[unruhjonny]

I came across something on facbook this evening, and it lead me to do some personal research - I couldn't find anything, so I figured this might be as good a place as any to post it.

The item in question is a 1967 Pontiac 400 casted on November 5th 1966 (assuming my memory serves me for casting dates correctly).
The blocks owner is saying it's a service replacement Ram Air block;
But I think he's mistaken... possibly because a purported RA block can get him extra money...

If my memory serves me the SR-number was stamped by the dealership when it was about to be installed in a car as a warranty replacement block (or something like that), and that (with the SR being self explanitory) the numeric code was directly tied to the warranty work;
So no two engines would have the same SR number.

Is this correct?

I ask, because the blocks owner is asserting that this specific SR number was used for RA blocks...
except the block appears to have standard 400 slugs, and two bolt mains(!?)

It seems that there is some confusion with the RAI-RAII-RAIII-RAIV progression, where the RAIII was little more than a renamed (1967-1968) HO engine that acted as a stop gap between the standard 400/4bbl and the "real" Ram Air engine (the RAIV);
I say that because the 67-RAI, 68-RAI & RAII, & 69/70 RAIV always had four bolt mains, while the majority of 69-RAIII used two bolt mains, then for 1970 Pontiac did an about face and made the majority of the RAIII as four bolt blocks...
Sorry if I seem to be rambling, I hoping to end up here with a clearer understanding of what necessitiates a true original or service replacement RA block.

I did several searches, and found some posts of what surely looked to be SR RA blocks, they always had four bolt mains, and sometimes had a year casting by the distributor which greatly preceeded the casting date;
The blocks always had different SR-numbered blocks too.

Can someone confirm, or correct me on my understanding of the SR-numbered blocks?

Can anyone offer why some SR blocks were casted sometimes years later than the blocks cast model year date - I had understood that the 67-72 (or so) blocks were all just as good as one another - with only the finishing work being what seperated one engine from another...

I didn't come actoss anything in my Pete McArthy book on this subject either... but maybe I missed it(?)

Also, to further hnderstand this, If I was a tech who was going to do a warranty replacement block for a customer with a 1968 RAI car, would I have recieved a four bolt short block, and swapped the customers top end and exhaust parts over - or was a it a complete engine...

I thank anyone in advance for chiming in and sharing your knowledge.

[sleddog]

Good Questions... Looking forward to the answers.

[AG]

Each SR block has a unique number as far as I know.

[Rocky Rotella]

The SR number was stamped at the Pontiac Assembly plant. It corresponded to the red tag that was wire tied to the block. What I believe was the SR number was akin to a production block's Engine Serial Number. And the SR blocks were produced as an SR order arrived. So while no two SR blocks will have the same SR number, the SR number is only useful to Pontiac's internal paperwork at that time.

The SR blocks were the fitted block only (machined block, caps, pistons and wrist pins, etc). If whatever else was needed during a warranty claim or major failure repair was ordered separately.

The block itself was constructed of whatever production block was available at that time. So, for instance, a 67-70 RA block that was SR requested during the early 70s was constructed of a typical 481988 block that was machined for and fitted with 4-bolt main caps. The "481988" cast into the block was ground away and "9799915" was stamped into place.

There were single SR blocks that fit a wide array of applications. So most early 70s 455 SR blocks will have 4-bolt caps regardless of the application so it could fit the 4-bolt 455 HO or 2-barrel 455 with 2-bolt caps. Etc.

[unruhjonny]

thanks for speaking up Rocky!

What I believe was the SR number was akin to a production block's Engine Serial Number. And the SR blocks were produced as an SR order arrived. So while no two SR blocks will have the same SR number, the SR number is only useful to Pontiac's internal paperwork at that time.

Did you mean "Engine Unit Number"?
(if so, that makes a good amount of sense)

I sincerely appreciate you expanding upon what I had previously understood.

regarding this part of your post:

The block itself was constructed of whatever production block was available at that time

That makes sense to a point;
The following two blocks seem to confuse things a little bit though - so could you offer an explanation as to why a "1967" or "1968" block was cast during the 1970 model year?

1967 block cast March 6th 1970


1968 block cast May 10th 1970

[grandam1979]

That looks like my block did I send you the picture of the 68 block? If so it was produced in 1970 and only has 2 engine mount holes on each side.

[unruhjonny]

I hotlinked those both from their respective threads here.

Yours was one of the threads I found last night when I was looking to fill in the blanks BEFORE I made my post;
HERE is your original thread.

In the case of the FB block, it was a 1968 block produced as a SR engine during the 1967 calender year - so there's little to be confused about (meaning it was a 1968 block cast during the 1968 model year, as a service replacement engine), and now that I have received some feedback I am confident this guy is just upselling (intentionally or otherwise) his block
I did find a very similar (albeit legitimate RA block) here - cast a month after the FB block;
LINK

[Rocky Rotella]

Well, the Engine Unit Number (EUN) or Motor Unit Number (MUN) are general (and accepted) terms that refer to the Engine Serial Number (ESN), which is what Pontiac technically called the engine's sequential build number.

In the example of your 1967 block cast during 1970 model year, there were certain instances, and I don't know the reason, that Pontiac went back and revived a former casting. It may have been by special request by someone within the foundry or division or to fill specific criteria that the current production casting didn't possess. I don't think we'll ever know the reason.

I've also noticed that the SR8 number (which signifies Service Replacement 8-cylinder) is progressive. Blocks in the early-60s were in the 3000s. By the mid-70s, they were approaching or had surpassed the 9000s. It's my understanding that the SR8 number was similar to the ESN on the block and that no two were alike. If that's true, was it possible that Pontiac had only produced some 10,000 (or so) SR blocks in the 26 years its V8 was in production? It sure seems that way.

[unruhjonny]

huh!

Thanks for expanding upon your lat post Rocky!

[JLMounce]

Originally Posted by Rocky Rotella

Well, the Engine Unit Number (EUN) or Motor Unit Number (MUN) are general (and accepted) terms that refer to the Engine Serial Number (ESN), which is what Pontiac technically called the engine's sequential build number.

In the example of your 1967 block cast during 1970 model year, there were certain instances, and I don't know the reason, that Pontiac went back and revived a former casting. It may have been by special request by someone within the foundry or division or to fill specific criteria that the current production casting didn't possess. I don't think we'll ever know the reason.

I've also noticed that the SR8 number (which signifies Service Replacement 8-cylinder) is progressive. Blocks in the early-60s were in the 3000s. By the mid-70s, they were approaching or had surpassed the 9000s. It's my understanding that the SR8 number was similar to the ESN on the block and that no two were alike. If that's true, was it possible that Pontiac had only produced some 10,000 (or so) SR blocks in the 26 years its V8 was in production? It sure seems that way.

If true (and it certainly seems plausible) that's a pretty incredible figure! Obviously that would only cover issues that occurred that required a new replacement block, but still, even taking that into account, it could be seen as a testament to the engine's reliability.

[tekuhn]

I just happened across this discussion, but I have some pictures of a 1970 RAIV SR block (NOS in Cosmoline) that will confirm what is being said. The SR# stamped onto the block corresponds to the red SR tag that is wire-tied to it. This block was manufactured from a 1973 block that was restamped by grinding off as many numbers as necessary to restamp with the correct 1970 number. In this case it required the entire 1973 number to be ground off. This particular block was shipped with fitted pistons - cast pistons indicating it was intended to replace a RAIII even though it has the RAIV part number.

[unruhjonny]

thank you very much for sharing this!!

I am curious as to how this engine survived so long, not having been installed in the warranty claim vehicle!?

[tekuhn]

I can't answer that. I bought it about five years ago on eBay from the brother of the original owner who had passed away before using it. It had apparently been sitting in his attic for years.

[Rocky Rotella]

Thanks for sharing, tekuhn!

Jonathan, SR blocks weren't limited to warranty claims only. I'm certain that you'd receive the same SR block assembly if you went into your local Pontiac dealer and ordered a block for the specific application. I know racers did it regularly. I also believe that Pontiac may have made small runs of certain popular applications to keep on hand. For instance, I have recorded several 9799915A SR blocks (tekuhn's is now included) that were cast A063.

[grandam1979]

The thing I don’t understand is the SR block I have was cast in 1970 but only has two mount pads on each side so it’s not a block used in production in 70

[unruhjonny]

Originally Posted by grandam1979

The thing I don’t understand is the SR block I have was cast in 1970 but only has two mount pads on each side so it’s not a block used in production in 70

I believe Rocky already addressed this:

Originally Posted by Rocky Rotella

...
In the example of your 1967 block cast during 1970 model year, there were certain instances, and I don't know the reason, that Pontiac went back and revived a former casting. ...

So the older casting was revived for that one.

[242177P]

Originally Posted by unruhjonny

I say that because the 67-RAI, 68-RAI & RAII, & 69/70 RAIV always had four bolt mains, while the majority of 69-RAIII used two bolt mains, then for 1970 Pontiac did an about face and made the majority of the RAIII as four bolt blocks...

Minor quibble to be sure, but most 67 Ram Airs were two bolt. The four bolt did show up in 67, just later in the model year.

[unruhjonny]

Oh - ok;
I don't seem to recall that from Rocky's 67-69 Firebird book, but I'll take that at face value.

[242177P]

Originally Posted by unruhjonny

Oh - ok;
I don't seem to recall that from Rocky's 67-69 Firebird book, but I'll take that at face value.

751 GTOs as compared to (IIRC) 65 Firebirds, and the Firebird was 'late'. So perhaps they were (in Firebirds) all four bolt?

[unruhjonny]

sounds reasonable to me.

Before you mentioning it, I dodn't think I have heard that the 1967 RAI could have been built with two bolt mains...