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

To: "Larry Young" <cartravel@pobox.com>, "Scott Janzen" <s.janzen@comcast.net>
Subject: Re: [Fot] Are cam followers truly "flat" for TR6/GT6?
From: "David Talbott" <dtalbott@archrepro.com>
Date: Wed, 6 May 2009 16:06:00 -0700
I think of it as Dead Nuts On or "DNO, Daddy-O" as some have been known to 
mutter.

----- Original Message ----- 
From: "Larry Young" <cartravel@pobox.com>
To: "Scott Janzen" <s.janzen@comcast.net>
Cc: "'Friends of Triumph' Triumph" <fot@autox.team.net>
Sent: Wednesday, May 06, 2009 2:09 PM
Subject: Re: [Fot] Are cam followers truly "flat" for TR6/GT6?


> Oh, you may start something here. We've argued about this in the past (see 
> for example thread - 
> www.team.net/mharc/archives/html/fot/2008-03/msg00206.html).
>
> 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 - 
> http://home.swbell.net/cartrip/LifterGeom.gif
>
> 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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