# Engine code question



## 73GTO (Aug 25, 2007)

Can anyone tell me if the 1973 GTO Engine code "ZC" is exclusive to only that year and model vehicle, I have found no other reference after searching for over 4 years of the "ZC" engine being installed in any other Pontiac model. If anyone thinks it is not an exclusive engine to only the 1973 Pontiac GTO please offer up the proof for investigation by myself.

Thanks ,,, Please help me solve this mystery


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## abright52 (Dec 17, 2006)

Also used on V6, Manual Firebirds:

http://www.mprime.com/ProjectFirebird/FB11-specs.htm


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## 73GTO (Aug 25, 2007)

*Engine code*

OK, This is a 73, 455 engine, Looking for info applying to the 455 only. i'm trying to find out if the "ZC" 455 was used in any other models. I have found no evidence that it was. Thanks


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## 05GTO (Oct 6, 2004)

I am not finding any info on the letter code ZC for any pontiac engine including those 455's used in 73,


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## 73GTO (Aug 25, 2007)

*engine code*

I have one. Here's some GTO info from GTO Alley
http://www.gtoalley.com/engcodens.html

Year CID Casting Number
1973 455 485428

1973 Letter Code CID HP Trans 
ZC 455 250 Auto 

All these number match on my engine


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## 73GTO (Aug 25, 2007)

*Engine Code*

What do you think?


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## 05GTO (Oct 6, 2004)

That is a beautiful 67 Grand Prix,


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## GTO JUDGE (May 14, 2005)

73GTO said:


> What do you think?


*Absolutely GORGEOUS.... Been a long time since I seen a pic of one let alone in person.*


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## 73GTO (Aug 25, 2007)

Thanks for the compliments. There are three things I dig about this car (1) it has a complete GTO drive-train (2) The hide-away headlights which we all know was on the GTO as well (3) the tailights look like the GTO back-end. The car screams muscle just looking and listening to it.

You know, Maybe I should get a GTO - My brother-in-law will have his 69 convertable, #'s matching goat back this weekend from the paint shop, the engine was done last year. I"ll post some pics when I see it, I'm calling him now.

I still haven't found anymore information on the engine code though, Another little thing is there is no VIN# stamped by the timing cover like there should be. From everything I've read over the years there should be one there correct?


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## 05GTO (Oct 6, 2004)

You could look on the back of the block behind the #8 cylinder (passenger side) for the casting number, also there should be a 455 on the block by the fuel pump. The casting number for 455's in 73 was 485428 and 490132.


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## 73GTO (Aug 25, 2007)

I've got all the #'s off every nook and cranny. I did find the Vin# today. Is there any way I can run the Vin# other than through PHS?


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## 05GTO (Oct 6, 2004)

Does the engine VIN start with 23? If so replace the 2 with 2D37Y and that will be the cars VIN number that the engine came from. 

PHS is the only way I know of to find the information from these old pontiacs, I would try to find more info about the Grand Prix, more than likely that car may have had a 428.


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## 73GTO (Aug 25, 2007)

Yes it does start with 23, I'm sure the GP had a 428 in it prior to the 455, I'm trying to gather as much engine info as I can.

*"Does the engine VIN start with 23? If so replace the 2 with 2D37Y"*

I don't follow what you mean. 

If this is the VIN, 23A00001 What should I do?


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## 05GTO (Oct 6, 2004)

73GTO said:


> Yes it does start with 23, I'm sure the GP had a 428 in it prior to the 455, I'm trying to gather as much engine info as I can.
> 
> *"Does the engine VIN start with 23? If so replace the 2 with 2D37Y"*
> 
> ...


2D37Y3A100001

2= Pontiac
D= Lemans
37= 2 door hardtop
Y= 455
3= model year
A= Built in Atlanta
100001= Car vin serial number, replace with the last 6 digits on the engine vin number.


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## 73GTO (Aug 25, 2007)

I don't understand where the "D" comes from?

I just climbed out from under the car again for a closer inspection of the number. After the Plant designation letter, there are only 5 digits. I cleaned the area so that it looks brand new. Is this odd?


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## 73GTO (Aug 25, 2007)

*Engine*

New paint on a 69 Goat / Plus a Grandville


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## 73GTO (Aug 25, 2007)

Still confused. I'll be in touch , thanks


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## 05GTO (Oct 6, 2004)

73GTO said:


> I don't understand where the "D" comes from?
> 
> I just climbed out from under the car again for a closer inspection of the number. After the Plant designation letter, there are only 5 digits. I cleaned the area so that it looks brand new. Is this odd?


The D Series Number is the identifier for the (standard) Lemans model, the Lemans sport was identified with the letter F. The GTO did not have the seperate series number (as did the earlier years) for 1973 and was an option to the Lemans models. The PHS report will identify the car (or vin number) as being (from) a true GTO on the Build Sheet with a Sales Code of 341 which was for the GTO Option.

The VIN is 13 digits long and you should have 6 numbers after the letter that identifies the city where the car was built. You may be looking at the wrong number, the engine vin should be to the left of the timing belt cover just under the passenger head.


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## 73GTO (Aug 25, 2007)

Thanks for getting back to me. I looked again, to the left of the timing cover, It is very clear and clean, I will post a pic for you to see, (it has now started to rain) tomorrow. These are the numbers that are there,

23A16262 ,,,, I know there should be 6 numbers from what you've told me and what I looked up, but this is all there is, This really seems odd don't you think.

This is where I got the number,


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## 73GTO (Aug 25, 2007)

Ok, still looking for help witht he numbers. Maybe I'm getting confused. One more time for me please. Explain.

I just bought a dual quad setup - will arrive tomorrow.


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