INFO GUIDE: 1966 Pontiac GTO (Coupe, Hardtop & Convertible)

The 1966 Pontiac GTO had the following external features, distinguishing itself from the Tempest and Le Mans line as well as other GTO models. Where a feature is unique to the 1966 model, or shared with other models, this has been noted.

• Available in three body styles:
  • Hardtop (no B-pillar).
  • Sports coupe (Coupe with B pillar).
  • Convertible.
• Fitted standard with steel 14 inch X 6 inch steel wheels for the entry level model. These were available painted several colors as outlined in the paints section of this guide).
• Optionally fitted with the 14 inch X 6 inch ‘Rally I’ wheels. The wheels were painted ‘Rinshed-Mason’ Silver (Code E28C009), and were the same as the wheels used on the previous model year, however, the area around the wheel hub studs was black.
• Wheels were fitted standard with Redline Firestone F70 x 14 tyres.
• Front quarter rocker panel “GTO” badges noting the engine size (located at the rear of the front mudguard), held on by cadmium clips.
• Aluminium front grille frame featuring a square patterned plastic black grille (the use of plastic was an industry first).
• ‘Louver’ style rear tail lights.
• In contrast to later models, the 1966 GTO featured chrome work that followed the contours of the rear boot, and connected with the same contours moulded into the rear bumper.
• “Pontiac” badge spelt out between the rear tail lights.
• “GTO” badge featured on the left side of the front grille.
• Front hood scoop.
• Several additional aesthetic options were available for the 1966 model. See the options section of this guide for further details.
• Non-factory ‘Hurst’ options were also available on the 1966 model, including unique mag wheels. Note, however, these were never an original equipment wheel for the 1966 GTO because they did not meet GM’s weight guidelines, but were nonetheless a popular add on. Hurst equipment was generally supplied with a badge, explaining those seen on many GTOs.

The 1966 Pontiac GTO had the following interior features listed below. Many interior features may have been optional, and have therefore been outlined in section 10 of this guide.

• “GTO” badge featured on the passenger side dashboard and on the door cards.
• Timber veneer instrument cluster surround with four instrument dials (left to right): Fuel gauge/battery, speedo (120 MPH), tacho (5000 redline), water temp/oil pressure.
• “LeMans Deluxe” steering wheel was fitted standard. A Custom sports steering wheel was an option. Both wheels had a Pontiac badge on the centre boss and are demonstrated in the images.
• A white or black gear knob with the gear pattern in-laid on the knob was applied. A “Hurst” shifter mechanism and arm was also a period aftermarket item commonly applied to the 1966 GTO.
• Various interior colors were available on the 1966 GTO, which have been summarised in the below table for the various sections of the interior.
• The selected interior color will determine the color applied to the Dashboard, pillars, seats, roof lining and carpets (with the exception of Parchment, which featured Black carpets).
• The above interior codes will be located on the vehicle data plate, in the engine bay (see images).
• If the interior code has a “B” at the end of its sequence, this indicates bucket seats were installed. (e.g., “219-B”).
• Where the data plate has a hole punched into it (see example in images), this means that the vehicle was factory equipped with a shoulder harness.

Interior vinyl trim codes (60° gloss) (seats, door cards):

*Parchment interior came with black carpet

Upper instrument panel colors (0° gloss)

The available paint colors for the 1966 Pontiac GTO are outlined in the table below. A sample of each of the paint colors has been given in the attached images. Note, the engine bay in all cars (firewall and inner guards) was always finished in ‘Chassis Black’ (no longer manufactured by GM). This is reportedly a close match for PPG (Specialty) ST1202 paint. A GTOs paint code is located on the vehicle’s data plate in the engine bay, as described in the attached images.

Body Paint:

Wheel Paint:

Engine block paint:

The 1966 GTO had three color options for the vinyl hard top, and five color options for the convertible top. The relevant codes for the original colors can be found on the vehicles data plate in the engine bay, next to but separated from the paint code with a hiphen. See the attached images for further details.

1966 GTO vinyl top colors and codes:

1966 GTO convertible top colors and codes:

The 1966 Pontiac GTO will have a 13 digit chassis number / VIN which can be decoded per the following table:

Example: “242376B123456” = 1966 Pontiac GTO hard top built in Baltimore

Chassis number / VIN location:

The chassis number should appear in several locations on a 1966 GTO. These locations as described below, have been outlined in the attached images.

1. Embossed on the chassis plate, riveted to the front left door hinge panel with rosette rivets. (This is one long number which includes the chassis prefix and the unique vehicle production number as described above).
2. Embossed on the vehicle's data plate, riveted on the left side firewall/bulkhead, behind the brake booster. (Note, this plate contains only the first 5 digits of the chassis prefix, is preceded by the number "66", and a 3 digit ‘assembly plant’ code is applied. This plate does not contain the vehicle's unique production number matching that of the chassis plate.
3. Partial VIN may be stamped into various body panels of the car (such as on the firewall near the heater blower / AC hose, near the trunk lid seal, or on the driver’s side B-pillar). Pontiac did not stamp these areas in all production facilities.
4. The VIN should also be stamped into the engine block if the vehicle has its original engine (see engine number section of this guide for further details).
5. The VIN/ should also be stamped into the top of the vehicle's left rear chassis (frame), just behind the rear wheel where the frame goes over the axle. The body will need to be removed from the car to view this.

The 1966 Pontiac GTO’s data plate provides a substantial amount of information about the car. The meanings of the various codes labelled in the attached images are outlined below.

Note, the 66 GTO has two possible data plate formats, which we have labelled “Data Plate Type 1” & “Data Plate Type 2” accordingly.

Engine block serial number:

The 1966 GTO was fitted with a 389 CI Block, which should have a 6 digit serial number/VIN in three locations:

1. Front of the block.
2. Passenger side of the block.
3. Bottom of the block near the timing chain cover.

These locations are further described in the attached images. The block serial number should match the Chassis number found on the Chassis plate in order to qualify as a ‘matching numbers’ car. 

Engine type code:

The engine code confirms the engine's specifications in terms of power, transmission, and carburettor system. This is a 2 letter code, located on the front of the engine block, below the right side cylinder head. The engine serial number is stamped above this engine block code. The table below outlines the various applicable codes and associated engine types:

Engine Date Code:

The date code consists of 3 or 4 characters. Character 1 = month, Character 2/3 = day, Last character = year. The date code is found at the back of the engine block just below cylinder 8, as shown in the images. 

The following table outlines the month codes. Note, Code L refers to December 1965, as December 66 engines were being built for the 67 model GTO. 

E.g. C146 = March 14 1966

Engine Casting Code:

​The casting code is a code specific to the vehicle's year. The 1966 Pontiac GTO's 389Ci block should have the number 9778789 cast on the distributor Pad. See attached images for a better description of this location.

Engine Displacement Identification:

Unlike other V8 blocks produced by Pontiac during the 1960s, there are no 389 numbers cast anywhere on the block. Instead, to identify a 389 block, look for a notch on the passenger side deck where the block meets the head. See images for a better description of this identifier.

The 1966 Pontiac GTO had the following mechanical features:

• The 1966 GTO was available with a 4 barrel Rochester carburettor, fitted to the 389CI block with varying power outputs from 335 to 360HP depending on the optioned engine configuration (see Engine codes section of this guide).
• The 1966 GTO featured a revised Tri-Power carburettor (is Tri Power the brand?). You need to lookn into this more. I think Tri-Power was actually a reference to the cars having Triple Rochester carburetters?
• A Ram Air 389CI engine was released putting out the highest power of 360HP. This had a redesigned camshaft and valve springs.
• Aavailable in a 3 speed auto or 4 speed manual transmission.
• Varying axle ratios were featured on the various gearbox and engine types per the below table. The differential ratio is stamped on the passenger side axle tube.
• 14” X 6” Rally 1 wheels were featured as an option on the 1966 GTO along with the standard 14” X 6” stamped steel wheels.
• In the 1966 year model the GTO only came with 4 wheel 9.5 inch drum brakes. Disk brakes were not an available option.
• Polished aluminium rocker covers

Differential Ratios:

The 1966 Pontiac GTO was available with a large number of options, which we will endeavour to provide examples of. A full chart of options to be provided in this section shortly. In the meantime, please refer to the Collector's Originality Guide - Pontiac GTO 1964 - 1974, available through Google books.

The following sources, among input from many enthusiasts, have contributed to the creation of this page. If you have any further information you believe can be added, please let us know by contacting us or commenting below.

www.classicregister.com

http://www.gtoforum.com

Pontiac GTO Restoration Guide (Book) by Paul Zazarine

https://en.wikipedia.org/wiki/Pontiac_GTO#1966

http://www.pontiacdiy.com

Collector’s Originality Guide Pontiac GTO 1964-1974 (Book)

www.hemmings.com

www.Classiccars.com

www.oldride.com

www.myclassicgarage.com

www.pontiachunters.com