TAC Tech > Number Crunching

Stamped codes on Service Replacement Block

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MalteseFalcon:
I picked this up and got it home this week. Service Replacement block dated October 5, 1973; the 4-bolt mains are are from another engine and I will need to get it line bored. But I had a couple of questions. It looks like it has the code "88 89 6" stamped in about the place where you would normally see the engine code for the application - like "WC" on a 1978 4-speed 400. Does anyone know what it means?

Also, I noticed that the three 4-bolt caps have the numbers 2, 3 and 4 cast into them - that makes sense. But in addition, on the other side of the cap, they have 7100, 7101, and 7102 cast into the caps with 2, 3, and 4, respectively. What is that for?

I think the front main bearing cap has a casting date on it, but I can't make it out. I guess they could be from any 4-bolt from a 421, 428, or 455.

Also, here are pictures of a nice clean 455 4-bolt block for your viewing pleasure.

Thanks!

firebirdparts:
I always thought the number next to the engine code was for record keeping purposes in the engine assembly area.  They don't link directly to the build sheet though.  At least I don't think they do.

Rocky Rotella:
The 7100 to 7102 are the last four digits of the individual part numbers of the main caps. What many do not realize is that all five caps were cast as a single unit, rough machined, cut apart, installed on the block and finished machined. They were then specific to that block and will not directly interchange with another block without machining.

Curiously, what makes you think they are from a different block?

While I can't decipher the "88 89 6", the SR8 number lower is Pontiac's internal identifier.

Can you provide some additional images of the casting number and cast date? I'd love to add these images and information into my SR data base.

MalteseFalcon:

--- Quote from: Rocky Rotella on October 19, 2021, 08:42:25 PM ---The 7100 to 7102 are the last four digits of the individual part numbers of the main caps. What many do not realize is that all five caps were cast as a single unit, rough machined, cut apart, installed on the block and finished machined. They were then specific to that block and will not directly interchange with another block without machining.

Curiously, what makes you think they are from a different block?

While I can't decipher the "88 89 6", the SR8 number lower is Pontiac's internal identifier.

Can you provide some additional images of the casting number and cast date? I'd love to add these images and information into my SR data base.

--- End quote ---

Hi Rocky! Thanks very much for your response. I didn't known that all 5 mains were machined from one original casting; I assume that was to ensure consistent properties in the all of the caps on one engine?

Here are pictures of the casting number (485428) and cast date - J053, or October 5, 1973, for the SR block. I had to reduce the size to upload them here; please PM if you would like higher resolution copies of them or any of the others.

Regarding the caps, I was told by the seller that they were from a different block, and I believe that he had put them on this one. I tried to get a better picture of the date code on the front cap, and it's hard to photograph. The first letter could be an "L" or a "C" (or just about anything else); I think the next is 15 or 13; and I'm pretty sure the last digit is a "2". 

I recently got another 455 block and heads which some people have told me is kind of interesting. It's a 483677 casting with a cast date of "H180", which in this case I believe is August 18, 1970. It has 2 bolt mains. There is a "71 "cast into the block, it has "C028808" and "YC" stamped on the front of the block and has #66 heads. I was told it was removed from a 1971 Grand Prix . Using the Wallace Racing database, this decodes  to a 1971 455, 325 HP, 8.2 compression, 067 cam, automatic. Pictures in the next post below. Perhaps the only interesting thing is that the 483677 block appears to be a short production block, used in 1971 between the 9799140 and the 485428 on all 455s, including the '71 455 HO. I think I read that the 483677 block might be a little thicker in the webbing than the 485428.  I think that might be in your Definitive Firebird and Trans Am Guide, 70 1/2 to 1981 .

Speaking of that book, are there plans to do a second printing? I'm still looking for a hard copy, and judging by the prices in the resale market for it, your outstanding book is, not surprisingly, in very high demand. My Firebird library goes back to first editions of Michael Lamb's The Fabulous Firebird and Joe Oldham's Supertuning Your Firebird Trans-Am (I'm not a book collector, that's just when I bought them), and a lot since then, and your careful, thorough, investigative approach to research takes things to the next level.

MalteseFalcon:
Pictures of 1971 483677 block.  As noted above, it's a 483677 casting with a cast date of "H180", which in this case I believe is August 18, 1970. It has 2 bolt mains. There is a "71 "cast into the block, it has "C028808" and "YC" stamped on the front of the block and has #66 heads. I was told it was removed from a 1971 Grand Prix . Using the Wallace Racing database, this decodes  to a 1971 455, 325 HP, 8.2 compression, 067 cam, automatic.

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