# Engine code question



## Everest (Feb 23, 2021)

Hello everyone,
I have a 66 and the PHS documentation has the engine build stamped for a WS engine. The block that is in there is coded as 475520YW. I can’t find much info about this particular engine block and was hoping some of you smarter individuals would know more about that stamp.


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## BLK69JUDGE (Jun 10, 2010)

Wallace Racing - Engine Code Charts


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## Everest (Feb 23, 2021)

Thanks I’ve seen this chart before but couldn’t find the damn thing anywhere even in search.


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## Sport Lemans (Apr 7, 2020)

We need to know what year the block is to figure out which YW engine you have. If it is a 1966, it is a 325hp 389 from a big car. Unfortunately, It could also be a 180hp 400 from a 1978 wagon. Get us the block stamp or a date stamp and we can help.


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## Everest (Feb 23, 2021)

Sport Lemans said:


> We need to know what year the block is to figure out which YW engine you have. If it is a 1966, it is a 325hp 389 from a big car. Unfortunately, It could also be a 180hp 400 from a 1978 wagon. Get us the block stamp or a date stamp and we can help.


Thanks, but I got it figured out. It’s a 325hp 389.


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## SimonKelly (Jun 25, 2020)

wow, that is nice, how did you find it all?


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## BearGFR (Aug 25, 2008)

Everest said:


> Hello everyone,
> I have a 66 and the PHS documentation has the engine build stamped for a WS engine. The block that is in there is coded as 475520YW. I can’t find much info about this particular engine block and was hoping some of you smarter individuals would know more about that stamp.


There's a sequence of steps to use in getting a positive ID on any Pontiac, and the order matters.

1) Start with the block date code. The ones I'm familiar with are located on the top rear of the block, in the center, near the distributor. It will be 4 characters: 1 alpha followed by 2 numerics. MDDY where A=January, B=Feburary, etc. DD: day of the month, Y last digit of the year. You have to get the date first because all the other codes used in the process were sometimes reused in more than one year and the same code could mean different things in different years. To translate the date code into a "year model", you have to remember that the engine foundry would begin casting parts for the next model year at about mid year (the exact date varied and I don't know of any sources that have the exact dates pinned down). The various web sites with reference information can be helpful in determining all the various locations on the engine parts where the codes might be. The code locations too changed over the years.

2) Once you know the model year, next stop is the block casting number. On my '69 400 with date code K278: (November 27, 1968 - so a mid production model year 1969 block) for example the casting number is 9790071 and it's located on top of the transmission mounting pad down below the passenger side head. This code will tell you if you've got a 400, 455, 389, etc. and in some cases, but not always, which flavor. There were different casting codes in '69 for a vanilla 400 like mine and the Ram Air IV variety.

3) Two-character 'engine' stamp on the front passenger side just below the deck. Once you know the model year and the engine, this code tells you what kind of car it was originally installed in and also some information about how it was equipped - i.e. carb, transmission, cam, etc.

4) Partial VIN (1968 and later only) - stamped into the passenger side front of the block, down low, adjacent to the timing cover. Ties the block to the VIN of the original car.

5) Engine Unit/Sequence Number (475520 in your case) - next to the code in 3) above. This is sort of a sequence number that was assigned at the time the car was built and was another way to tie the engine to the car. It's not really of much use without other records that were kept at build time and I think might appear on the build sheet if you have it. PHS has >some< of these available, but not all.

Sometimes you may find an "SR" designation on a block in addition to the other codes. This means "Service Replacement" and usually means that at some point the original engine was replaced, perhaps under warranty, by a dealer. It might also mean that someone bought a different engine through an official OEM Pontiac parts source/dealer and put it in the car. 

Bear


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## O52 (Jan 27, 2019)

Minor correction Bear,
The EUN has nothing to with any particular car. It is a sequential number stamped at the same time as the engine code at the Pontiac engine plant when the engine was built for the model year. 
Several individuals have created data sheets by using the EUN to determine when the actual engine build took place as compared to other engines. A low EUN would indicate an early build. 
Pontiac used the EUN for warranty purposes and for engine recall/updates.


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