Steve,
Not quite, more like .010" to .020" offset. An yes, the rods, crank and wrist
pins hold
up fine with 500 HP coming out of a 247. The change is taken up by the large
clearance
between the rod small end sides and the piston. JBA uses this method on all of
the 427's
they rebuild.
As a matter of interest, Ford used special boring bars when machining the holes
in the
first place. The boring fixture would reach in through the core support holes
(we call
the freeze plug holes) and grab the outside wall of each jug. The bore would be
then
centered on the outside wall. I believe the stock wall thickness of the
cylinder was
about .130", so you can see there is not much room for error. JBA claims that
the minimum
acceptable wall thickness is .095" and that may cause hot spots. My 427 was
bored .030"
and has a measured wall of .093" (the discrepancy is years of corrosion in the
water
jacket) . It runs cool, puts out 450 HP and does occasional track duty with no
problem.
(Knock on wood) Maybe I'm lucky.
Craig
Steve Laifman wrote:
> Craig Wright wrote:
>
> > They
> > boring bare is shifted to place the bore in the center of the remaining
>walls
> > resulting in fairly uniform wall thickness. Sonic testing will tell you if
>you can
> > rebore your 260 and how much.
> >
> > Craig Wright
>
> Craig,
>
> While the core may shift, causing uneven wall thickness and affecting re-bore
> capability, the centers of the bores are done with great precicion to put the
>pistons
> and rods over the crank journals. Are you suggesting a 0.020 to 0.030 bore
>offset,
> to compensate for a bad jacket thickness, will not adversely affect the
>rod/crank
> alignment and loads?
> --
> Steve Laifman < One first kiss, >
> B9472289 < one first love, and >
> < one first win, is all >
> < you get in this life. >
>
> _/_/_/_/_/_/_/
> _/ _/_/_/ _/_/_/ _/
> _/ _/ _/ _/ _/ _/ _/_/_/_/
> _/ _/ _/ _/ _/ _/ _/
> _/_/_/_/_/__/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
> _/
> _/_/_/
--
**********************************************************************
Craig Wright Product Design Group, Inc.
craig@p-d-g.com 4635 Viewridge Ave.
(619) 569-3484 x309 San Diego, CA 92123
fax: (619) 569-3490 http://www.p-d-g.com
**********************************************************************
|