Joe:
To answer that question, a couple of questions need to be
considered first.
1. Are the cam journals in good shape? Are they scored, out of
round, other otherwise mangled? If so, then you will need to line bore
and install cam bearings, simply to restore correct functionality to
your motor.
2. If the journals are in good shape, are you running
competition valve springs with a rally/sprint or race cam? If so, the
valve springs demanded by that type of cam will increase the loadings on
the cam journals and will require bearings. A mild street cam with stock
or near stock valve springs will not be a problem. But the wilder you go
on your cam shaft, the more cam bearings make sense.
When I rebuilt my motor, the cam journals were in perfect
condition after 70,000 miles, so I didn't bother. There was no scoring
or wear in evidence. The cam itself had journals that were perfect as
well (although one of the lobes was ground flat, but that is another
story). My cam is a 270/272 cam with almost stock idle, and TR6 PI valve
springs. Based on what the factory did, I would say you only need
bearings if your cam is in excess of 280 degrees.
You should be aware, however, that this is from a guy who
decided not to go with hardened valve seats either, so I am a bit of a
cowboy.
YMMV.
Vance
1974-1/2 Momosa yellow TR6.
http://home.comcast.net/~v.navarrette/
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Lizirbydavis@cs.com
Sent: Saturday, October 02, 2004 6:07 PM
To: 6pack@autox.team.net
Subject: are cam bearings necessary?
I find myself in need of a short engine rebuild. As much as the idea of
building a "high performance engine" appeals to me, the sad truth is
that I
rarely have an opportunity to drive hard. I like to accelerate fast as
much as
anyone, but I rarely shift over 5000 rpms. Most of the time I'm driving
sustained 2500-3000 rpms. Currently I'm running 9.0:1 compression,
Strombergs, a
mildly ported head with headers, Falcon dual exhaust and a mild cam
(unknown
specs.) For the most part I'm satisfied with the performance of the
engine,
although I'd enjoy a little more torque. The head is new, the carbs and
ignition
are up to snuff, but the bottom end is sick. What cost efficient (what
ever
that means) improvements can I make to increase performance, reliability
and
longevity? Again, the idea of a wild cam, expensive induction changes
and
bullet proof components are exciting, but the fact is I mostly drive the
car to
work and on club outings, some of which are pretty long. I've heard
that street
motors really don't need cam bearings. I've priced the machine work for
this...ouch! Is it really worth it? Any ideas for a guy with $2500.00
to spend on
a motor?
Joe Davis
Check out the new British Cars Forum:
http://www.team.net/the-local/tiki-view_forum.php?forumId=8
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