> I was talking to a mechanic friend of mine yesterday about
> the rebuild work on the TR motor. When I told him the crank was a
> replacement he suggested there may be problems with fitting this to
> another engine and perhaps the rods need to be line bored to match
> the rods. Anyone throw light on this process, and do I really need to
> take it on board.
As Tom has already written, line boring refers to boring the cam and crank
bearing openings in the block, to be sure they are aligned with each other.
The rods do not have to be aligned with each other, thus there is no sense
in line-boring rods.
Line boring is expensive, and in the case of cam bearings means you have to
use special cam bearing inserts (assuming you aren't starting with a very
early engine that was not bored for inserts at the factory). The factory
line bored the blocks when they were made, and it's very unusual for one to
warp enough to need boring again.
Your mechanic friend may have been referring to having the rod ends sized
and checked for twist, which is recommended by the factory manual (although
it has nothing whatever to do with changing the crankshaft). But, I've
never done it, and I've never seen any indication that my engines needed it
done. The symptoms would be bearing inserts or pistons that are worn more
on opposing corners.
I've never heard of any problems with interchanging cranks between engines.
The factory did not select cranks to fit particular engines. Cranks can be
bent of course, it's definitely worth double-checking when assembling the
engine (put Plastigage in all 3 mains, torque all 3 caps, check for tight
spots; then turn crank 90 degrees and repeat) but normally the shop that
grinds the journals will check for straightness and throw alignment.
Randall
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