[patrick1234]

So I was cleaning off my "original numbers matching" TA block today. I got to the front portion and busted out the razor blade gasket scraper. When I got around the water port not only did the gasket come off but a thin layer of bondo came off with my XL stamping. Lying underneith was the original ZC stamping. Looks like someone attempted to stamp a X in front of the number above it also, but that was hidden by the bondo. So my vin matches the vin stamping, my question is does it look authentic as in sizing and being on a angle? Or is the verticle stamping the original vin? Thanks in advamce for your knowledge on the topic.

[johnta1]

The angled one matches your VIN?

That one actually looks like the stamp except it is angled.
The vertical one looks too big?

What are the rest of the numbers on the vertical one?

Also is the block casting code 485428?
Don't know why one would go to that much trouble?
Different if it was for a 455 HO or even an SD?
(or something like that)

But hopefully it isn't a 350 from 1976?
(which would have a different block cast code)

[4birds]

The angled vin 23N****** appears correct in every way to me. ZC does show in some charts as a 73 455 manual trans F-body code, but not all charts. XL is an auto trans code. Is your car a FACTORY 4 speed or automatic? What is the vin stamped in the side of the transmission? I agree with John on the vertical #. Too big. The 0345910 appears correct also.
(I am assuming you have a 73 Trans Am by your avatar picture.)

[patrick1234]

Can't make out the rest of the verticle numbers. Yes, it's a TA 2v87y3n...Block casting is 485428. Plain Jane 455. Date codes of heads and intake are within 1 week of block and appear correct to me for when the car was assmbled. Interestingly, the 4x 1h heads on it have press in studs. I have some of the PHS docs but can't seem to figure out how to tell if it came with an auto. I don't have the build sheet. I went under the car and the trans tunnel doesn't have a big shifter hole in it so I'm going to say auto. The original th400 is long gone and the current one is from a Buick. The crank in this block is drilled for the pilot bearing.

[johnta1]

ZC would be a California car i believe?

Does it come from there?

[patrick1234]

Originally Posted by johnta1

ZC would be a California car i believe?

Does it come from there?

Yes, sold from jules Meyers out of LA California

[John V.]

As a fellow owner of a Jan built '73 TA, I'm sorry to take a contrarian view of your block.

First, it absolutely cannot have been an original XL coded engine.

The XL code was a post-EPA mandated EGR change code.

All EUNs after 0532727 and any engines that were in inventory with earlier EUNs as of March 15, 1973 were required to have the modified EGR and various other identifiers including specific paint color to distinguish them from early '73 engines. This is well established.

The XL code was not in use for EUN 0345910. BTW, the first character was always a 0 starting early during the '69 Model Year when Pontiac made a switch from 6 to 7 digit EUNs when it appeared they might exceed 1,000,000 units, they never did but the 7 digit EUN continued on. It will appear as a "C" for '73 EUNs because the 1st character "0" was chipped and did not form a perfect "0".

So what of the ZC code.

This was an early '73 455 code. But it was only used for the A & B Model Series, not the F (Firebird).

There was a wide range of early and late 455 codes. Aside from the distinction between early and late, specific codes defined the application by specific distributor. Each application had specific distributors, both points type and the electronic Unitized distributor (my own early engine TA was optioned with the Unitized distributor).

I am of the belief that your block was restamped with the matching VIN and the bondo work was done to indicate what might have been the correct engine code and to conceal the incorrect and impossible for a TA original stamped code. Except they goofed by picking a late code for the TA rather than a correct early code.

Furthermore, I believe the stamping that has appeared ending in 25714 is a partial VIN (last 5 digits) of the original Pontiac (A or B body) build that the block was original to.

As The Boss noted, the font of this other stamping could very well have been from a Pontiac Plant build VIN stamp.

Given the date codes and the EUN, I'm guessing the partial VIN can be extended to P225714 (some study of Pontiac Plant '73 VIN ranges would help to confirm my educated guess). Good chance that if you pulled the PHS for that partial VIN it would be a 455 equipped A or B body and the likely donor for the block (and possibly more) of the engine in your TA.

If the complete engine was donated and the original ZC code distributor remains, that would provide a further clue that the engine originated in an A or B body and not a TA.

There were no California specific 455 engine codes for '73. There were a few High Altitude 455 engine codes, both early and late. Specific distributors distinguished them. ZC was NOT one of these codes.

Consider this just one enthusiast's opinion. Don't like bursting anybody's bubble, but that is what the evidence says to me.

If somebody believes I am mistaken about the usage of the ZC, I'd welcome learning of the source material.

[patrick1234]

It is what it is and clearly not an XL code. The original engine distributor is gone and the engine was fitted with a HEI type.

[John V.]

The VIN stamp on that '72 Engine from a Pontiac Plant build is interesting.

Yes there were differences in VIN fonts from Plant to Plant. Norwood used the small font, Pontiac the larger font. Wasn't a big car vs. 'bird thing, whatever models the Pontiac Plant built in '73 would all have used the same style partial VIN stamping. There were many other Plants that assembled Pontiacs in '73, not sure what other Plants used the larger font.

I realize you are seeing them with your own eyes and I can only judge from the pic but the font style for the 2, 5, and 4 common digits isn't so obviously different with the possible exception of the 5. And I have only made an educated guess that it could be a Pontiac Plant VIN stamp. Could have been other Final Plants stamping larger VIN fonts in '73 or perhaps the stamps were changed at Pontiac between '72 & '73. Would want to see other '73 VIN stamps from Pontiac to compare.

What stands out to me is the location of the stamping. Am I correct that the location on the '72 block is almost exactly where the "25714" shows on the '73?

The Norwood partial VIN stamp would be less suspicious (IMO) if it wasn't for the Bondo work you discovered.

Regardless, it seems your TA should have a ZC code engine and the cast date works well for your Time Built code and ship date.

The rest of it is just detective work. Some will believe those extraneous nos. were added by a machine shop, others will believe they were part of a partial VIN stamp that would indicate the engine was original to another Pontiac. The truth will be hard to prove one way or the other and the scenario I mentioned about the engine having been stamped for one build and then transplanted because of a defect means it could have even happened during production.

If you get a chance to put a magnifying glass to the "25714", let us know if you detect any other characters.

I remain interested in this thread as my own '73 TA also has a Time Built code of 01D making mine pretty closely related to yours. I believe mine may have been finaled at Norwood perhaps just 1 day ahead of yours and shows a Date Shipped of 1/30/73. So have been learning a lot while following this thread.

[Held for Ransom]

The EUN appears to be too early for the change over of engine codes. Build date of body should be late January. What is the date shipped on PHS?

[patrick1234]

Shipped dat is 2-1-73. Date codes on all the pieces are in the middle of Decmber. looks like this thing was assembled in January, 4th week?

[Held for Ransom]

Jan. 22nd (Monday) -28th (Sunday). Still had 3 days before Feb. 1st (Thursday).

[patrick1234]

Originally Posted by Held for Ransom

Jan. 22nd (Monday) -28th (Sunday). Still had 3 days before Feb. 1st (Thursday).

So what;s your appraisel of the situation? Could this be an original block to the car? What was involved with the EGR change over?

[The Boss]

The other numbers close to the VIN look like the remnants of a VIN from a Pontiac Plant built car - upper end looks like there was some grinding going on. Pontiac had the larger font on their VIN numbers.

455 from a big car built in Pontiac originally?

[johnta1]

What is the date code on the block?

[patrick1234]

Originally Posted by johnta1

What is the date code on the block?

See attached pic

[patrick1234]

Here is the sticker, I would be interestd in seeing any other charts with PK on it. It talks about Cali emissions on the bottom. I've also included a pic of a stamping from a october 1971 455 block, the "big" fonts are totally different from the "machine shop" fonts on my block. Maybe this is a P vs N thing I don't know. I'm gathering that the big cars had bigger vin fonts? I have a 1972 California Formula FB and when I can get to the motor I may snap a pic of that vin and see what that looks like.

I've laminated the chart tith the F and ZC on it already.. I'm impressed that you guys came up with that.

[John V.]

John W., the EUN search seems to suggest that the ZC was used in the F body. I see at least 3 others that presumably are VIN matched plus 1 without a VIN. Unfortunately, your database does not indicate where they were originally sold, so we can only guess that these were delivered to Calif dealers.

Also odd that of these, 1 says it was a Formula, others say Firebird. The 455 was only available with the Formula and TA, right? Why were they described as Firebirds?

But I'm willing to concede that ZC (and likely then ZA also) were used in the F body.

unruhjonny, little doubt that the Norwood partial VIN stamp font looks correct on this block.

And if you are correct, the cockeyed stamping might be common for '73 Norwood builds.

But that doesn't prove it isn't a restamp.

HFR, I am not ready to believe that the other no. was the work of a rebuilder, it looks gang stamped like a partial VIN and the placement is common for a partial VIN from my limited experience.

If it was mine, I'd be inclined to pull the PHS on P225714 and see if it was a Calif build with a 455.

Invoice dates might also be of interest for that VIN to see if there is any discrepancy that suggests it went to major repair.

As The Boss says, he and I remain in agreement.

If it could be proven to be the original engine in the TA, it is certainly unfortunate that somebody fiddled with the Bondo and the code. But I suspect something is amiss.

If the extra stamping was done by a rebuilder it would be useful if the OP could confirm the block & crank have been cut. Seems that idea was put forward by the replies. He never said that the engine has been previously rebuilt.

Since the block is out of the car, I would also take a closer look at the area with a good magnifying glass. It is possible that more of what I believe is a 2nd partial VIN will be visible upon closer inspection.

[johnta1]

Why were they described as Firebirds?

They were submitted that way.
Didn't want to call it a TA if it might be a Formula or vice-versa.



I also would think the vertical numbers were the original VIN stamp, but I always figured the smaller stamps would be difficult to obtain to make the smaller stampings and make them look correct.

I also would have thought whoever did the 'bondo' job would have bondo'd the big numbers to hide them?

Probably never know what it is for sure, unless the partial VIN suggested by John, does show something from PHS.

[John V.]

HFR thanks.

In all these posts, never thought to compare VINs. Mine is 101 units earlier.

Might have been completed on the same day, perhaps they just shipped mine sooner? Was shipped to Mecum Pontiac-Buick in Marengo, IL. Dana Mecum's father's dealership and where Dana Mecum got his start selling cars before branching out and eventually starting up the Mecum Auction business.

Mine shows that Mecum purchased it using GMAC Wholesale credit (Sales Class A).

To the left of the Date Shipped it shows 2.5 HRS. patrick1234, anything like that on your PHS record?

HFR, any idea what that means?