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With the following information we can tell you exactly where your engine came from:

Block Casting Code Number
Date
Engine ID Code

From Wallace Racing website

Pontiac used the same codes on different year blocks.To differentiate them it will have to be determined what year the block is.
Next to the distributor hole there is a casting number that has a letter with 2 or 3 numbers. The letter is the month of manufacture- A=Jan. B=Feb,etc.
The next number or two is the day,
The most important is the last number, it is the year of Manufacture it is not always the model year, as most blocks are cast a few months before the car is made
.



65C23A41-84B7-498F-B088-DBBB013D5380.png



Then the engine code below the right side cylinder head.

BDC2DDC2-DC38-4DAC-9EEF-E7F4C9F076AA_4_5005_c.jpeg
 

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Discussion Starter #3 (Edited)
Thanks O52. Those numbers aren't that easy to get to. I'll see if I can get them. I think the intake casting number is for a 1970 400 ci engine.
The Rochester Quadrajet carb # is 7028268 which belongs to a 1968 400/400 H.O. Given those 2 things, I'm thinking it's a 400 ci engine. I installed a HEI distributor and got the car running. The carb is bad, it won't idle and needs to be replaced or rebuilt.
 

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‘65 GTO, 400ci, tri-power, 4spd,
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Thanks O52. Those numbers aren't that easy to get to. I'll see if can get them. I think the intake casting number is for a 1970 400 ci engine.
The Rochester Quadrajet carb # is 7028268 which belongs to a 1968 400/400 H.O. I installed a HEI distributor and got the car running. The carb is bad, it won't idle and needs to be replaced or rebuilt. Given those 2 things, I'm thinking it's a 400 ci engine.
the two letter engine code is located on the front passenger side of the block, but from your photos it looks to be pretty heavily painted over, so you might have to scrape it off a bit to see it better. With that, along with the casting number found on the back of the block by the distributer, you can look up the codes on this website to determine year and specs...

 

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66_Lemans. You’ve probably heard by now that Pontiac doesn’t have a Big Block or a Small Block engine. External dimensions pretty much stayed the same from the 50’s till the last day of production. This means that Pontiacs have unparalleled “swappability” of heads, blocks, manifolds, etc.

To find out what you have, really, you need to check the engine casting number by the distributor AND the head casting numbers on top of the center two exhaust ports.

Pontiacs left the factory with (essentially) flat top pistons, so compression ratio (CR) is determined by the cylinder head combustion chamber volume and the displacement of the short block.

Factory parts can be used to build engines with a CR from 6:1 to 14:1. A 1967 HO 326 was 250 HP; a 1975 455 was 200 HP! The biggest difference between 1967 and 1975 was Compression Ratio.

So, run your numbers and see what you have!
 

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Discussion Starter #6
66_Lemans. You’ve probably heard by now that Pontiac doesn’t have a Big Block or a Small Block engine. External dimensions pretty much stayed the same from the 50’s till the last day of production. This means that Pontiacs have unparalleled “swappability” of heads, blocks, manifolds, etc.

To find out what you have, really, you need to check the engine casting number by the distributor AND the head casting numbers on top of the center two exhaust ports.

Pontiacs left the factory with (essentially) flat top pistons, so compression ratio (CR) is determined by the cylinder head combustion chamber volume and the displacement of the short block.

Factory parts can be used to build engines with a CR from 6:1 to 14:1. A 1967 HO 326 was 250 HP; a 1975 455 was 200 HP! The biggest difference between 1967 and 1975 was Compression Ratio.

So, run your numbers and see what you have!
Those numbers aren't easy to access or read. I will try again. TY
 
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