[DeTomaso] 2-bolt versus 4-bolt

[John Bentley (jab)]

to the best of my knowledge, core shift was an early problem.  I don't
think there is any more core shift than other thin-walled engines for 71
and later blocks.  The Cleveland was targeted as a high hp to weight
ratio engine so weight was removed wherever possible.  Most of my
discussion with him are limited to production performance, so highly
modified engines are outside our discussions.
 
Raced-prepped can mean so many things, its hard to say.  If you are
filling with Hardblock and using billet main cap girdle mods, etc., it a
different animal.
 
JB

 

________________________________

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


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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Mad Dawg Antenucci 
Team Pantera Racing 
The 1st & still the only vintage race team in open road racing 
www.teampanteraracing.com