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Re: [Fot] Are cam followers truly "flat" for TR6/GT6?

To: Scott Janzen <>
Subject: Re: [Fot] Are cam followers truly "flat" for TR6/GT6?
From: Larry Young <>
Date: Wed, 06 May 2009 16:09:18 -0500
Oh, you may start something here. We've argued about this in the past 
(see for example thread -

What is dead flat?  Most lifters have a very slight crown.  Usually, 50 
to 100 inch radius of curvature, which is about 0.001 to 0.002 in across 
the lifter.  The reason for this is to insure that the lifter does not 
contact the side edge of the cam. e.g. due to misalignment or cock of 
the lifter in the bore.  Some people might call this dead flat.

Most camshaft lobes are also tapered.  The reason for this is to promote 
rotation of the lifter.  The lobe taper must be matched to the offset of 
the lifter bores relative to the cam lobes.

Here is a picture of the usual arrangement -

If your lobes are not tapered, you should be able to run flat lifters as 
long as your alignment is dead nuts (love that machinist lingo). I would 
run lifters with a slight crown.

And now we should be hearing from Bill Babcock and Chris Marx.

Larry Young

Scott Janzen wrote:
> The lifters I am about to put into a GT6 engine to go with a new cam,  
> tested, ground and polished by a well known source, are not truly  
> flat.  If I put any two face to face, I can rock them slightly, almost  
> imperceptibly, so they seem to be ground with a radius.
> The set I have from another engine, used one short season, also  
> reground through the same source, do not rock when put to the same  
> test.  Can't us these because they were run with a different cam.
> Do I need to find another set of lifters to replace the recently  
> reground ones with the radius?  The cam source tells me they should be  
> dead flat, and that the lobes on the cam have no taper.
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