Factory Stage1 Identification

This page starts with one thought: never say never when it comes to these cars. So much information has come to light about these cars in recent years and the information contained in this page is believed to be as accurate as possible. If someone has a question, update, or correction to any information contained on this webpage, please E-Mail Me: marco@stage1registry.com.

This webpage is a community effort, a 'knowledge dump', from many people who were willing to share their time and knowledge so we can all be more educated about these cars. Hopefully the information contained on this webpage will help you document your Buick GS. This webpage will be updated with any additional information or corrections as needed.

Disclaimer:

Different Types of Buick Build Sheets
POBF sheet (1969-1971 Flint built) Please click to enlarge	'Other' (GMAD) Build Sheet Please click to enlarge

1969-1970 Motor Identification (E1)

1971-1974 Motor Identification (E2)

1975-1976 Motor Identification (E3)

Transmission VIN Identification (T1)

Transmission Code Identification (T2) BB Trans Tag

Transmission Code Identification (T3) OW Trans Tag - 1971 Only

• From a performance aspect, the stage1 option consisted of larger valves in the heads (1970-up 455 engines only: intake valves increased from 2.00 to 2.125 and exhaust valves increased from 1.625 to 1.75), stiffer valve springs (used a dual spring setup), rejetted carburetor, recurved distributor, special high-lift camshaft, high-volume fuel pump, different oil pump spring, bigger oil pickup tube diameter (for 1969-1970 only, starting in 1971 all 455s had a 5/8'' OD tube), heavy duty cooling (7 blade fan), special TH400 transmission (if so equipped - see below for details), and a positive traction (posi) rear. A 10-bolt posi rear was standard for all years, with rear gear ratios of 3.64:1 for non A/C cars and 3.42:1 for A/C cars in 1969 and 1970. Starting in 1971, all stage1 Gran Sports received 3.42:1 rear gear ratios. While not the norm, it was possible for cars built at a GMAD plant (like Framingham MA) to have received a 12 bolt rear from the factory. If a rear was needed to keep the assembly line moving, the line workers used what was available.
  
  
• From an appearance aspect, all factory stage1 Gran Sports came with chrome valve covers, nuts, and wire loom studs. 1969 model year cars had valve stickers which stated '400-4 Stage 1' and contained 'Stage 1' hood emblems alongside the ram air scoops. 1970 - 1974 model year cars had an air cleaner decal which stated 'Stage 1'. 1970-1972 Gran Sport models had stage 1 badges on the fender under the 'GS' emblems, while 1973-1974 models had stage1 badges at the front of the fenders.
  
  
• Engine production codes for all years are two digits and are stamped between the #5 and #7 spark plugs (drivers side rear), on the surface of the block just below the head (figure E1). The second digit must be an 'S'. The engine VIN stamping location varies from year to year, and each year's location is also identified figure E1.
  
  
• Automatic transmissions have a tag on the passenger side (figure T2) that contains the code identifying the transmission application. Stage1 GSs came with heavy duty transmissions with a 2.48 first gear. ALL had (or were supposed to have) steel flat washers (instead of wave type) and 6 plate clutch packs (instead of 5 plates with wave washers). These types of transmissions were referred to as a 'Cadillac sprag' transmissions, and were used in high torque applications. The servo spring was different, in addition to the valve body pressure. The following was taken from a post on www.v8buick.com by TH400 expert Mark DeConti

  "The 70 BB Stage 1 was unique. The later valve bodies were not setup like it, though close. Not all 70 Stage 1 BB's had the 6 clutch drum, it depended on the build date as it was used after a certain point. A lot of 70 BA's had the 6 clutch drum too. The BB's used a different direct piston which improved the 3 gear shift. The 70 BA valve body is VERY close in design to the 70 BB and only a spring in the 1-2 accumulator valve needs to be removed to make it the same. No waved steel plates were used in the 2nd and 3rd gear clutch packs on the Stage 1 trans, and the 3rd gear valve body accumulator spring was softer to firm up the shift. The governor was setup to shift at approx. 5500 rpm and was specific to 1970 BB only (some model of Pontiac and maybe Olds used it too). Later governors were ok, but closer to 5200 rpm. The valve body separator plate has larger holes in places to increase pressure to the clutches. Am pretty sure that 70 was by itself and 71-72 was different."
  ...............................................................
  "On the 70 models, higher rpm governor. no wave plates in 2nd and 3rd clutch packs and the 3rd clutch piston was different on 6 clutch pack units. Valve bodys were setup for firmer shifts (1-2 accumulator valve spring removed and s ofter 2-3 accumulator) and shift plates were different. Some of these mods were carried over to 71 and later, but not as extensive as 70. Also, not all 70 Stage 1 trans had 6 clutch 3rd packs. The 5 clutch packs were used until a certain build date in both. Then both used 6 clutch packs with the Stage 1 units getting the special piston. At least this is what I have found on the ones I have worked on."

  
  
• Manual transmissions do not have any significant codes to prove it's a factory stage1 Gran Sport. The VIN is stamped vertically on the passenger side of the transmission (figure T1). The Muncie stamping is right below this. The stamping can be decoded at 5speeds.com, and the deciphered date should be consistent with the build date/model year of the car.
  
  
• Stage1 heads do not have a special casting number over non-stage1 heads. You need to remove the head and look at the valves. Stage 1 heads contain valves which 'almost' touch. Here are pictures of standard valves versus stage1 valves. Pictures courtesy of George Nenadovich at BuickPerformanceClub.com.
  

Here are the specific components to the 1969 stage1 package. Please click the picture to enlarge.

• If the engine is original, the 'Engine Serial Number' (figure E1) should read 9 digits - a '4' (for Buick), followed by the last 8 digits of the VIN. If the VIN is 446379H100001, the engine serial number would be 49H100001.
• The 'Engine Production Code Number' (figure E1) will depict the engine option - 'RS' is Stage1. A complete list of 'Engine Production Code Numbers' can be found on Buicks.net
• Block/Head casting numbers, in addition to carburetor/distributor numbers can be found Here.

• If the transmission is original, the 'Transmission Serial Number' (figure T1) should read 9 digits - a '4' (for Buick), followed by the last 8 digits of the VIN. If the VIN is 446379H100001, the transmission serial number would be 49H100001.
• If a TH400, the 'Transmission Code' (figure T2) will depict the transmission type - 'BB' is Stage1 - just make sure the serial number (figure T1) matches the VIN. A complete list of Buick TH400 transmission codes can be found on Buicks.net
• If a manual transmission, there are no significant codes to prove the stage1 option, but the Muncie stampings can be can be decoded Here

Here are the specific components to the 1970 stage1 package. Please click the picture to enlarge.

• If the engine is original, the 'Engine Serial Number' (figure E1) should read 9 digits - a '4' (for Buick), followed by the last 8 digits of the VIN. If the VIN is 446370H100001, the engine serial number would be 40H100001. For cars built later in the model year, it is possible for the engine serial number to be located on the front of the block as depicted in figure E2
• The 'Engine Production Code Number' (figure E1) will depict the engine option - 'SS' is Stage1. A complete list of 'Engine Production Code Numbers' can be found on Buicks.net
• Block/Head casting numbers, in addition to carburetor/distributor numbers can be found Here.

• If the transmission is original, the 'Transmission Serial Number' (figure T1) should read 9 digits - a '4' (for Buick), followed by the last 8 digits of the VIN. If the VIN is 446370H100001, the transmission serial number would be 40H100001.
• If a TH400, the 'Transmission Code' (figure T2) will depict the transmission type - 'BB' is Stage1 - just make sure the serial number (figure T1) matches the VIN. A complete list of Buick TH400 transmission codes can be found on Buicks.net
• If a manual transmission, there are no significant codes to prove the stage1 option, but the Muncie stampings can be can be decoded Here

• All 81 1971 factory Gran Sport convertible Stage1 cars were ONLY built in Flint MI (plant code 'H'), meaning the VIN must start with 434671H.
• The 801 hardtops were built in one of three plants -
  - Flint MI (VIN starting with 434371H - 612 cars)
  - Framingham MA (VIN starting with 434371G - 56 cars)
  - Fremont CA (VIN starting with 434371Z - 133 cars)

• If the engine is original, the 'Engine Serial Number' (figure E2) should read 9 digits - a '4' (for Buick), followed by the last 8 digits of the VIN. If the VIN is 434371H100001, the engine serial number would be 41H100001. It is also possible for the engine serial stamping to be in the same location on the passenger side of the block. Remember, never say never.
• The 'Engine Production Code Number' (figure E1) will depict the engine option - 'TS' is Stage1. A complete list of 'Engine Production Code Numbers' can be found on Buicks.net
• Block/Head casting numbers, in addition to carburetor/distributor numbers can be found Here.

• If the transmission is original, the 'Transmission Serial Number' (figure T1) should read 9 digits - a '4' (for Buick), followed by the last 8 digits of the VIN. If the VIN is 434371H100001, the transmission serial number would be 41H100001.
• If a TH400, the 'Transmission Code' (figure T2) will depict the transmission type - 'BB' or 'OW' is Stage1 - just make sure the serial number (figure T1) matches the VIN. A complete list of Buick TH400 transmission codes can be found on Buicks.net
• If a manual transmission, there are no significant codes to prove the stage1 option, but the Muncie stampings can be can be decoded Here

• All 81 1972 factory Gran Sport convertible Stage1 cars were ONLY built in Flint MI (plant code 'H'), meaning the VIN must start with 4G67V2H.
• The 728 hardtops were built in one of three plants -
  - Flint MI (VIN starting with 4G37V2H - 463 cars)
  - Framingham MA (VIN starting with 4G37V2G - 147 cars)
  - Fremont CA (VIN starting with 4G37V2Z - 118 cars)

• If the engine is original, the 'Engine Serial Number' (figure E2) should read 9 digits - a '4' (for Buick), followed by the last 8 digits of the VIN. If the VIN is 4G37V2H100001, the engine serial number would be 42H100001. It is also possible for the engine serial stamping to be in the same location on the passenger side of the block. Remember, never say never.
• The 'Engine Production Code Number' (figure E1) will depict the engine option - 'WS' is Stage1. A complete list of 'Engine Production Code Numbers' can be found on Buicks.net
• Block/Head casting numbers, in addition to carburetor/distributor numbers can be found Here.

• If the transmission is original, the 'Transmission Serial Number' (figure T1) should read 9 digits - a '4' (for Buick), followed by the last 8 digits of the VIN. If the VIN is 4G37V2H100001, the transmission serial number would be 42H100001.
• If a TH400, the 'Transmission Code' (figure T2) will depict the transmission type - 'BB' is Stage1 - just make sure the serial number (figure T1) matches the VIN. A complete list of Buick TH400 transmission codes can be found on Buicks.net
• If a manual transmission, there are no significant codes to prove the stage1 option, but the Muncie stampings can be can be decoded Here

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