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« on: January 31, 2015, 01:47:13 PM »
FYI the lobes on a mech flat and hyd flat tappet are ground on a slight taper. Approx. .0025 when new. The flat lifters are ground on an approx 32 in Radius.On a V-8 8 lobes are ground with the taper in one direction and the othere 8 are taper ground in the opposite direction to help offset cam walk forward or rearward. There is also as problem with lifter bores being 90 degs to the cam C/L forward to rearward. [note: Isky has a way to garage test your block-see their web site] With a Roller cam, Lifters being out of Square front to rear will cause EDGE RIDING of the roller wheel and bearing failures in the roller lifter. Lifter bore missalignment ONLY from left to right as viewed from the front or rear of the block will cause cam timing issues [ie when degreeing the cam per the card. I do #1 and #6 as TDC should be the same for both cyls] The interface action between the tapered lobes and the spherical lifter bottoms causes the lifters to spin in their bores when unloaded. This action prevents the lifters and lobes from contact in the SAME pattern. The non-additive oils [mandated by EPA to keep the Cat Conv Operating] has caused most of the Wipe-outs. The current OEM Roller cams and lifters dont require these additives[ However most quality Race ONLY oils contain These Additives in a much High PPM than ever in the older oils/ These additives also help with Ring breakin and engine life]. As to End-Play on Racing roller cams-YES it must be controlled. I try to hold to .005 with a roller type thrust brg. Sprockets with no Brg. running against the block face can use .008 max. A little trick is to scrape a Tiny groove from the #1 CAM bearing feed hole [in the babbit] to the front end of the #1 cam brg., so as to lube the sprocket/block face area. Hope this helps you Al