The Holley Teapot can be modified to work with the ’57 and up distributor. To make this happen, you will essentially adding another hose connection point to the front of the carb and blocking the original port that originally fed vacuum to the distributor.  In stock form, the ported vacuum signal channel in the carb is routed to the spark advance valve which works in tandem with a venturi produced vacuum in providing a tailored vacuum signal to the Load-O-Matic distributor.  For the later model distributors that require a staged or ported vacuum signal, then what is desired is for that vacuum signal to simply be controlled by the movement of the primary throttle blades and not the spark advance valve. The spark advance valve is that unit that looks like a Holley power valve but is screwed in the passenger side (right side for those of you Down Under) of the carb.

While there are several different ways in which to achieve a ‘true’ staged or ported vacuum signal on these particular carbs, I’ll simply go through the methodology that I consider is the simplest.  First remove the small slotted screw plug on the underside of the carb that seals up the passageway that aligns with the original distributor vacuum port opening.  That particular screw has a long stem on it which we will discuss again later.  Now find the aluminum plug on the front of the carb that is aligned with the hole that exits just above the throttle blades when they are either closed or in the proper idle position.  Looking at the front of the carb, there are three of these plugs approximately 1½”-2” above the base of the carb.  You want to be working on the aluminum plug that’s on the far left of all of them.  I’ve found that simply drilling and tapping the plug for an 8-32 screw with a head allows the plug to be easily pulled out without damaging the existing hole.  Once the plug is removed, you have a ¼” hole in the carb casting staring back at you.  If you peer into the hole, you’ll see the small hole that goes into the throttle and is where the ported vacuum signal originates.

At this point, you’ll want to take a   1¼”–1½” length of ¼” O.D. tube and tap into that new hole until it bottoms out.  This is the tube that will eventually be hooked to a rubber hose that connects to the distributor.  While ¼” O.D. steel brake line works, I’ve found that the aluminum fuel transfer tubes used on the 600 cfm Holleys with the flat bowls also works well for this tube.  By fully inserting the new tube in the now exposed hole in the carb front, both the internal hole above and below the tube will be blocked.  That’s part of the plan.  Now back to that long stem slotted screw plug that was removed earlier.  Cut off the stem so that the screw can be reinstalled back in the bottom of the carb.  With the stem in place, the stem simply hits the new tube.  While the new ¼” O.D. tube that was installed should have effectively blocked off this hole, reinstalling the bottom screw is simply a safety measure to insure there is no direct vacuum signal making its way back to the ported vacuum signal.

Now plug the original port at the front of the carb that originally went to the distributor.  This particular port is interconnected with the secondary diaphragm vacuum supply and if not blocked, the secondaries will be sluggish if they work at all.  While not absolutely necessary, removing the spark advance valve and replacing it with a power valve block off plug will also insure that the vacuum secondaries are getting a full vacuum signal.

Once the carb is reinstalled on the engine, simply hook a hose at the new port on the carb and connect the other end of the hose to the vacuum can or pot at the distributor and you are done.

In regards to using ported vacuum signals for the distributor on a dual quad application, one thought process says that you should not need to use but one carburetor for the vacuum signal if both carbs are working together equally. Use the carb closest to the distributor in that case. If designing the carb linkages so that one of the carbs is a primary carburetor (works in advance of the other), then use the primary carb for the distributor vacuum advance signal. But I’ll add that experimenting with the distributor vacuum signal coming from both carbs may solve the problem of the vacuum signal being cut in half when using two carburetors that are working together. Air velocity within a single carb is reduced by half when two carbs are working in tandem.

Using a distributor vacuum advance chamber that can be disassembled so that the spring rate can be altered would be desirable. This goes back to the vacuum signal being cut in half if the carbs are working equally together. For this, the distributor vacuum advance spring rate would need to be lighter to get the vacuum advance to come in at a quicker rate. If using the vacuum signal from both carbs, then there’s a chance that the stock distributor vacuum chamber would work without any modifications.

Anyone else is free to chime in as there are a multitude of variations to making the above scenario workable.