By: Patrick Smith
Although the Y code reference is tied to the fifth position of the vehicle identification number (VIN) for 1972, the engine did exist the year before in 1971.GTO was still a separate series and GM wasn't using the VIN to identify drive trains then. There is one more important difference between 1971 and 1972 base 455 engines. The method of horsepower rating changed during that time. In 1971 GM lowered the compression ratio of their engines so they could operate on regular fuel in preparation for a future use of unleaded gasoline. GM did this by raising the combustion chamber volume. Horsepower for the base 455 engine was 260 horsepower in 1971. Then in 1972, a switch to the SAE standard of horsepower rating was made where the actual horsepower was defined as the engine was hooked up to the chassis with the power draining accessories in place. The base 455 four barrel now stood at 250 horsepower. Otherwise very little had changed between 1971 and 1972.
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| The 1972 Y code GTO shown in Castillian Bronze with black vinyl roof and duck tail spoiler options. |
We have a brochure page depicting in a Fitz and Van illustration how a Y code GTO appeared if ordered. This is sadly, a dream illustration as one option shown wasn't available after a few weeks of production, The duck tail spoiler mold broke very early and Pontiac didn't repair it, Only about 4 cars got duck tail spoilers. Three were LeMans and one was a GTO 400 hardtop. Notice that the decal call outs are present on the rear quarter panel of this car with 455 CID in white. The front fender panels are clean of any decals and die cast badges as are the rocker panels. At the brochure level at least, a Y code GTO used decal call outs only. To date, the only cars using the die cast fender emblems were LeMans cars with either Y or X code 455 engines.
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Shown here is a restored 1972 455 HO GTO quarter panel decal placement. Remember that on the assembly line,
consistency was sometime over ruled by efficiency. Even if there were decal transfer film marker overlays showing where
to place the decal before lifting backing paper, some workers just slapped them on fast, |
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| The GTO portion of quarter panel decal is shown here at the top of the rear tail lamp lens and 1 and half inches inboard. |
Some restorers asked recently about the proper placement of rear quarter panel decals for the 1972 model GTO. As the brochures used illustrations that year on many pages, answering this definitely is a bit risky. We can be more certain with the 455 HO model as factory pics were made of that car. It stands to reason that the GTO portion of decal placement remains the same as the bottom line of the decal just changed the lettering and numbers from 455 HO to 455 CID. The reference point needed is just for the GTO part of the decal and we can cover that.
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| 1972 LeMans and GTO specs sheet. |
Shown as well are the spec sheets for the 1971 and 1972 GTO LeMans base 455 engines as well as model availability. Note that Pontiac's new Luxury LeMans trim level wasn't available with the Y code in 1972. In 1971 by contrast, even the lowly T-37 was available with the 455 in base or HO power levels. Of interest to observe are the compression ratios from year to year. In 1971 the base 455 is using ratio. In 1972 the Y code is had 8.2:1 ratio. The 1972 455 HO engine had 8.4:1 ratio, Remember that the HO engine used different heads with round ports compared to the D port head of the Y code.
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The 1971 LeMans GTO chart is shown above. Note the compression ratio is identical to 1972 cars indicating the SAE rating system merely showed what the real installed horsepower was in the car. They didn't lose horsepower, they were rated more
honestly. |
I have also included the 1971 GTO engines chart for comparative purposes. Notice the compression ratios for the engines are the same 1972 models. The SAE rating system was more honest with what you made for power at the rear wheels compared to the flywheel without accessories hooked up.
* Article (c) 2015 by Patrick Smith. Images by PHS MEDIA ARCHIVES.
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