat lifters have been used for years in engines rebuilt using genuine NOS Ford lifters.

Martin.

Hi Martin, one of the issues that I would foresee affecting the flat-faced lifters is the final spring pressures. I'm sure with any new factory-built units with spring pressures in the 40# range there would not be an immediate issue, when you get up into "performance-oriented" spring pressures I suspect that time-frame would be shortened considerably?

I do believe that is excellent info from Ron out at Isky! And I'm certain Isky and most other cam vendors buy from Paul at "Hy-lift-Johnson", I know for a fact Comp Cams is one company that uses their lifters. Its the same company we use when we need add'l supplies! All the new cam blanks are likely from CMC (Camshaft Machine Co) and are tapered??

It is also my strong belief (due to the Flathead design with the valve riding directly on the lifters, lacking pushrods/rocker arms) that the radiused face plays a part in causing the valve to "rotate" some, which is also why I don't believe you need an alternate "valve-rotator" type retainer on the topside to be used. I can't prove any of this but it does make perfect sense to me. Remember, the opening/closing spring action also helps some with valve rotation.

Thanks, Gary in N.Y.

P.S. In all my years of machining/building units, the old "Nailhead" Buicks were the ONLY ones I ever HEARD of having non-radiused lifter bottoms, and I'm not certain about this either, I have never seen any that way.