SD 4 Block Markings (Page 1/1)
Rugger MAR 18, 07:58 PM
I recently acquired a Pontiac SD4 block and 99% of everything else I need to assemble the engine.

Can anyone tell me the significance/meaning of the stamped "INDY 002" shown in the photo. I read that Indy #2 was donated to the Indianapolis Motor Speedway Museum, so I doubt this came from that vehicle!

How about the marking that resembles a clock. Is that identifying the time of day (0700) that the block was cast, or something else?

Any help with any of the markings would be appreciated!









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1984 Indy Fiero #458
1985 Fiero GT

[This message has been edited by Rugger (edited 03-18-2020).]

fierosound MAR 18, 10:14 PM
Yours says 2.5 SD on the side.
GM I4 PN 10027634 is the same number as mine.
It has E245 cast on this side near the top and "Super Duty" on both sides.



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3.4L Supercharged 87 GT and Super Duty 4 Indy #163

[This message has been edited by fierosound (edited 03-19-2020).]

Rugger MAR 18, 11:12 PM
Appears yours was built on May 24, 1985 if I read the date code correctly.
My date code seems to read M222 (too dark to go to the garage and look now...will try again tomorrow) which could be Dec 22, 1982 or Dec 22, 1992 (although usually the code was "L" for Dec. Pontiac did use "M" at least one year 1967, I think..)

But that stamped INDY 002 in the first photo is curious to me and seems to indicate earlier than 1992....

Hopefully someone can help decipher this mystery!

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1984 Indy Fiero #458
1985 Fiero GT

wftb MAR 19, 08:58 AM
I have never seen a Super Duty block that did not have the words Super Duty cast in to it like Fierosound's block. The block in question has 2.5 SD cast in to it but it has the correct part # cast in to it. This suggests to me that it is a very early block. I do not know how to read the date codes though. I do know that the first run of super duty engine blocks were cast by John Deere, maybe they put a casting mark on there somewhere?

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86 GT built 2.2 ecotec turbo
rear SLA suspension
QA1 coilovers on tube arms

edfiero MAR 19, 01:04 PM
All SD blocks say 2.5 regardless of displacement, as the displacement 2.5, 2.7 etc is largely controlled by the crankshaft throw.

The INDY stamping appears to be done by the engine builder. That is not from the factory. Probably only Fred could comment on if the engines from the actual pace cars were stamped like that or not.
FieroWannaBe AUG 15, 01:28 PM
Late post, but, my block in my SD4 car is cast with 2.5 SD on it as well, it is an early block from early 1985:


From what I can see based of others photos, and the SD4 build guide. The blocks originally came machined off of the factory Iron Duke line. they didn't ship come with 1/2 head and main bolts. The cam tunnel only had 3 bearings like factory, and they were journal bearings, Those blocks are marked 2.5 SD below the distributer. Later blocks (I cant find the date change) came from GM with 1/2" main and head bolts, and had 5 journal cam tunnels with roller bearings, those blocks are marked Super Duty under the distributer.

EDIT: explained markings better.

[This message has been edited by FieroWannaBe (edited 08-17-2020).]

edfiero AUG 17, 11:17 AM
Rugger - how is your engine build going?
Did you ever get a better answer about the significance of the INDY 002 marking?