[DeTomaso] 2-bolt versus 4-bolt

[John Bentley (jab)]

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)" <jab at cisco.com> 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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