Cam regrind question

[Flyingpiper59]

Good morning Chums!

I need some help to understand a concept or two……so… a tale of two camshaft re-grinds…. I had my original camshaft to re-ground to a stock 250……. and purchased a second 270 regrind from a very reputable parts supplier….. I want to say this at the outset I KNOW that the 270 grind has a 270 lift…. What I don’t understand is the how of it?…. for example, the 250 regrind lobes are larger in every measurement than the reground 270….. 250 grind still has plenty of Cam lobe at the heel and extends past the camshaft diameter….. The 270 grind is undercut….. Can one of you engineering marvels explain this mystery to me I just can’t wrap my head around it?…. how does considerably smaller equate to the higher lift…..PFM?……many thanks in advance.

Cheers! Ed

[Jerry VanOoteghem]

Ed,

Lift is simply the difference between the base diameter measurement and the overall height of the cam lobe. If your cam lobe height is about the same for each cam, but your base diameter is smaller for the .270, the difference between the two dimensions will be greater for the .270, hence, greater lift. By the way, a measured .270 lift on a cam will only net you about a .260 actual lift on the valve, due to having to subtract your valve lash measurement.

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[Flyingpiper59]

Thanks Jerry!

[Art M]

There is more to the story on .270 regrind profile. The the duration and hence the overlap increases with .270 lift and its effects as explained by Glen Chadfin a few years ago.

Also I wonder how deep the case hardening is on original camshafts.

But ar this time, I guess regrinds are the only thing that is available for rebuilding engines.

Art Mirtes