[Fot] How many times can you line bore a block?

[Bob Kramer]

I think Chris nailed it. Move it up too much and the timing chain becomes
an issue as well as the input shaft.

A long time ago I bought all the leftover Triumph stuff from a repair shop
that once was a Triumph dealership, which included spare engine cores and
among other things a box of loose bearing caps. There was a block without
caps that was nice otherwise and I decided not to waste it. I was able to
find a set of caps that was close when measured by the fingernail test. For
all I knew they may have been the correct ones but had separated
years earlier. My machinist line bored the block and reported back that the
crank front to back angle was not aligned very well; tilted when compared
to the camshaft bores, and that he had cleaned that up for me. I look back
now and suspect that he was justifying a large bill but who knows. Years
later I still have a couple of core engines I haven't used, stashed away.
The only long term result of saving that block was a thinner wallet. All
this stuff is fixable, including resetting the transmission alignment, if
you want to spend the money.

On a side note, we have also measured blocks where the figure 8
cylinder ledge was off when compared to the deck surface, and I've never
measured a block where the deck and oil pan surface were aligned, so I
don't deck the blocks.


Bob


On Tue, Jul 28, 2026 at 3:08 AM <tr4racing at googlemail.com> wrote:

> Hi Chuck,
>
> the crank is moving upwards from bore action to bore action. Means the
> piston deck is getting closer to the head each time and also the chain gets
> loosen more and more because the crank is moving towards the camshaft.
> A matter of measurement how far you can go.
>
> Cheers
> Chris
>
> -----Original Message-----
> From: Fot <fot-bounces at autox.team.net> On Behalf Of Chuck Gee
> Sent: Tuesday, July 28, 2026 12:20 AM
> To: Philip Gott <vfracing at aol.com>
> Cc: Friends Of Triumph <fot at autox.team.net>
> Subject: Re: [Fot] How many times can you line bore a block?
>
> I could be wrong, but I don’t think line boring affects that dimension.  I
> understand it to be making the caps a little shorter then reboring to match
> the upper diameter in the block.
>
> Otherwise, a bunch of other dimensions would be goofed up too.
>
> Chuck Gee
>
> > On Jul 27, 2026, at 4:56 PM, Philip Gott <vfracing at aol.com> wrote:
> >
> > Or another way to ask the question is “how much misalignment between
> the crankshaft and transmission input shaft can be tolerated?”
> > I had a block completely gone through, including line boring and it ran
> very well until number one cylinder liner suddenly split. The engine hydro
> locked and broke the crank and front main bearing cap. I have a new cap; to
> use it requires the block be line bored again. I’m wondering if anyone else
> has a similar experience and can tell me either that it worked out well, or
> that I should throw the block away.
> > Thanks as always!
> > Phi
> >
> >
> >
> > Sent from my iPhone
> > _______________________________________________
> > fot at autox.team.net
> >
> > http://www.fot-racing.com
> >
> > Donate: http://www.team.net/donate.html
> > Archive: http://autox.team.net/archive http://www.team.net/pipermail/fot
> > Unsubscribe/Manage:
> http://autox.team.net/mailman/options/fot/chasgee22@gmail.com
> >
> >
> _______________________________________________
> fot at autox.team.net
>
> http://www.fot-racing.com
>
> Donate: http://www.team.net/donate.html
> Archive: http://autox.team.net/archive http://www.team.net/pipermail/fot
> Unsubscribe/Manage <http://www.team.net/pipermail/fotUnsubscribe/Manage>:
> http://autox.team.net/mailman/options/fot/tr4racing@googlemail.com
>
>
>
> _______________________________________________
> fot at autox.team.net
>
> http://www.fot-racing.com
>
> Donate: http://www.team.net/donate.html
> Archive: http://autox.team.net/archive http://www.team.net/pipermail/fot
> Unsubscribe/Manage <http://www.team.net/pipermail/fotUnsubscribe/Manage>:
> http://autox.team.net/mailman/options/fot/rkramer56@gmail.com
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/fot/attachments/20260728/66844acf/attachment.htm>