[pont406]

I was wondering if anyone knows what the numbers after the "SR" stamped on the front of the block mean? a part number? or just a casting sequence number?, I know its not the casting date or block casting number as they are in the normal locations

[steve25]

Can you post those numbers and the block casting number and date?

Also is it a 3 inch or 3.250" main Bore?

[Rocky Rotella]

I’ve been recording SR block numbers for quite so time. What I can say is that they seem to jump around. They all start with “SR8” which is followed by four or five digits.

The “SR” stands for Service Replacement. The “8” signifies 8 cylinder (A “6” was used in this place on OHC-6 engines). And the numeric sequence was the engine serial number. At first I thought the serial numbers were sequential, but I don’t believe that to be true any longer. They’re generally 10,000 or less.

It’s interesting to note that SR blocks were sold as a “fitted assembly.” That means a machined block with main caps and pistons/wrist pins.

Can you share your numbers?

[pont406]

Originally Posted by Rocky Rotella

I’ve been recording SR block numbers for quite so time. What I can say is that they seem to jump around. They all start with “SR8” which is followed by four or five digits.

The “SR” stands for Service Replacement. The “8” signifies 8 cylinder (A “6” was used in this place on OHC-6 engines). And the numeric sequence was the engine serial number. At first I thought the serial numbers were sequential, but I don’t believe that to be true any longer. They’re generally 10,000 or less.

It’s interesting to note that SR blocks were sold as a “fitted assembly.” That means a machined block with main caps and pistons/wrist pins.

Can you share your numbers?

here' s the pics 62 389 block

[steve25]

Can you post up a picture of either side of the block back by the bell housing flange?

Does the block have a reinforcement wing cast in from the lower side of the rear deck to the bell flange?

[1funride]

Were the SR blocks made from stronger castings or the lightened 557 castings?

[Old Goat Racer]

Here are some pics of my 455 4 bolt main SR block.
SR8 1758

For Rocky

The guy I bought it from installed an NOS SD crank and TRW forged pistons. And topped it off with 455 SD heads.
I don't have the heads.

[pont406]

Originally Posted by steve25

Can you post up a picture of either side of the block back by the bell housing flange?

Does the block have a reinforcement wing cast in from the lower side of the rear deck to the bell flange?

yes it has them

[steve25]

Then that is a casting of the 325A trophy block that was used for both 389 and 421 motors.

[hurryinhoosier62]

Originally Posted by 1funride

Were the SR blocks made from stronger castings or the lightened 557 castings?

Most are far stronger than the 557 blocks. In this case, it is a VERY strong block.

[unruhjonny]

this thread might also be of some assistance:

https://forums.maxperformanceinc.com...d.php?t=826840

[Rocky Rotella]

Originally Posted by pont406

here' s the pics 62 389 block

Thank you!

[Rocky Rotella]

Originally Posted by Old Goat Racer

Here are some pics of my 455 4 bolt main SR block.
SR8 1758

For Rocky

The guy I bought it from installed an NOS SD crank and TRW forged pistons. And topped it off with 455 SD heads.
I don't have the heads.

Thank you!

Do you happen to know if it has 4 bolt main caps?

[Rocky Rotella]

And as a note to all following this thread, my comment earlier about SR block number sequencing is visible here.

Pont406's SR block (cast Jan 16 1962) is numbered "1967" while Old Goat Racer's 455 (cast Oct 11, 1972) is numbered "1758".

I'm trying to determine how Pontiac decided upon their numbering system.

['ol Pinion head]

have a 428 4bolt SR in the rack, will get you the number Rocky.

[Rocky Rotella]

Thanks, Roger.

If you're able to snap a pic of the casting number, cast date, and SR stamping, I'd love to add them to my info. Also, if possible, can you tell me if it's two-bolt or four-bolt main caps?

[Old Goat Racer]

Originally Posted by Rocky Rotella

Thank you!

Do you happen to know if it has 4 bolt main caps?

YES it does.

['ol Pinion head]

Rock, it's a 4 bolt, will take some pics.

Originally Posted by 1funride

Were the SR blocks made from stronger castings or the lightened 557 castings?

Most SR 400's were the thicker web earlier block castings. that stated, 500557 casting SR 400 fitted blocks were built. Picked up a 557 SR fitted block many years ago, ended up using it in a '77 Y81 project.

[Rocky Rotella]

Originally Posted by Old Goat Racer

YES it does.

Thank you. I'm finding that all SR 455s from the 72-74 era were equipped with 4-bolt main caps.

[pont406]

My block is also 4 bolt main