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#597533 Wed Dec 02 2009 03:27 PM
Joined: Dec 2008
Posts: 1,840
panic Offline OP
Different manufacturers have used several method of reducing cam lobe and lifter wear, typically by inducing tappet rotation.
The most common method is a tapered lobe and a crowned (very large radius) tappet contact surface.
Does anyone know what method was used on the 235?

panic #597552 Wed Dec 02 2009 05:30 PM
Joined: Feb 2000
Posts: 4,593
I would bet all lifters and cams are ground the same. With out any rotation, the cams don't last any time at all.


Last edited by Joe H; Thu Dec 03 2009 04:47 PM.
Joe H #597576 Wed Dec 02 2009 07:03 PM
Joined: Dec 2003
Posts: 2,736
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Lifters must rotate, otherwise how do you explain the uniform concave wear often observed on them?

Hotrod Lincoln: I hope you weigh in on this as you know a lot more about it than I do.

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53moneypit #597581 Wed Dec 02 2009 07:14 PM
Joined: Feb 2004
Posts: 25,700
Kettle Custodian (pot stirrer)
The most common method to induce lifter rotation is to put a slight radius on the lifter bottom, and slightly offset the lifter centerline in relation to the cam lobe centerline. As the lifter is taking up the slack caused by clearance on a solid lifter cam, or the lightly-loaded acceleration ramp portion of a zero-clearance hydraulic lifter, the wiping action of the lobe on the off-centered lifter spins it. Only roller lifters are designed not to spin in their bores. Lifters that are worn flat on the bottom are worn out. Concave lifters are definitely junk! A straightedge held across the bottom of a good lifter should rock slightly. Also, NEVER swap lifters to another lobe of a camshaft, or put them onto a different cam, once they've established a running fit on a particular lobe. The advice about running-in a new cam for 20 minutes at a fast idle is to provide enough splash lubrication to the cam and lifters to prevent scuffing while they're breaking in.

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Hotrod Lincoln #597721 Thu Dec 03 2009 02:21 AM
Joined: Dec 2008
Posts: 1,840
panic Offline OP
I agree, inducing rotation is the goal.
But... not all cam lobes are tapered. In some engines, the tappet offset must match the taper direction.
It appears that the 235 lobe is way narrower than the .990" tappet, and the tappet is offset almost to the centerline, but I can't find any data re tapered or not?

panic #597937 Thu Dec 03 2009 05:00 PM
Joined: Feb 2000
Posts: 4,593
I went back and edited my post, I ment to say with OUT any rotation, the cams will wear.

Here is a link from the Hamb site, kinda interesting opinions!


Joe H #597978 Thu Dec 03 2009 08:11 PM
Joined: Dec 2008
Posts: 1,840
panic Offline OP
Thanks - I just assumed it was a typo!

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