Cam Button

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I'm building a 512 for my 1970 roadrunner. My cam is a hydraulic roller and I added a cam button. Why is it necessary to add a cam button, when the distributor rotates on the cam gear counterclockwise? The counterclockwise rotation should force the cam to the rear of the engine. Someone, please explain why the cam button is necessary?

Walter,
 

ACME A12

Plaid Sport Coat Wearing Moderator
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You don't want it walking too much one direction or the other because of the narrower lobes on a roller and no lobe taper to keep it in place like a flat tappet.
 

V.R.D

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A12 is right the cam can move up to 1/8 inch at varies time in the up and down of rpm range.

if you have ever installed cam barrings then installed the rear plug there is some room there behind the cam
 

Roadtrip

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Hydraulic flat tappet cam lobes are at an angle which forces both the rotation of the lifter and also forces the cam to the rear of the engine.

roller cam will have flat lobes which could allow the cam to walk both forward and rearward
 
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