[Fot] Tappet talk

[Marx Christian tr4-racing]

I want to bring that up again because I have some news about.

I've installed a new cam and tappets last year and now some of the tappets
don't look good and one is damaged.

I had a talk with a famous German cam manufacturer (Schrick) and they say that
tappets should be very slightly domed to handle geometrical imperfections. You
can run flat but it is better to have a dome less than 0.002mm (0.000079").
If the cam has a taper grind then you can have a dome of 0.004mm (0.000157")

The tappets on the market seems to have 0.007mm (0.00275") dome which could be
too much and a cause to cam failures. Depends on the cam if there is a taper
grind on.
So I think the better idea is to grind them flat and give them a slight dome
by hand on a lathe with fine sandpaper....

Cheers
Chris


----- Original Message -----
From: "Bill Babcock" <BillB at bnj.com>
To: "'Larry Young'" <larry.young at pobox.com>; <Fubog1 at aol.com>
Cc: <fot at autox.team.net>; <triumph_marx at freenet.de>
Sent: Saturday, January 07, 2006 2:06 AM
Subject: RE: Tappet talk


> 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 [mailto:larry.young at pobox.com]
> Sent: Friday, January 06, 2006 3:57 PM
> To: Fubog1 at aol.com
> Cc: Bill Babcock; fot at autox.team.net; triumph_marx at freenet.de
> Subject: Re: Tappet talk
>
> Maybe a picture will help.  This is out of a Ford design manual -
> http://home.swbell.net/cartrip/CamTaper2.gif (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).
> Larry
>
>
> >In a message dated 1/6/2006 3:02:04 PM Eastern Standard Time,
> >BillB at bnj.com
> >writes:
> >
> >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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