[2manyT/A'S]

Originally Posted by zeebo

so this begs the question..are there any differences in 455 blocks from 70 to 76? discounting the ram air blocks and four bolt mains in some....

Same deal on the 75/76 455 blocks....

NEW 500813 casting ID.

Best to stay with 485428 for ANY serious HP builds.

[GTOLou]

Originally Posted by 2manyT/A'S

Same deal on the 75/76 455 blocks....

NEW 500813 casting ID.

Best to stay with 485428 for ANY serious HP builds.

TooMany - I didn't think the undercut cap rails were present on the 455 blocks for those years...you got any pics? It is pretty dramatic w/ the 400 blocks as far as the missing meat in that area.

[2manyT/A'S]

Originally Posted by GTOLou

TooMany - I didn't think the undercut cap rails were present on the 455 blocks for those years...you got any pics? It is pretty dramatic w/ the 400 blocks as far as the missing meat in that area.

No.....just assuming that they cheaped out on the casting & it would have greater potential for similar type problems to develop......

The casting # wasn't changed for NO reason.

Anybody done a weight comparison?

[GTOLou]

Originally Posted by 2manyT/A'S

No.....just assuming that they cheaped out on the casting & it would have greater potential for similar type problems to develop......

The casting # wasn't changed for NO reason.

Anybody done a weight comparison?

I'll post a pic of a 76WX block - way more meat than was around the mains of the 557. Heck, the 557 is so poorly cast under the main caps that you can't add standard four bolt main caps - they'd drill through. I'll post a pic.

[72blackbird]

Maybe us 500557 owners can copy a page from the hi-po 403 Olds owners and run a halo girdle and a main cap brace that ties into the oil pan rail. It would be cool if we could run 4.21" and 4.25" stoker kits w/ no fear of block breakage as well.

Geno

http://www.jsmachineoldsmobile.com/images/full.JPG

[mgarblik]

I feel that the 375 HP limit mentioned in a couple posts is reasonable for a "557" block. Remember that's a 100% safety margin for the original design parameters give or take a few HP. These were designed for 185 HP and 4500 RPM's. So likely good for the 375 HP level and 5000 RPM's for an occasional blast on the street. Unless doing a numbers matching restoration, I would bypass that inferior casting for the much better ones still out there. JMO.