On Wed, 9 Mar 2005, Charly Mitchel wrote:
> Allen, The Spitfire cam bearings will fit with a little boring of the block.
> I was told to do the same and I went to my machine shop and he could see any
> reason to change. We may find differently form the other members, but If
> there isn't any damage, why change it? Is it better with Spitfire bearings?
While there is always merit to the philosophy of "if it ain't broke, don't
fix it", the TR6 cam bearing surface is one aspect of the TR6 motor that
is weak at best.
The problem is that if you are racing a TR6, you're by definition running
higher revs and all that stuff. The stresses on the cam are significant
and in the absence of "proper" bearings in the block, you will experience
either reduced oil pressure (when one or more cam bearing surfaces oval
out), a broken cam (either due to siezing or from flex) or other
calamities. If you run higher than stock lift cams, you are further
increasing the stresses on the cam.
Nothing is free, but installing cam bearings on a race TR6 motor is good
insurance.
Note that it apears to be critical to measure the bearing clearance on the
cam bearings after install and that you need to hone to the proper
dimensions of _your cam_ to get everything right. This is documented at
the APT web site, www.aptfast.com and they have a tool that you can use to
"hone" the bearings.
> Charly
regards,
rml
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