If you do not have shims it may not be a problem. In the days when
production tolerances were not as good as today shims were used to adjust
bearing clearances. With Chevrolet, this carried over to the days of insert
bearings. It would be preferable to have the block line-bored and have the
rods straightened and rebored and to have the crank straightened as well
as ground. Presumably, your crank grinder ground the mains to be
concentric, but you never know.
In any case, you can adjust the bearings for greater clearance with shims
under the caps or adjust them for less clearance with tapered shims behing
the inserts. Use "Plastigage" to determine the clearance. Once the crank is
installed with the main caps torqued to spec and with the specified
clearance in each bearing, but no rear main seal installed, the crank must
spin free. If it doesn't, either the block needs align-boring or the crank
needs straightening.
While you've got it apart you should balance it. These ol trucks have
mounts that transmit more vibration than one might like. Buy a triple beam
balance from a local scientific supply or where ever the school science
dept. buys them and weigh everything. It sounds like a lot of trouble but
its worth it in the end. After you get the pistons and rods to weigh the
same, you can tell the machine shop how much the big ends weigh and they
can dynamically balance the crank. Have them do the flywheel and clutch
cover too while you're at it.
-Tom Allen
51 3800
At 10:26 PM 8/17/99 -0700, Antonio R. Tijerino wrote:
>I have a question for the engine rebuilding experts. I am getting a '56
>235 cid engine that has been recently bored 0.30 and the crank has been
>ground 0.10/0.10. New cam bearings installed. I have read the 6 part
>engine rebuilding article posted on the oletrucks list and does not
>mention anything about the main crank bearings "shims". I took the block
>to the machine shop and the machine shop guy told me that installing the
>"shims" was a job on itself and that it make the price of putting the
>engine together more expensive. Can anyone tell me more about these
>shims, how to install them and what is the story? is this guy trying to
>pull my leg? can I install the shims myself?
>
>Thanks,
>
>Antonio,
>'53 3100
>
>oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
Tom Allen
Seattle, WA
oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
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