621 Bell Housing - First Design, Second Design?

[David S.]

Hi Guys,

Please take a look at the pictures below. Both are original 621 Bell Housings. Can you advise which is correct for a 70 LT1? It seems the main difference in the two of them is the GM casting in the all orange bell housing at the 12 o' clock position.








Thanks,
Dave

[David S.]

Re: 621 Bell Housing - First Design, Second Design?

[David L.]

Re: 621 Bell Housing - First Design, Second Design?

Dave,

I have an original 621 bellhousing from a 1970 Chevelle BB and the "GM" casting on the side that I bought for my 1970 Camaro SS350 long term project. The castings on the side are as follows:
a large number "5"
circle with a "5" and 4 dots over a "9", another circle a "9" (the 4 dots and "9" might be April 1969 ???)
casting number "3899621"
casting "GM"

Based on my research the bellhousings with the "GM" casting at the 12 o'clock position are 1972-1973 vintage.

Refer to the two links below.

Dave

http://www.nastyz28.com/forum/showthread.php?t=156392&highlight=3899621+bellhousing

http://www.nastyz28.com/forum/showthread.php?t=261693&highlight=3899621+bellhousing

[David S.]

Re: 621 Bell Housing - First Design, Second Design?

Thanks David. I assumed the one with the GM at 12 o'clock was incorrect for a 70. Thanks for confirming.

Best,
Dave

[David L.]

Re: 621 Bell Housing - First Design, Second Design?

Dave,

My original 1970 Chevelle bellhousing (for my 1970 Camaro SS350 project) has the exact same casting numbers etc. as in the photo. I found the photo below on the web. I'm not sure of the meaning of the number "5" but I believe that the date code might be May (the 4 "dots") 1969 (the "9") but that is just my theory.

Dave