1968 SR block question D100
 

It’s a SR block date code D100 but the block only has two mount holes on each side. All the other SR blocks cast in 70 or 71 I have seen have all five mount holes.

maybe a strike era block

What is the block number? Looks like a 68 block. Perhaps the date code is incorrect?

It's a 68 SR 4 bolt I had a 69 ram air IV SR block cast in 71 that had all 5 mount holes.

What does the 85650 stand for on a SR block

Interesting. What is the casting number? Is the number as cast or ground and re stamped?

Not sure anyone knows for sure. SR likely stands for "Service Replacement"....the leading digit "8" might decode 8 cylinder engine....the last 4 digits are a mystery it seems...

The digits after SR are a sequence. For instance, this block is SR85650. The next SR Block would be SR85651... Is the block for sale?

No it’s not for sale it’s my next build. The block is ground 2506 but looks double stamped.

Here's an SR block that is in a 68 GTO Convertible. Later casting date number of September 23, 1971, smaller SR number, has the 5 engine mount holes, and drilled for 4-bolt mains with 2-bolt caps.

Did the SR numbers start over every year?

Double stamp

The 9792506 that is in the picture is a 1968 Ram air I or Ram air II service replacement block that was manufactured on April 10 1970

Actually, with a 1970 cast date, it's probably a 1969 Ram Air IV Service Replacement
 

Although the casting/stamping number is the same for 1968 RAI, 1968 RAII and 1969 RAIV.

And, being cast in 1970, it was most likely originally a 9799914 400 2-bolt main block.

The double-stamping (with 2 different font sizes) is peculiar. I've handled about a dozen ground-and-stamped SR blocks, of various vintages from 1967 to 1973 and all had the LARGE font stampings.

I've never seen one re-stamped with the little font size. Who knows.

That pad looks machined, not cleared with a hot knife or ground.

What are the casting numbers on the caps?

With only 2 motor mount holes per side and the large "68" by the distributor hole... wouldn't this indicate the block started as a 9790071 casting?



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You're right, it's probably a 9790071 casting
 

I'd guess that there is not the 'O/O' casting in the lifter valley, which a 9799914 block would have.

Boss, I thought the same thing about the ground area - it somehow looks wrong. But I was kind of concentrating on the font size of the stamped digits.

Maybe it was a new guy working on the casting/foundry line?

Also just noticed the chrome plated hex steel block drain plug in the 2nd photo at the beginning of this thread. Now would be a good time to ditch those and go to a brass plug. Last set of the chrome plugs I came across we ended up having to carefully drill them out and extract them piece by piece. They rust very securely to the block threads after a year or two.

It has no OO in lifter valley.

Just got another 400 SR block SR811992 D201 that’s 6342 higher than the other one cast 1 year earlier D100 not sure it means anything but just over 6000 service blocks would seem about right in a year. I’m wondering if the engine size was a factor in the numbers on block?

Maybe Rocky will see this thread?
He has some interest in these blocks.



:)

Could that 85650 number have anything to do in relation to the 87684 GTOs that where made in that model year?

Grandam1979, can you attach some pictures of the new SR block? And are the numbers cast or stamped? I'd love to add them to my collection.

Concerning the numbers, as Johnta1 pointed out, I've been tracking SR blocks for years. While they're certainly not rare, there aren't as many out there as people might expect.

What I can tell you is that I can no correlation to the sequence following "SR8" (which signified Service Replacement 8-cylinder). Most are higher than those produced during the preceding calendar year, but some are lower. Some produced in the same model year may be 10,000 units off. I don't know that Pontiac kept any specific record of them.

I supposed the bigger question is, how many warranty failures did Pontiac have that required a new fitted block (block, main caps, and pistons) each year? If I had to guess, I'd say it's a relatively low number. And combine that with the sheer number of fitted blocks Pontiac sold over the parts counter to racers, the SR blocks that are out there, not all were destined for warranty repair.

If anyone has any other insight on the sequencing (or paperwork that clarifies it), I'd be interested in learning more!

Pictures,

On the service replacement (9792506 ) 400 ra blocks the factory ground off one of the engine mount bosses so that would not be able to be used in a 70 up application very strange but I’ve seen many like this

This block has one removed

All I know is I replaced two of them in early 1970 that were 1969 RA-IV 400 engines.
In both cases the block was changed as well as related required parts. Both engines in my opinion were abused prior to the failures.

Tom V.

Thank you!

Would you mind posting a picture of that too?

Rocky,as I remember(kind of).When we ordered a over the counter block in the early 60s it was a bare block.Are not SR blocks a fitted block with pistons?Tom

Tom,

As I understand it (and Nunzi recalled it this way, too), Pontiac didn't sell bare blocks via the parts counter. The SR assemblies were always fitted blocks, which included main caps, cam bearings, and pistons with wrist pins and rings. Was it possible that Pontiac offered something different in the early years? That may be, but I can't recall ever seeing a part number for such in the parts catalog for any year. Obviously, back-doored stuff notwithstanding.

Pictures

Whitmore told me the 1970 10-1 455 with 64 heads ( I have one) had a fair amount of comebacks due to people not running premium fuel. It had cast pistons and they cracked and took out a few engines. He was a dealer mechanic back in the day.

Thanks for the pics! Can you confirm these are of the 9790071 or 9792506 block?

Thanks, I could certainly see that happening.

The question is, did Pontiac ship 10,000 (or more) SR blocks each year? Or were SR numbers picked at random. I just don't know at this point. But I'll keep looking!

071 block

MIKES Question IS: 9790071 casting, # "979" IS keeping with in THE SERIES OF ALL THE BLOCKS- CAST, "00" IS 400, "NOT" WRITTEN ON THE INSIDE NOR the OUTSIDE of THE BLOCKS AND 71 IS 1971. This SEEMS A LOGICAL WAY that THE factory could DEPICT THE SERVICE BLOCK in order to differentiate them from the originals?



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Absolutely nothing to do with it.
 

9790 is the first four digits of all CASTING numbers assigned to CAST IRON parts in 1968.

The 071 is just the rest of the original 400 CID block part number.

That's it. Nothing special.

Can anyone who has a old GM parts book please list the part numbers for the service replacement fitted blocks in terms of the 68 RAII and then the 69 and 70 RA4 , because these 3 fitted blocks should have the TRW forged pistons unlike the 400 motors that what we now call the RAIII motors.

Thanks in advance!

Mike would like to know: Did the 455 ci or SD use a 60-80 psi pump spring that was problematic 1n the early 1970's that a mechanic helped the factory in testing and development due to a spring pressure issue, causing those Engines to fail early? " Not" the fuel being the actual cause of failure on those 455 ci Blocks.

only engines that used the 80lb pump was 455SD and RA Vs.They also used a larger dist gear requiring a larger dist hole.VERY EZ to tell a SD or V block from a distance.Tom.Tom

Mikes Question is: In creating a 389-400 ci Replacement Block "Did the Pontiac Factory use one of the original 1968 Plugs to form a Cast in the manufacturing of this 1970 Replacement Block in this Post, so that the completed Cast is both new and as original as it could be?" I ask this because I see 68 Cast into the top of the Block near the Dist. hole and the cast date depicts 1970.

Here's another question .
Has anyone ever seen a factory replacement block for a 389 that had the 3 freeze plugs per side?

67 was a bit of a crazy year for the factory with the change over/ overlap of motors!

There was a 66 389 SR block on ebay last year that had the 3 freeze plugs. It was unused and had the pistons with it. Was cast is mid 68 I believe.

Here is a thread I started on one I found.

https://forums.maxperformanceinc.com...d.php?t=836287

I have a 421 SR block that has 3 freeze plugs. Basically just a 1967 4 bolt 428 with a 4.090 bore.
Casting number was ground off but never restamped.

@Rocky, I don't mind sharing the details on the SR block that I own. It is an NOS #9799915A which is the 1970 Ram Air IV part number. It was cast on January 6, 1973. It was fitted with cam bearings, cam retainer, galley plugs, freeze plugs, head dowels, timing cover dowels, 4-bolt main caps, and pistons with pins and rings. There are all 5 mouting pads machined, drilled, and tapped. There is no large year cast near the distributor hole. The factory wire-tag with matching SR number was still attached, and the whole assembly had been dipped in Cosmoline to preserve it. The entire part number was wiped or ground off and then restamped since the '73 part number would have been completely different.

Interestingly, the pistons appear to me to be cast. I assume perhaps they used these for replacement of both RA-III and RA-IV engines and equipped them with either cast or forged pistons accordingly. That would make sense since most if not all '70 RA-III engines had 4-bolt main caps (unlike '69).

The block is still un-used, so please let me know if you need any more pictures or information.

A few more pictures:

This piston thing needs more investigation!

Are we to assume that all RA4 fitted replacement blocks destin for warranty for the 1970 model year got built with cast Pistons , or after that intial run of warranty fitted short blocks built with the forged Pistons ran out, that from then on ( like by 1973) all factory fitted RA4 blocks where just intended for over the counter sales ( since warranties would be over) and thus built with the standard cast Pistons?

tekuhn, thank you so much! That's very helpful!

Steve, Pontiac had three separate service replacement applications for the 1970 model year.

479877- all 400 except Ram Air (presumably with 2-bolt caps)
479878- Ram Air III (four-bolt caps with cast pistons)
479879- Ram Air IV (four-bolt caps and forged pistons)

We can surmise that tekuhn's above is a 479878 assembly as it has 4-bolt caps and cast pistons. Since the 9799915 casting would have been used with cast and forged pistons, I've often wondered if the "A" denotes lesser/wider wall clearance for piston use? And since tekuhn's is cast A063 (which is shared by many 9799915 SR blocks I've documented), it certainly started life as a typical 481988 block that was fitted with 40bolt caps during machining and stamped accordingly for the 1970 application.

It does beg the question, if they were going to distinguish 4-bolt blocks for cast pistons by adding the "A", why not just stamp it as 9799914 which was the Ram Air III casting number?

That's a good question. I should have explained. I have yet to come across an SR 9799914 block. That doesn't suggest that Pontiac didn't produce one, however.

I have data on (10) 9799915 SR blocks in my files. Of those (6) were cast A063 and it's only those that are stamped "A" or "B". The other cast dates were partial cast/stamped 9799915 or fully stamped 9799915.

For those cast A063 that are/were NOS, those stamped with an "A" were tagged 479878 and included cast pistons. Those stamped with a "B" were tagged with 479879 and had forged pistons.

Has anyone came across a 9799914 SR block? And if so, what was its cast date?

A quick search revealed this 9799914 block, which was equipped with 2-bolt caps.

http://forums.maxperformanceinc.com/...03#post6000803

Apparently Pontiac used "9799914" in SR applications for 2-bolt applications (479877).

Lots of interesting information, thank you.