Mighty Demon and the SD 625 are Holleys compared to TQ's.
The TQ "rod tree" can be adjusted for a global AF change, not normally tweaked but for high altitude areas.
check this link out Carter Thermoquad Information Page
"...Secondary Circuit Mixture Adjustment
The secondary circuit controls the fuel mixture throught the secondary throats, thus is only used under full throttle conditions. This mixture is controlled by two fixed jets which are screwed into the underside of the top cover. These jets look like two long brass cylinders.
Thus the only adjustment of the secondary mixture possible is replacement of these jets. Seat of the pants tuning is possible here - if it feels faster, the jets are probably closer to correct. Again, a run on a dynomometer will enable a more accurate result.
However, availability of alternative jets is limited: see my notes above regarding primary jets.
Secondary Throats Air-door Adjustment
The Thermoquad's secondary throttles are opened via a mechanical linkage to the primary throttles, beginning to open once the primary throttles are approximately 3/4 open, and becoming fully open at the same time as the primary throttles become fully open. There is also an air-door (similar to a choke butterfly in appearance) mounted at the top of the secondary throats, and clearly visible with the air-cleaner removed. This air-door is held closed via a spring, and will only open when the vacuum beneath it (created by the secondary throttles having opened) is sufficient to overcome the tension in the closing spring. This air-door enables a smooth transition to wide-open throttle in the following manner: because of the spring-loading of this door, it will be sucked open a short time after the secondary throttle plates are open; the secondary discharge tubes (visibly as two long tubes protruding into the upper sections of the secondary throats) are located above the secondary throttle plates, but below the air-door, thus are exposed to full manifold vacuum in the time between the throttle plates opening and the air-door opening: this ensures fuel flow through the secondary jets will be provoked by the vacuum effect just before the air-door opens and air starts to flow through the secondaries. In curcumstances where manifold vacuum is too low to begin drawing fuel through the secondary jets (eg: full throttle at low engine speed), the air-door will not open either, preventing any flow through the secondary throats, and preventing the engine bogging down through over-carburation.
In practice, there are two ways in which the air-door can be out of adjustment. The air-door spring can be under tensioned, allowing the door to open before fuel flow has started in the secondary jets; or it can be over tensioned, preventing the door from opening until sometime after fuel flow has started in the secondary jets. The first situation will result in a period of too-lean mixture, the second will result in a period of too-rich mixture. Both cases will cause a bog or stumble in the engine as the secondaries are opened.
Before attempting to adjust the air-door, ensure it is not jammed in any way. With the engine off, it should be possible to manually push the air-door fully open. It should move smoothly to it's full open position, and spring back to a closed position immediately when released. With the air-door held open, it is also possible to check the secondary throttles are working correctly. With the choke fully disengaged (push the fast idle screw to it's lowest position and hold there if necessary) look into the secondary throats whilst moving the throttle lever through it's full range. The secondary throttle plates should begin to open when the throttle lever is about 3/4 through it's range, and should become fully open once the lever is moved to it's limit. They should close smoothly as the lever is returned to it's base position.
SPRING ADJUSTMENT:
Eric can supply an invaluable tool for adjusting the secondary air-door
The air-door spring is located inside the carburettor, and is wrapped around the air-door shaft. Looking at the left side of the carburettor, the end of the air-door shaft is visible almost flush with the surface of the carb top cover. The shaft appears to ride in a slotted sleeve, and the end of the shaft itself is slotted. Spring tension is adjusted by turning the shaft itself. The slotted sleeve is actually the shaft lock. To adjust the spring tension, the lock is released by rotating it anti-clockwise, spring tension is then increased by rotating the shaft ANTI-clockwise, or decreased by rotating the shaft CLOCKWISE. When the desired tension is achieved, the shaft is locked by tightening the lock in a clockwise direction. Being spring loaded, of course, the shaft will attempt to spin itself fully clockwise whenever the lock is released. It is therefore necessary to hold the shaft in it's current position whenever the lock is released, or in the process of being locked or released. It's easiest to make these adjustments by using a screwdriver on the shaft, and the factory tool (or a copy of it) to release and tighten the lock whilst the screwdriver holds the shaft in place. It's difficult, but not impossible to just use two screwdrivers.
SPRING BASE SETTING:
Because the shaft will invariably slip out of your grip and spin down to the loosest position, a base setting for the spring tension is achieved as follows. Loosen the lock and allow the shaft to spin out (the air door will flop fully open). Wind the shaft in an ANTI-CLOCKWISE position until the air-door GENTLY closes. Wind the shaft an additional 1.5 turns anti-clockwise. Hold it in this position and tighten the lock.
FURTHER SPRING ADJUSTMENT:
It's easiest to adjust the spring from an under-tensioned starting point. If you feel (on the basis of symptoms described above) that the spring is overtensioned, reduce the tension (by winding the shaft CLOCKWISE) until symptoms of under-tension (ie: mixture leaning out) become evident when flooring the accelerator pedal whilst driving. Once it is obvious that the air-door is opening too soon due to spring under-tension, the object of the adjustment process will be to increase spring tension gradually until the symptoms are _just_ removed. This way, the secondaries will begin flowing air at the soonest possible opportunity, but not an instant too soon, thus maximising acceleration.
So: starting from a situation where the air-door spring is clearly under-tensioned, wind the shaft in 1/4 ANTI-clockwise turn increments, test driving the car in-between adjustments. As soon as the acceleration when the accelerator pedal is floored becomes smooth and forceful, without any bogging or hesitation, stop - dont, make any further adjustments.
Note: In practice, it is difficult to make a Thermoquad transition totally smoothly to full-throttle. Due to the extremely large size of the secondary throats relative to the primary throats, opening the secondary throats will always result in a dramatic slowing of air flow through the carburettor, resulting in at least a minor hesitation. Air-door adjustment is thus a matter of trial and error: starting from the base setting described above, first try reducing the tension on the air-door spring, if this makes the hesitation worse, try increasing the tension on the spring. Only add a 1/4 turn to the adjuster each time. Eventually you will find the position which results in the smoothest transition to full-throttle for your case - but it still may not be all that smooth. In my own experience, a fairly light tension on the spring gives the best result, but your case may be different.
Also, as always, it is assumed the carburettor is otherwise in good condition and correctly adjusted. Other factors can mask or worsen a hesitation on transition to full throttle. Eg: A carburettor that is running over rich may be smoother on opening the secondaries as the rich mixture will mask a momentary leaning out as the secondaries open.