Hi Bill,

Yes, the Big cars used pretty much the same Vacuum linkage/components as the A body.

Although the Bigs did not use a throttle cable.
Instead they used link arms and couplings.

Thanks, Chris

Right Side.

Where would we be without Vacuum.

Brass fittings, steel pipe, crush clamps are what comes off the front carb throttle plate and provides Vacuum for the Power Brake booster, Automatic transmission module and the Vacuum reserve tank.

After this busy intersection comes a check valve leading down to a cast T fitting clamped in place.
One long hose goes to the Vacuum reserve tank mounted up front of the fender skirt.

The other, shorter hose goes to the thermostatic Vacuum control assy.
The purpose of this unit was to disable secondary throttle activation until the engine reached operating temperature (165 degrees).

Right side secondary arm operation.

End carbs were activated by a Vacuum Control diaphragm.

This “Control” mounted to the two RH rear carb studs and provided the pulling power to open the front and rear Rochester’s.

The two end carbs each had a small throttle return spring that clipped into the base plates to assist with deceleration.

The “Automatic” return springs #7013783 were twice the size of a “Manual Shift” spring #7029689 which (helped) on this Suicide Linkage.

I’ve seen many Original Vacuum Tri-Powers converted over to the Mechanical version and these springs were never changed out, because most are unaware.

Thanks for posting thread. Hey 60sstuff, I'm in SF Bay Area as well, curious if I know you? I have a 64 Black GTO w Tri Power. Was thinking of putting the vacuum secondaries back on my car but almost forgot how much I enjoy the ease of having mechanical, which I installed in 89'. My car was built in Fremont as well, First week of February 64'. Anyways thanks for post a great thread that will help future owners if they decide to go this route, very educational and spot on. Dave

Follow-up on tjs44 above question.

This 1966 GTO sold through Hemmings about 9 months ago and offers a good photo of the air condition vacuum hose coming off the hollow carb mounting stud.
You can still see the end of hose marked with dark blue paint just as the shop manual illustration shows.

The knowledge base here never ceases to amaze me. Great summary - thank you.