Something you don't see every day

 

Great Pic!!

 

I always wondered why some of these J-398662 castings have that extra tang on the aftmost [1/4" NPT] vacuum fitting.... and some do not. The one dated "28" has the tang, the one dated "58" does not. No telling which was cast first, w/o a year indicator.

I believe that the tang came later, which leads me to speculate that the "58" casting was from day 58 of 1968 and the "28" was from day 28 of 1969.

 

In the number 3 runner, the "28" casting has the two holes siamesed, while the "58" does not, the "58" has a dip, or a crease at that location.

 

Never noticed that before. That is only the mount for the throttle dashpot, so should not be significant.

The tangless one is D1S, the tanged one D2

Aha- I just noticed that this tang has a bit of a rough spot, just like on the floor under the thermostat. Like a sprue riser was broken off there. Perhaps a small sprue was added by means of that tang at the vacuum port boss, to aid in the filling of the mold.

Post #5 here

https://classicoldsmobile.com/forums...55-intake.html

shows a #10 SBO intake [1970] with that extra tang off the aftmost vacuum boss...