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It is not difficult to straighten cams yourself. You can do it with a
blunt cold chisel and hammer, but I prefer to use an air hammer with a
blunt rounded chisel. Use V blocks and a dial indicator to check it and
decide where it is bent. You hit the cam between the lobes, which
relieves the stresses and causes it to curve up. It seems counter
intuitive, but that is the way they bend. It has been a while since I've
done it, but I believe that is how it's done with these cast iron
blanks. If it still doesn't fit, then have it ground to fit as Greg
suggested.
- Larry Young
On 1/5/2015 8:40 PM, Scott Janzen via Fot wrote:
> I've got a bit of cam bind in a new cam I'm installing in the GT6. It
> appears to be a combination of slight run-out (i.e., the cam is
> slightly bent, 1/1000 of runout in the middle), journal size right at
> the factory maximum spec, and installed bearing I.D. that is at or
> below the factory minimum I.D.
>
> It's also possible that the block is not bored perfectly straight as
> the binding is not consistent around the rotation, but another cam I
> have, with journal diameters 5/10,000 smaller, turns freely. I have
> not checked that cam for run-out.
>
> Question is, is there a tool to "expand" the bearings into the block
> and possibly gain a bit of clearance? I'm told the factory manual for
> one of those Octagon cars calls for such a tool. I'm using the
> typical Spitfire bearings.
>
> Next stop is a machine shop with a crank straightening machine to see
> if they can use it to straighten a cam.
>
>
>
>
>
>
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>
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>
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It is not difficult to straighten cams yourself. You can do it with
a blunt cold chisel and hammer, but I prefer to use an air hammer
with a blunt rounded chisel. Use V blocks and a dial indicator to
check it and decide where it is bent. You hit the cam between the
lobes, which relieves the stresses and causes it to curve up. It
seems counter intuitive, but that is the way they bend. It has been
a while since I've done it, but I believe that is how it's done with
these cast iron blanks. If it still doesn't fit, then have it
ground to fit as Greg suggested.<br>
- Larry Young<br>
<br>
<div class="moz-cite-prefix">On 1/5/2015 8:40 PM, Scott Janzen via
Fot wrote:<br>
</div>
<blockquote cite="mid:775BAF52-B61C-4DA5-B7E0-DB2F6A0D34BA@me.com"
type="cite">I've got a bit of cam bind in a new cam I'm installing
in the GT6. It appears to be a combination of slight run-out
(i.e., the cam is slightly bent, 1/1000 of runout in the middle),
journal size right at the factory maximum spec, and installed
bearing I.D. that is at or below the factory minimum I.D.
<div><br>
</div>
<div>It's also possible that the block is not bored perfectly
straight as the binding is not consistent around the rotation,
but another cam I have, with journal diameters 5/10,000 smaller,
turns freely. I have not checked that cam for run-out.<br>
<div><br>
</div>
<div>Question is, is there a tool to "expand" the bearings into
the block and possibly gain a bit of clearance? I'm told the
factory manual for one of those Octagon cars calls for such a
tool. I'm using the typical Spitfire bearings.</div>
<div><br>
</div>
<div>Next stop is a machine shop with a crank straightening
machine to see if they can use it to straighten a cam.</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
</div>
<br>
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