[DeTomaso] 2-bolt versus 4-bolt

[Mad Dog Antenucci]

And how did your discussion (s) go regarding Cleveland issues like for lack of the proper term; 'thin-cast-block', core shift,  etc. with regard to rece preped blocks?
   
  md

"John Bentley (jab)" <jab at cisco.com> wrote:
  yes, he was.

JB



________________________________

From: Mad Dog Antenucci [mailto:teampantera at yahoo.com] 
Sent: Friday, October 26, 2007 3:16 PM
To: John Bentley (jab); detomaso at realbig.com
Subject: Re: [DeTomaso] 2-bolt versus 4-bolt


JB,

Good stuff....Thanks for sharing....Wasn't your dad involved with
Cleveland development?

Dawg

"John Bentley (jab)" wrote:

For those interested in engine engineering, I recently had an
email
exchange with my Dad (engine designer at Ford) on pros and cons
of the 2
and 4-bolt blocks. Here is what he had to say.....

************************
2bolt/4bolt
The V engines produce high main bearing loads due to gas loads
at
approx. 45 deg. from the horizontal, and as the RPM increases
the high
loads are produced at all angles. Sideways loads to the right
cause the
left outboard side of the cap to lift away from the block. When
the
bolts are near the bearing bore as in the 390/428, the contact
pressure
between the block and cap is quite uneven, which makes lift-off
easier.
The higher the side load, the more the lift-off. When the
lift-off gets
near the c'bore for the bolt, fretting occurs on the saddle face
and a
fatigue crack starts (crack is in fore-aft direction). The crack
progresses up the hole and thread until complete failure occurs.
The
extra 2 bolts were introduced to prevent the parallel-o-gramming
lift-off.

However, if the main bearing bolts are located farther outboard
towards
the center of the contact pad, the contact pressure is more even
and the
lift-off is minimized or prevented.

The 351C and 460 bolts are rather well placed, and that type of
bulkhead
failure never occurred (that I know of, in production engines).

There is no functional disadvantage to having 4 bolts, but it
provides a
margin of safety not generally needed.

One disadvantage of an aluminum block is that it has no
endurance limit
and therefore stressed areas will fail someday.

********************************

I guess I read from that you don't have to search the earth for
a 4-bolt
block unless you are building a pretty high HP engine.

FWIW,

JB


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Mad Dawg Antenucci 
Team Pantera Racing 
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