Early to late differences in 403 Bell Housings?

[NorCam]

I picked up a spare 403 bell housing a few years ago and someone told me this was an early one because it has something different in the design of it? I just stripped all the paint off as I plan on using it on my Zed, but I'm curious how someone could have known if it was early or late when the old date code was buried in 3 layers of paint.

What's the difference with the castings for the early vs late 403? Please and thanks.

[32KZ]

My april 68 looks the same, check crg, I think this topic was covered.

[John Brown]

As I recall, some bells had the GM lettering in a different position, as in higher up or lower down.

[jdv69z]

I thought I was told that they were not dated?

[NorCam]

They are dated. If I flip that image you can see the underlined 10 which represents the month, and I believe the large dot out of the 5 of them signifies the 4th week? I was told today that the year is represented by the single-digit beside the date code and in this case, it's an 8.

If that is right, then it appears I have an early 69 bell housing cast the 4th week of October of 1968

[ZLP955]

Some have the 'GM' on the sloping upper surface, like yours, some have it on the side near the 403, and I recall seeing one that had it in both locations. Not sure which is early and which is late.

[bbbentley]

My Dec 68 (69 model) 396 Camaro has GM on the side. It is a 621.. I would think that the placement of GM would correlate with the 403? I am pretty sure the early April 69 yellow Camaro has its original 403 bell. I’ll have to look for dates on both and report back.

[jdv69z]

Here's mine. I was told the 8 had to do with the foundry line it was run on, or something like that. I see the circles with marks. Of course I cannot read them because of the orange paint.

[jdv69z]

I blew up my photo, and now I can see the circles better. I definitely see a 3, and several dots in the bottom of the circle.

[rszmjt]

This is a quote from John Hinkley on 403 bellhousing numbers off Camaros.net from 2004 I was involved in-

"The round markers are coded the same way they are on Muncie castings. The large numbers are die-cast mold identifiers."
JohnZ
CRG



FWIW - I have been keeping track of the differences in 403 bellhousings for 20 + years and have found examples where the mold ID numbers range anywhere from 1-9, the difference noted between early and late 403 are as follows -

later issue 403,s (late 69 -72) all seem to have a extra boss on passenger side just above the block dowel hole, but it is not allways just late as some early 403 have this passenger side boss, additionally this boss is also on ALL 403 bellhousings on drivers side location just above dowel also. Sometimes this drivers side boss is tapped to accept the clutch crosshaft ball for 66-72 Corvette and other applications.

Also a lot of the earlier 403 bellhousings (1-6 mold number) have a raised type lip around the pad area where the 403 is cast along with the mold number ( 1-9) and the round month/week date marker. 1-12 for month and 1-5 dots for week.

The GM cast logo is on all bellhousings just above trans and also sometimes it is also on the pad area where the 403 numbers are cast.