[John V.]

Terry, according to the MPC Tri-Power Illustration, the 3 way Front Carb Fitting used a 9/16"-20 Plug in the LH outlet when not used.

I should not have relied on memory when I made my first post.

Seems I have forgotten a few important things.

First, the '64 GTO with A/C apparently did use a vac source (I didn't go back to check what the vac was for, possibly a valve underhood). This source was taken off the RH outlet of the Center Carb Tee, same as the big car used for the Heater.

The '64 Center Carb Tee Plug was used in numerous applications at least as far back as '59 and was a 5/16"-24 Plug.

But there was an important change for '65.

The '65 Center Carb Tee was revised. It was not the same as the '63-'64 Center Carb Tee (which in turn was different from earlier Tees). The '65 Tee was p/n 9780984.

I believe the main difference (and perhaps only difference) for the '65 Tee was a change in the RH outlet dimension.

When the RH outlet was unused, the Plug used was p/n 9780983 (note the consecutive sequencing of the Tee & Plug p/ns).

This was a 3/8"-24 Plug.

60sstuff, that Front Carb el in your pix looks to be a Threaded Sleeve Elbow. They are commercially available today but may look different. Not sure if you can find one with the correct male and female sizes.

If it was used by the Factory for Man Trans applications in '65 & '66, I was not aware of it.

Like Dick, I had thought the same Front Carb fitting (special 3 way type, maybe Dick can post a pic) was used on all Front Carbs.

In '64, this was true for sure, since all factory T-Ps used the Vac Secondary linkage.

But for '65, the special 3 way fitting is listed in the MPC for both the Tempest & Pontiac T-P with Auto Trans only (they still used the Vac Secondary linkage).

No Front Carb fitting is listed for the '65-'66 T-P with Man Trans which used the Mech Linkage and had no use for Vac off the RH side of the Front Carb.

Lucky for me, if there is a "controversy" about the correct Front Carb fitting, it doesn't involve the '64!

While nothing is listed in the MPC for the '65/'66 Front Carb fitting with Man Trans, the Threaded Sleeve Elbows are listed in Gr. 8.963 in the MPC (along with Threaded Sleeve Connectors and Nuts). The illustration is pretty close to your picture.

So what is the consensus for the '65 Front Carb Fitting with Man Trans? Simple elbow or same 3 way fitting used with the Vac Secondary linkage?