At first glance, you'd think there's nothing to a Y Code frame. What's there to know? Once you start restoring one, a bunch of differences appear. Stuff you didn't realize until you order parts and realize they aren't the same. Or until you buy a replacement frame for your rusted or bent original and discover stuff isn't the same. We're going to walk you through the frame differences and show you.
Let's tackle the 1971 GTO frames first. Since a lot more of them were made than 1972s it stands to reason you might consider using one as a donor. For 1971, Pontiac issued three separate frames for that year. PN 3992389 was the standard frame for engines up to 400 cid displacement. It was open channel, swept hip perimeter design.The only areas boxed were the engine cradle frame horns and the side rails along the rear suspension and axle kick ups.
Frame Part Numbers :
The 455 engine frame used PN 483709 and featured differences in construction from the basic frame. This one used rear frame reinforcement straps leading from the rear axle to the rear suspension bulkhead. The 455 also used a 12 bolt Chevrolet axle assembly instead of a 10 bolt. The engine cradle had special 455 frame to motor mounts installed. Otherwise, it was the same as the standard 400 frame save for the part number and build sheet code. The third frame was PN 483710 and was used for convertible applications and as an optional, HD boxed frame application. It has enclosed side rails instead of open channel and in the case of 455 engine usage it would also have rear frame reinforcement straps and the 12 bolt axle assembly. Reproductions of these parts are readily available by the way.
For 1972, Pontiac used 3 frames again but with different part numbers. The standard frame PN6263668 was used for engines up to and including the 400 CID. It was open channel swept hip perimeter construction. The 455 engine order paired the body to PN 487227 which was open channel as well but supplied 455 motor mounts, 12 bolt axle with rear frame reinforcements. This was what you got with a Y Code hardtop or coupe order. Since the GTO option wasn't available on a convertible this year, the LeMans Sport was the model you needed to order to get PN 487228 which was a HD boxed frame. It was also used when you ordered the HD boxed frame option for your car. It is theoretically possible to find this frame in a Y Code hardtop or coupe. It will be the frame used in a LeMans Sport convertible.
Here is another angle of a 455 engine to frame mount. See how far out they reach past the cradle. Ron Bavis pic credit: |
455 rubber engine to frame brackets are unique as well and must be used if installing the engine using 455 engine to frame brackets. |