365 Bellhousing

[Mike T.]

I have 2 bellhousings with the same casting number-3733365. One is dated late 56 and the other is dated late 58. I thought if 2 GM parts had the same casting number they were the same part. Apparently not. The late 58 bellhousing does not have the bolt hole at the top, and it has a different boss where the starter mounts.

Question is: How common is it for parts with the same casting number to be different, and when did the change take place on the 3733365 bellhousing that eliminated the top mounting hole?
Thanks.

[Joe L.]

Re: 365 Bellhousing

I have 2 bellhousings with the same casting number-3733365. One is dated late 56 and the other is dated late 58. I thought if 2 GM parts had the same casting number they were the same part. Apparently not. The late 58 bellhousing does not have the bolt hole at the top, and it has a different boss where the starter mounts.

Question is: How common is it for parts with the same casting number to be different, and when did the change take place on the 3733365 bellhousing that eliminated the top mounting hole?
Thanks.

Mike-------


It's not unusual for 2 or more finished part numbers to be manufactured (machined) from a same-numbered casting. However, in this case it sounds like there are actually different features of castings with the same casting number. That is quite unusual, especially for significant differences as you've described.

However, are you actually talking about differences in the casting or are you talking about differences in the final machining of the casting? For example, I've never seen one of these bellhousings without the uppermost bolt BOSS. However, I have seen a few in which the upper boss was not drilled for a bolt hole.

[Mike T.]

Re: 365 Bellhousing

Joe. The top boss is there, but it's not drilled. The other difference is down where the starter mounts. The early one has a dogleg type curved section for the starter mounting. This is hard to explain but it's shaped like a reversed crescent moon, (or a reversed letter "C"). The late one doesn't have that casting section. On close inspection, it doesn't look like it was broken off. It is machined smooth and looks factory. Maybe it was broken off and someone, a long time ago, spent a lot of time making it look good. Who knows. Thanks.

Mike-------


It's not unusual for 2 or more finished part numbers to be manufactured (machined) from a same-numbered casting. However, in this case it sounds like there are actually different features of castings with the same casting number. That is quite unusual, especially for significant differences as you've described.

However, are you actually talking about differences in the casting or are you talking about differences in the final machining of the casting? For example, I've never seen one of these bellhousings without the uppermost bolt BOSS. However, I have seen a few in which the upper boss was not drilled for a bolt hole.