crank question...

[turbo89]

They didn’t change it to improve strength. The baseline stuff was good to at least 400hp and none of the production stuff to that point even made half that except the 84-85 which was a whopping 200hp. The 85 block is 20 bolt pan with the same lifter area as the earlier blocks. Why? My guess is they are constantly Re-tooling and probably didn’t have the later recessed head bolt tooling the later blocks used ready to go they just went with what they had for production. The deck height reduced and head gasket change. Could have even been ergonomic reasons for the change. Could have been to reduce time from foundry to assembly line. The later blocks have more machined featured that required less manual input. The recessed head bolt is beneficial as it reduces deck distortion. The oil pan doesn’t increase block strength. Why didn’t they go to 25 bolts if more is better. They had the space.


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Brian i think his point is the pan area is beefier on the 109's .. also alot more metal added to KEY areas all which help overall block integrity

The rails are thicker .. on the 20 bolt blocks

The 84-85 329 blocks were 14 bolt

 

[bison]

Brian i think his point is the pan area is beefier on the 109's .. also alot more metal added to KEY areas all which help overall block integrity

The rails are thicker .. on the 20 bolt blocks

The 84-85 329 blocks were 14 bolt

The areas of concern on an old production Buick block are the mains and webbing. That’s what’s holding the crank in as it’s being driven towards the pavement. The BMS blocks are 14 bolt pan rails. The main webbing is very thick. Probably 5 times as much material in those critical area as well as additional fasteners to keep the mains from moving. I’ve never seen a cracked main webbing in one though it’s probably happened.


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[pacecarta]

if i had to guess ..the 14 bolt to 20 came from the need to stop leaks ,
the 109 valley change was just easier when someone realized they could use the the same bore for the lifters to provide oil drain back in the valley and a flat surface there would be easier to work