[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

[johnta1]

I'd say it is ZC then.
And the VIN to your car is correct.
(and automatic)

[johnta1]

BTW, what is the date code on the cowl tag?
Or the PHS shipped date?

It sounds like it is an early build, possibly before the EGR change?

[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

[skunkwerks]

looks Legit to me. You can see the circular machine broach marks from the factory process. Stamps are all legit except for the 5 larger ones. Who ever put the bondo on was not able to find that 2 digit stamp code ZC and thought it was incorrect and tried to correct it. The 5 bigger stamps vertically are an engine rebuilders stamp to keep track of the block while in their facility. I have a couple of engine blocks with big stamp numbers on front pad from rebuilders. If I understand the original posting correctly. JMO

[Held for Ransom]

I agree with skunkwerks that the engine was rebuilt, hence the larger stamped digits.

Engine was too early for the changeover to the new EGR system (EPA forced Pontiac to have a real working system) and that happened around Mar. 15th.

[patrick1234]

Originally Posted by Held for Ransom

I agree with skunkwerks that the engine was rebuilt, hence the larger stamped digits.

Engine was too early for the changeover to the new EGR system (EPA forced Pontiac to have a real working system) and that happened around Mar. 15th.

Was this the old EGR system? I was thinking on disabling it. I havn't inspected it yet to see how it works, does it not pass gas with no vacuum? I included the date code of the intake.

[unruhjonny]

Incase there is anything left to confusion, please allow my contribution;
I was concerned at the quote below:

thin layer of bondo came off with my XL stamping.

As the other guys said, everything looks good to me - but it does look like someone attempted(?) to scratch something infront of the EUN - granted, I don't know all the in's & out's for Engine Unit Numbers, so maybe what I'm seeing as a scratch is the first digit...

[Held for Ransom]

Originally Posted by patrick1234

Was this the old EGR system? I was thinking on disabling it. I havn't inspected it yet to see how it works, does it not pass gas with no vacuum? I included the date code of the intake.

That is the early system using the 2nd intake of the 1973 model year. The timing system of the distributor retarding wasn't really up to emission standards and had to be revamped.
http://www.forums.maxperformanceinc....d.php?t=806646