A couple of thoughts about regrinding camshafts (I know the question was about
regrinding lifters, but it seems like a good time to throw this in).
First, it takes a quality shop to do it right. They create a master of the cam
lobe
and use that to grind the cam. They don't make a master of the whole cam, just
the
intake and exhaust profiles. Then they grind the cam lobes down, reducing the
base
circle diameter until they can fit the correct profile into the existing
material on
the cam. A couple of bad things can possibly happen during this process, if the
machine shop isn't careful. One is that the masters can become worn over time
and
will no longer correctly reproduce the original profile. Another is that they
might
not get the lobes aligned exactly, causing the cam timing to be either advanced
or
retarded from the design specs. Worse yet, the individual lobes may not all be
aligned the same, making for a very strange cam.
Yes, the cam will have to be re-hardened afterwards, or else the lobes will go
away
in a hurry. This should be a no-brainer for any decent shop, but it doesn't
hurt to
ask just to make sure. If they weren't going to re-harden it unless you
specifically
requested it, take it somewhere else. The same is true for lifters or rockers.
One issue for an OHC engine (U20) is that reducing the base circle diameter on
the
cam will retard the cam timing slightly. For the average street motor this
probably
is no big deal, but if you are building something other than a grocery-getter,
it
could be. The L-series engines have different thickness lash pads available for
making such precise adjustments, but there aren't any for the U20. A pushrod
motor
like the R16 is not affected by base circle diameter.
Jim Tyler wrote:
> uuuuH, it's OK,,,, if you aren't hoping for a bazillion miles, and are
> going to keep the revs down for street use yea, ok.
>
> If you are blueprinting, forget it.
>
> Lifter/cam metalurgy is a major issue for R and A engines when racing.
> The stock stuff is really not tough enough. For street, with stock springs,
> new OE are fine., refaced are just ok.
>
> Coated versions help with proper break in, but once you get through
> the coating you are into the soft stuff and all bets are off.
>
> Jim Tyler
>
> ----------
> From: Toby B[SMTP:toby@wolfenet.com]
> Sent: Friday, October 08, 1999 10:30 PM
> To: a roadster list
> Subject: Re: camshaft
>
> In a 1600,
> Is it kosher to resurface the lifters? Is there enough hardness to
> 'em? Years back (7) I had mine done, and the cam reground. So far it
> seems to be holding up alright, but I havn't measured the lift recently,
> either... I HAVE been wrasslin' with noisy rockers (well, OK, checking
> the adjustment every 500 miles, to discover that they're adjusted
> correctly) in the vain hope that they'll SHUT UP! One of these days,
> I'll get a new rocker shaft assembly...
> Toby
>
> Philip Erickson wrote:
> >
> > Either way you go with the cam, have your lifters resurfaced. Most lifters
>are
> > convex when new and wear along with the cam. A quick and dirty way you can
> > check for wear is by placing the two bottoms together and making sure they
> > "rock".
--
Gordon Glasgow
Renton, WA
http://www.gordon-glasgow.org
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