[HydroBob]

What model year did Pontiac move to the BOP bellhousing pattern? Did the 64 engine still have the old pattern?

[455dan]

Could be wrong ,?
but i believe the 64 intermediates- lemans, tempest and GTO were 1st and got the new style.

while the 1964 Big car still had the older design.
and their were some weird flywheel and starter mounted to bell housing, flex plate /flywheel interchange concerns 1962-63 and 64 in Big car.
The BOP and Caddy mounting sure made things nice for GM's best engine Brands

[John V.]

The '64 big cars used the same 389 block as the '64 GTO.

The '64 big cars continued to use the Borg-Warner T10 4 spd, the '64 A body used the newer designed Muncie 4 spd. The big car went to the Muncie in '65.

The '64 big cars used different man trans bellhousings because the new for '64 A body took advantage of the block mounted starter.

The big car didn't switch to that until '65, the '64 big car retained the older bellhousing mounted starter arrangement.

However, the '64 A body bellhousing will mount to any '64 389 (or '64 421) block. It was also used for the '64 A body 326 V8, not just the GTO 389.

Since all '64 blocks had provision for a block mounted starter, using a bellhousing that requires the use of such a starter is possible even if the block originally was installed in a '64 big car with a bellhousing mount starter.

I don't really know what is considered a BOP bellhousing pattern. But the '65 (and up) bellhousing will also bolt to the '64 blocks.

The '65 (and up) bellhousings feature the clutch inspection "flap" that the '64 A body bellhousing lacks.

I do not know if the '64 A body or later bellhousings will bolt up to a '63 block but since the '63 blocks had no provision for a block mounted starter, I would think it hardly matters as I don't know how you could adapt a block mounted starter to a '63 or earlier block.

Perhaps somebody has figured out how to do it, I simply am not familiar with pre-'64 blocks.