[DeTomaso] 2-bolt versus 4-bolt

[hoppe1 at cox.net]

I don't think I have heard this said before, but I was around when street talk about Chevy vrs Ford 350 vrs 351 and always thought that the reason ford added the extra 2 bolts was because the Chevy 2 bolt was not strong enough and Chevy went to a 4 bolt block.  Well ford could not let that be said about ford only being a 2 bolt so they added them.
Rich Hoppe

---- Mad Dog Antenucci <teampantera at yahoo.com> wrote: 
> 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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