Does anyone know much about the 3951511 400sbc 2bolt replacement casting? Mortec says 'some replacements have 2 bolt mains.' Why did they make replacements anyway? The stock one suck that bad? When were these replacements made and how few are there? Are the rarer 2 bolt ones with the 511 casting any more/less strong then the 509 2 bolt casting? Also the 511's don't have accessory holes in the block on the drivers side, but a boss where one looks like it could have been machined. Are they all missing accessory holes there?

 

I have a '72 ,511 4 bolt main in mine and it has the bolt holes just like all the rest. as far as I knew all the blocks had holes just some of the heads did not. I don't know about the replacment blocks being anything special I think it was just a replacment for a block that was bad or was said to be bad the two bolts are said to be stronger but, how many people really push a stock block that far to find out which really is stronger?
maybe some can jump in with some info but, I don't think its that rare.

 

Still wondering what a 'replacement' block is.
This one came without the lower accessory holes. Now what would be a logical reason for this?
Could it be it was made for an industrial truck that wouldn't have accessories requiring those holes? That a 100% guess by me. Any other ideas?

 

well, what did it come out of? where did you get it?

 

It's a core, if I knew what it came out of I wouldn't speculate.

 

Answer at https://www.thirdgen.org/techbb2/sho...hreadid=199297