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RE: TR3 engine rebuild (holed piston)

To: <triumphs@autox.team.net>
Subject: RE: TR3 engine rebuild (holed piston)
From: "Randall" <tr3driver@comcast.net>
Date: Thu, 9 Mar 2006 17:43:50 -0800
> My question to the list is, can I just pull the pistons and liners (got a
> trap-door pit in my garage that allows easy under-car access) and
> pop in this
> big bore kit...or should I pull the motor and change out the
> mains and all the
> rest of it, a full rebuild.

No doubt this will be a minority opinion ... if the crank journals are in
decent shape then I would just change the main & rod bearings in-situ and
not worry about the cam bearings.  Pull and inspect the oil pump, of course,
and clean up as much as you can.

>  I'm also wondering where all those pieces of the piston top wound
> up...and I figure the answer can't be good...

Should be mostly in the oil pan.  To get to the cam bearings, they have to
first go through the oil screen, then the pump, then through the main
bearings.  If any big chunks got into the main bearings, then the crank
journals will be ruined and you'll have to pull the motor.  But anything
small enough to make it through both the oil pump & main bearings will
probably not do any catastrophic damage to the cam bearings.  After all, the
pistons are aluminum and so are many modern bearing inserts.

Before everyone tells me how crazy I am, I did exactly this to a TR3A motor
that had not only holed a piston (by dropping a valve), but also broke the
liner to pieces and bent the rod.  I swapped the head, pistons, liners & 1
rod during winter break in college (outdoors laying in the snow with a
heater under the car).  That engine still runs today !  (Granted, it's
probably only covered 20k miles or so since then, spent most of it's time
sitting in Dad's garage after I bought my own TR3A, but still AFAIK it's
never had the head off since 1974.)

Has anyone ever heard of a TRactor motor spinning a cam bearing ?

Randall


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