Absolutely you cannot bore a 260 to 289 specification. .060 is not reccomended
but I have built a dozen or so over the years and not had a problem. .030 is
great if you have a standard bore block to start with. Again...boring to 2/10
of an inch is ludicrous...
Bob <bob@hermitagewood.com> wrote: Steve,
Yes, at least one source of that is the Chittenden book (Performance
Tuning the Sunbeam Tiger), which is what prompted my decision to bore the
block .200 against the recommendations of the machine shop. There must be
at least some truth to it, since I did have cylinder walls left when the job
was done. Based on this, I suspect a Tiger block can accept a substantial
over bore, probably more than piston manufacturers offer. Looking at my
old block, I would think a .120 over bore would be fine, but that is just me
thinking aloud.
In the end, stories of flexing cylinder walls, poor ring sealing, and
the propensity for over bored engines to run hotter (a problem no Tiger
needs) convinced me it was just easier to get another block. I'm curious
to know what Bugz has in mind, because I can't see justification for boring
the 260 block any larger than is required for cleanup at rebuild time.
Maybe he's looking at a piston/rod swap that makes for a better rod to
stroke ratio by changing the piston pin location?
--Bob
>Bob,
>
>As I recall, the industrial Tiger "260" was not the same block as the
>production passenger car "260" (see freeze plug count). And the casting
>method of the "289" differed in that some cylinders were "siamesed" to
>allow wall thickness for the bigger bore.
>
>___
>Steve Laifman
>Editor - TigersUnited.com
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