Find answers to Frequently Asked Questions for First Generation Firebirds that have been asked and answered on FGF. Special thanks needs to be given to all the FGF members who took the time to respond to other member's questions.
Engine - Codes
Q: Vin, Body Tag, and Engine Code Information
Running the vin number and body tag number on oakmediacreations firebird page the production numbers of the vehicle didn’t match one another plus what do the codes on the engine stand for:
Block Casting numbers on R/F of engine (only numbers I can see)
GM4
Stamped numbers on the right front of engine block
508743
YJ
A: This is correct, these two numbers found on the body tag and the VIN will not match. The numbers on the VIN represent the Sequential Production Number. The numbers on the Body Tag represent the Unit Number or consecutive build number. The last tells in sequence when the car came off the assembly line. Again, the body tag number will not match the actual sequential VIN number.
Block Casting numbers on R/F of engine (only numbers I can see) GM4
I do not know what these represented on the block.
Stamped numbers on the right front of engine block
508743 = Motor Unit Number
YJ = 8 cyl, 326 cid, 250 hp, 9.2:1 comp. ratio, 2 bc carb, auto trans.
Sources: Firebird Red Book, Catalog of Firebird ID Numbers 1967-93, Pontiac Historic Services, Year One Catalog
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Content last modified: January 24, 2014 at 9:53 pm
Q: Engine Serial Number does NOT Match Vehicle Identification Number
I was told buy one of my local specialty wrecking yards that the engine serial number and the VIN number didn’t always match from the factory. I’m inclined to believe him. My 1968 convertible was built in Los Angles and it’s all original. Nowhere in my delivery documentation does the engine serial number appear, only the VIN and Body Tag data. My engine and VIN don’t match – not even close. What’s the truth here?
A: Short Answer:
* The VIN on the car should match the VIN on the Engine (68 & up)
* The Engine Unit (Serial) Number was a separate number stamped on the Engine. This number has nothing to do with the VIN and appears with the VIN on the Billing History.
So, you are correct when you say the Serial Number and VIN did not always match. Infact, they will NEVER match because they are different/separate numbers. If the VIN on the front of the Block matches the VIN on the Dash, that is the original correct engine for that car. You can also search for the B’Cast Sheet in the car, that will also ‘authenticate’ your car.
A: Engine ‘Serial’ Number (manifest number) has no connection whatsoever to the Vehicle Identification Number. This number was used within the Plant for sequencing. There is a VIN stamped on the block however that should match the VIN on the car. This is stamped on the front, lower face of the block next to the timing chain cover (way down low near the harmonic balancer). People have tried explaining the purpose of the Engine Serial Number yet, nothing official from PMD has ever surfaced explaining when it was stamped and for what exactly it was used for. My guess is that is was used by scheduling/sequencing in order to match a particular engine with a specific car. The VIN would have most likely been stamped on the engine just prior to going into the car.
While working on the 1967, 1968, and 1969 Firebird Registry, I have found that you can have two cars with very close VIN numbers and yet, their Engine Block Serial Numbers are hundreds (or even thousands) of numbers a part. The Engine Serial (Unit) Number can be found on the Broadcast Sheet and the Billing History Sheet. Once the car was built, only the VIN had any significance since the car, engine and trans (manual only) were tied together through it.
Here’s another clue about the Engine Unit Number…. Looking through Service Bulletins, if an engine issue is addressed, most everytime the Engine Unit Number is mentioned. Example: for the 1967 Firebird w/Ram Air, there were two types of Engines; the 1st Type was used up through Engine Unit Number 646615. The 2nd Type started at 646616. Another Bulletin addresses the issue of 1967 Cylinder Head Oil Return Passage Modifications. It lists those vehicles involved including the range of VIN numbers and the Engine Production Number involved. Based on these examples, I would say the Engine Serial (Unit, Production, Manifest) Number was stamped onto the block somewhere within the Engine Assembly Line (not the foundary) along with the Engine Usage or Application Code (Two-Letter). I say this because the Foundary did not assemble the engine and had no idea whether it was going into a GTO or Firebird and if it was to be a manual or automatic Engine. Once the Engine Assembly Line received the Block, scheduling would have given it a specific Usage Code (2-Letter) in order for the Line to install the correct components on the Engine. Perhaps the Engine Unit Number was stamped at this point as well (according to scheduling/sequencing). At some point following the Engine Assembly, the Engine Unit Number was ‘connected’ to a VIN in order for the Plant to know which engine to ‘pick’ (or schedule) for a specific car.
I doubt that 30yrs ago, the assembly plants were using the same sequencing (or “Just in Time”) delivery methods we use today however, I’m sure they did have some sort of scheduling/sequencing system. Also remember that the engine had a large white label with red letters attached over the two-letter code stamped on the front of the block. This was another aid in determining usage/application for a specific engine (much easier to read this white/red label than to squint to see the 2-letter stamped code). Anyhow, That’s my ‘long-winded’ opinion on the issue of Engine Unit Numbers.
A: I used to work at the GM assembly plant if Fremont, CA. Engines came fully assembled less optional accessories. I’m sure this was the case at the sister LA pant as well. When the engine s/n number was stamped I don’t know. But I do know that sometimes there were problems with engines after they were installed and were swapped out at the plant. Also, sometimes there were problems like more bodies than engines (remember Buick engines going into Chevys – it’s true!), and they would grab whatever engine they could find and throw it in to keep the line moving. For what it’s worth!
A: …Yes, Engine usually came to most Final Assembly Plants fully assembled. (Not always the case though). In addition to a Forging/Casting Plant, there was also an Engine Plant where they were assembled. I’d guess this is where the engine received its Serial Number stamp. This number was used by the Final Assembly Plant (for the vehicle) to coordinate scheduling/sequencing for the engine to body. No matter what the situation in the Plant, I seriously doubt that they would grab whatever engine they could to keep the line moving. Especially after ’67. Engines were sequenced with the body and were controlled for many reasons. The case of the Chevy/Buick engines was unique and different. Despite the mix of engines, all still had serial/VIN numbers stamped on them and they matched a specific car. It’s not like there was just this big batch of engines and a Line Operator going.. “eenie meenie minee moe….”
A: The VIN got stamped on the block starting in 1968. I have a 1968 Ram Air I, and the VIN on the block, just to the left (looking at the front of the engine) of the timing cover, matches the last 6 numbers of the VIN. This number can”t be seen unless you remove the lower radiator hose from the water pump housing, or if you get a mirror and shine a light down by the harmonic balancer, you can see it
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Content last modified: January 24, 2014 at 9:47 pm
Q: Decoding Engine, Carburetor, Manifolds
I know I had a reference to decode some of these numbers, but I have forgotten if it was a book or website. My engine has ‘YR’ and ‘33202’ stamped just to the left of the top of the water pump, and ’23N108627′ stamped below the water pump. The intake manifold has ‘E220’ cast into it and the exhaust manifold has ‘9796155’ cast into it. The numbers on the carb are 17054905 and just below, 2738. Would someone please tell me what these codes mean. Thanks.
A:
YR ….. This is the specific Engine Usage/Type Code
33202…. This is the Engine Unit Number
23N108627…. This is the partial VIN, unique to the car the engine came from
E220….. This is a Date Code (May 22 ’70 ?)
9796155… This is a Part/Casting Number
17054905…. This is the Usage Code for a Rochester Carb
2738….. This is the Build Date Code (273rd day of 1968 ?)
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Content last modified: January 24, 2014 at 9:46 pm
Q: Engine Codes
I am currently in the process of having my engine for my 1967 400 Convertible rebuilt. The mechanic has cross-referenced the (YD) code to a 1967 400, but it says it is a 2 barrell, and my engine has a 4 barrell. I am unable to find a cross reference for the engine code under the 1967 sectioin of this site. I do not see the letters referenced in this section. Can someone help me?
The code on the block is: 0081718 YD
Also stamped is: 20P105982
A: The 20P105982 is your clue to what that engine really came from. The first zero means it’s from a 1970 car, and the letter “P” means it was from a car built at the Pontiac assembly plant, where that year they were building full-sized cars like Catalina and Bonneville. The YD for that year indicates a 2 barrel 400, 290 gross HP from a Pontiac, meaning big car. Although the chart I have says a 10.0:1 compression ratio, it does not say what head cast numbers were used.
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Content last modified: January 24, 2014 at 9:41 pm
Q: 400 Engine Block Code for 1967
I’m trying to decipher a code cast into the block on my 1967 firebird. The code is located near to where the distributor fits into the block. I think it is the cast date of the block but I would like to know for sure. The code is 86133. (As best as I can tell).
I know this isn’t the sequential build number, (serial number), of the block since that is locate on the front on the block on the passenger side of the car.
I’d appreciate any information you can provide.
A: That is the blank block casting number. It’s like a part number. According to my info the whole number is 9786133. This denotes a 1967 400 cid block. I got the info from a book called Pontiac Muscle car performance 1955-1979 by Pete McCarthy
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Content last modified: January 24, 2014 at 9:41 pm
Q: Engine Unit Number Does Not Match
The engine unit number stamped on my 1968 does not match the Billing History but I know it is an original engine. The engine code is WK, and the number next to that is 205848, engine unit production number per the Firebird page Tech info and has no reference to VIN number. Then the “engine unit number isted on the PHS Billing history is 205818. Note the number varies in one number: 4 vs 1. Could this be a miss stamp or some type of mistake.
A: Engine Unit Number is the number stamped on the fron of the Block next to the Engine Code. Also found on the Billing History. These numbers should be the same. The Engine Unit Number and partial VIN were stamped on manually and were not as deep as the Code stamp. Also, there was not alot of quality assurance & certification back in 1968.
The Gang-Stamp Tool could have slipped during the strike causing a partial stamp. Wouldn’t doubt that a mis-stamp could have happened either. Considering the numbers you shared are so close, seems obvious they are one in the same… despite their seemingly different appearance. I wouldn’t lose any sleep over it. Who would believe that you had the wrong engine and it just happened to be 30 units different from the original ?
A: My guess is that the digit “4 ” is correct and that the digit”1″ stamped into your block is a weak stamping of the number “4”.Ive seen several weak stampings of production #s and VIN #s Some of which appeared to even skip a digit. This was actually a very weak stamping and had only a small portion of the number visable. Take a real close look, Im betting its a 4.
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Content last modified: January 24, 2014 at 9:42 pm
Q: Engine Code Confusion for 1969
I’m completely confused about the the engine serial # vs. the partial vin # on the engine….
A: In 1969, the partial VIN was stamped on the front, RH face of the Engine. It could also be found on Manual Transmissions in addition to the “hidden” partial VINs stamped onto the Body Shell. Besides the VIN plate attached to the upper RH Cowl (dash), there was also a Fisher Body Trim Tag attached to the RH Cowl (firewall).
Documentation for the 1969 Firebird (sequentially listed) consisted of:
1) Chassis Broadcast Copy (for engine/chassis Line Workers)
2) Body Broadcast Copy (for Trim & Final Line Workers)
3) Car Billing Invoice (for accounting)
4) Window Sticker (for dealer/customer)
5) Owner Protection Warranty Protecto-Plate
The VIN was used to identify the Vehicle Division, Assembly Plant, Body Style, Vehicle Series, Production Model Year, Engine Type (6cyl, V-8) and Sequential Unit Number. (NOTE: Vehicles were not always built completely sequentially per VIN) ((More on that later)). The VIN is found on all Documentation.
The Fisher Body Unit Number was used during the Scheduling Phase for both Fisher Body and the Final Assembly Plant. For 1969, this included Lordstown, Norwood and Van Nuys. Each plant used a different method for assigning this number. Despite what many people claim, this number was NOT entirely a Sequential Unit Number. Vehicles were built in batches; The VIN was assigned from a batch set of numbers. Build Scheduling was based on many factors and not simply on who ordered first. As with the VIN issue, the Body Unit Number requires a more in-depth explanation. ((coming soon to a web-site near you)). The Body Unit Number can be found on the Broadcast Copies, Protecto-Plate and the Window Sticker.
Starting in 1969, the Fisher Body Unit Number and Identification Number (as noted on the Broadcast Copy) were both the same numbers. On the Car Billing Invoice, there was another type of Identification Number used for accounting purposes only.
The Invoice also noted the “Dealer Order Number” (for accounting).
The Broadcast Copies also used a “Sequence Number” (3-digits). This was used for scheduling batch builds at Fisher Body. No sequential connection to any other numbers.
The Trim Tag Date Code refered to the Fisher Body Scheduled Build Date (week & month). This was for the “Body in White” (bare shell) and not the Final, fully assembled vehicle. The closest date for Final Assembly can be found on the Invoice. There were (3) different dates identified: – “Date Shipped”, “Date of Note”, “Date of Execution” The “Date Shipped” would usually be no later than a few days of when the vehicle actually left the Final Line Certification Buy-Off.
The Engine Unit Number for the 1969 Firebird (stamped on the RH front face of the Block) was used during Engine Assembly (Sub & Final) and for the Engine Installation Sequence at the Final Assembly Plant. The Engine Unit Number can be found on the Protecto-Plate and the Chassis Broadcast Copy (not Body Broadcast). Starting in 1969, the Engine Unit Number was not used on the Car Invoice. Once the Vehicle left Final Assembly, the only purpose for the Engine Unit Number was for Warranty related work which is why it was stamped onto the Protecto-Plate. The Accounting Dept. used the VIN and their own “Identification Number” found only on the Car Billing Invoice (microfiche files from PMD). This Number was used for billing between the Assembly Plant, Accounting and the Destination Dealer.
In order to verify a correct numbers matching 1969 Firebird, the VIN on the Dash must match the VIN on the front of the Engine Block. Unless you have the original Protecto-Plate, the Engine Unit Number cannot be verified since it was not related to any other vehicle number.
Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.
Content last modified: January 24, 2014 at 9:42 pm
Q: Engine Date Code for 1967
I have confirmed that the engine number on my 1967 is: 415371 is the motor unit number, YT is the engine code: 400 AT with AIR, and the number on the distributor pad, is actually 9786133 and denotes a 1967 400 cid block.
What I am curious about is if there is any sort of build date number located anywhere on the block or encoded in the motor unit number itself. The reason I am interested is that I would like to find another 1967 YT motor for my car. The build date on my car is 03 B, which translates into the second week of March. Since GM didn’t start stamping the engine blocks with the car’s VIN until 1968, all I need to do is locate a 1967 YT block which has a build date of prior to the second week in March, providing the blocks have/had any build dates associated with them in the first place.
So, if I am going to go through the hassle and expense of finding another YT block, I need make sure that the block I do find would actually be date correct for my car.
A: I got the following email reply to a simliliar post I did to rec.autos.antique. It explains where the date code is, and how to decode it. I checked on my motor and sure enough, my date code is B157, which is a build date of 2/15/67. Which makes perfect sense if the build date of the car was the second week of March. So, I thought I would share the information with the list:
You probably saw the build date code and just didn’t recognize it. On the top surface around the distributor hole you will find a code that starts with a letter and has 3 digits. The letter indicates the month, the next two digits are the day, the last digit is the last digit of the year. In your case a correct date code might be B077. This would read “B” = February, “07” = 7th day of the month, “7” = 1967.
The only time this gets fuzzy is with the use of the letter “i”. Some factories skipped the letter so that it would not be confused with a “1”. However this is not a perfect rule, some factories did use it but not all. The other problem you will have is that since your vehicle was built early in 1967 there are a lot fewer motors to choose from as Pontiac just moved from the 389 to the 400 in ’67. To be totally authentic you need a date code within about three months of your build date. Engines weren’t left laying around any longer than that and a judge in the really picky levels of competition will count off for anything outside of that.
A: Check out the date code near the distributor. It’s 4 digits, starts with a letter and 3 numbers. The letter is the month A=Jan, B=Feb…the last digit is the year. Starting in sometime in Sept the engine would be for the next model year. If you have any questions, post the code.
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Content last modified: January 24, 2014 at 9:43 pm
Q: 350 HO Codes for 1968
What were the possible options and codes on my:
1968 Firebird 350 H.O.
L-76 H.O. Engine, 4Bbl Carb, Dual Exhaust, “H.O.” Side Stripes
A:
Engine:
350 H.O. Man. Trans. “WK” 320 H.P. 10.5:1 Compr.
350 H.O. Auto. Trans. “YM” 320 H.P. 10.5:1 Compr.
Trans:
3-Spd. Standard (C/S) Saginaw “RJ”
3-Spd. Standard (F/S) Dearborn “DB”
4-Spd Optional Muncie “FX”
2-Spd Auto ST-300 “MB”
2-Spd Auto (w/A/C) ST-300 “MC”
Cylinder Heads: “18”
Carburetor: M.T. 7028269 A.T. 7028266
Intake manifold: (same as all 4Bbl) 9790140
Exhaust Manifolds: (same as Std. & 400) 9794320RH/9777755LH)
Distributor: M.T. 1111447 A.T. 1111282
*There were 2,087 400 H.O. Firebirds made in 1968. I’d guess that there were close to that for the 350, perhaps less.
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Content last modified: January 24, 2014 at 9:44 pm
Content last modified: September 15, 2023 at 11:15 am