Date: Tue May 3 20:30:30 1994   
Subject: Re: Cam Selection
From: emory!aol.com!shagford

[Because the cam towers are first bolted to the head and then align-
bored during assembly.  The odds of removing a cam tower and reinstalling it
back exactly aligned are pretty remote.  And since the cam rides directly on
the cam tower surface, one can't re-align-bore the head unless one has the
cam bearings built up and ground to a larger diameter. I have had a couple of
instances where my machine shop has unbolted the towers preparatory to
surfacing the head.  I've NEVER gotten a cam to turn as freely as it did
before.  I just can't imagine the nightmare associated with injecting the
shim factor into the equation.

<stuff deleted>  JGD]

uh-oh.  In the process of removing that head bolt I had to remove the cam
towers.  Just how big a problem is this?

Shag

[Hmm, sounds like you have a lot of diddling ahead of you.  You can
get it pretty close but it'll never be perfect.  JGD]

Date: Wed May 4 14:08:00 1994   
Subject: Re: Cam Selection
From: emory!proteon.com!bhaley (Bruce Haley)

>   [Because the cam towers are first bolted to the head and then
>   align-bored during assembly.  The odds of removing a cam tower and
>   reinstalling it back exactly aligned are pretty remote.
   
[even more JGD stuff deleted]

This is one aspect of the Z head I never fully understood, but always
followed regardless (until a head shop did the old "punch one dot in
the first cam tower, two in the second, etc. so we know how to
reassemble them" routine).  It always seemed to me that you could use an
appropriate sized rod (a real "unground" cam, if you will !) to "align"
the towers when bolting them back on.  Of course, if someone could
start casting "new" towers, which could be align-bored, I bet there
would be a good market if alot of our Z heads have had the towers
removed.  Might be a real business opportunity for someone to get in
on the ground floor of the Z car reprodution parts industry (which I
think has alot of future $$$ in it, based on what I see going on in
the Corvette repro parts industry).

Bruce

****************************************************************************
Bruce Haley           * Internet Z-car Club #106 * The VetteNet
Proteon Corp. MS #21  * (2) '71 240Zs            * "World Class Glass,"
9 Technology Drive    * 260Z 2+2 (parting out)   * "Internet Muscle"
Westboro, MA 01581    * 1977 280Z (for sale)     * 1965 327/350 Coupe
bhaley@proteon.com    * z-car@dixie.com(for now!)* vettes@asuvm.inre.asu.edu
****************************************************************************

[It's the same situation as boring the cylinders with a head plate.
Bolting the cam tower on stresses the tower metal and that stress distorts
the bore.  When it is align-bored AFTER bolting, the bore is true in
the stressed metal.  Relaxing the bolt tension lets the bore distort.
It is only luck that will let you torque it back down exactly the 
same way the factory power wrench did.  And if there happened to be
a bit of debris under the tower when it was bolted down the first time,
well.....

Now I HAVE been known to use a cylinder hone to cut half a thou or so 
off a tower to make the cam turn free.  I don't recommend this and 
would NOT do it to a high performance engine but it WILL work to get
a street motor back on the road.

In terms of the machine shop boobs unbolting the towers, I address this
in two manners.  First, I try to stick to the same old shop who knows
what I want.  Secondly I had some bright red anodized tags made up
engraved with the words "DO NOT REMOVE THIS TOWER!"  I bolt these to
each tower using the bolt and hole where the oil gallery goes.  JGD]