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RE: Tappet talk

To: "'Larry Young'" <>,
Subject: RE: Tappet talk
From: Bill Babcock <>
Date: Fri, 6 Jan 2006 16:06:39 -0800
Actually, that's pretty much exactly what I said. A dome will help if it
serves to move the contact patch off center. On a TR3/4 engine the cam is
offset from the centerline of the lifter. If you have a domed lifter and an
offset cam it will move the contact patch more towards the centerline of the
lifter, reducing the amount of lifter rotation.  

Note in the picture that the domed lifter does NOTHING to induce rotation by
itself. The first picture showing no rotation has a domed lifter. 

-----Original Message-----
From: Larry Young [] 
Sent: Friday, January 06, 2006 3:57 PM
Cc: Bill Babcock;;
Subject: Re: Tappet talk

Maybe a picture will help.  This is out of a Ford design manual - (do we believe Ford or
Mercedes?). Keep in mind that the figure is greatly exaggerated.  With a 50
to 60 inch radius, the total height of the crown is less than 0.002.  
Lobes in a TR4 engine are offset about 0.050 from the lifter bores.  
(Sorry Chris, all dimensions are in inches).

>In a message dated 1/6/2006 3:02:04 PM Eastern Standard Time, 
>I can't  visualize how doming would help rotation unless it was moving 
>the contact  patch off center in a cam/lifter pair where the cam lobe 
>was centered over  the lifter.

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