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#597533
Wed Dec 02 2009 03:27 PM
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Joined: Dec 2008
Posts: 1,840
OP
'Bolter
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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?
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Joined: Feb 2000
Posts: 4,593
'Bolter
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I would bet all lifters and cams are ground the same. With out any rotation, the cams don't last any time at all.
Joe
Last edited by Joe H; Thu Dec 03 2009 04:47 PM.
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Joined: Dec 2003
Posts: 2,736
Shop Shark
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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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Joined: Feb 2004
Posts: 25,700
Kettle Custodian (pot stirrer)
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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.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!"
Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.
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Joined: Dec 2008
Posts: 1,840
OP
'Bolter
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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?
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Joined: Dec 2008
Posts: 1,840
OP
'Bolter
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Thanks - I just assumed it was a typo!
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