Cam regrinds feasible? (roller regrind)

[Howard Wilkinson]

Jack:
    I have long suspected that many cams have considerable error in
the alignment of lobe centers.
    I once was asked to change out the third Subaru (EA 81) engine for
a fellow who had installed 2 rebuilt engines only to have to return
them to the rebuilder due to rattling.  This was a major Seattle area
rebuilder.  When I looked at the engine pior to removal to determine
exactly what was happening, I discovered that it was valve noise, but
that it couldn't be adjusted out of it.  This seemed odd to me, so I
took measurements with feeler guages while turning the engine over a
little at a time, an discovered a low spot right at the base of the
ramp which when proper adjustment was made opposite the lobe yielded a
measurement of about .025.
    Human error seem to be inescapable.  Unfortunately with camshafts
it is very difficult to verify that they are what they are supposed to
be.     H.W.

-----Original Message-----
From: goflo at pacbell.net <goflo at pacbell.net>
To: diy_efi at efi332.eng.ohio-state.edu
<diy_efi at efi332.eng.ohio-state.edu>
Date: Sunday, May 02, 1999 2:39 AM
Subject: Re: Cam regrinds feasible? (roller regrind)


>An additional consideration with re-grinding cams is the
>torsional relaxation caused by removing significant amounts
>of metal. This changes the phase relationships between lobes.
>I have in my possession a performance regrind TR6 cam which
>has a 14 degree phase error between front and rear lobe pair
>centers. The grind was done by a national rep grinder (and
>purportedly checked with their cam doctor).
>
>This is probably a worst-case deal, as this cam is long and
>slender, and has ~.125" additional lift ground-in, but much
>smaller phase errors screw things up noticeably.
>This too can be avoided by proper regrinding techniques, but
>once again, by the time you do it right, you coulda bought a
>new one...
>
>I check new ones too :)
>
>Regards, Jack
>
>
>