Rumble,
[1] A trick I have been doing for years is to solder [ soft lead/tin solder ] the holes in the sec discharge tubes, closed. I then cut off the bullet tip, at an angle [ like the CS TQ, that is where I got the idea ] just where the bullet shape ends. After soldering, run a drill bit up the tube to ensure a blob of solder is not blocking the tube. I use a 80W electric sol iron with 3/8" tip. I would NOT use a Butane torch, not enough heat control, might melt solder in neighbouring hole you just soldered! I have not done back to back dyno tests, but you can feel an improvement. Did dyno a Pontiac 455 with this mod, 850 6000 series TQ on it, had to change sec jets, A/F was good throughout the rpm range. This car weighed 3900# without driver, & with a factory intake manifold & mild 236/230 @ 050 cam [ yes, less exh duration ], 3.3i axle, T400 ran 11.78 @ 115; this was the first time the driver had drag raced. No tuning or experimenting with carb or ign was done, just driven up to the line & raced....
Pretty sure with some tinkering, there would have been another tenth or two in it. Has since run 11.65/119 mph with the same TQ, but different cam & other changes. When people say to the owner, why don't you run a Holley [ or clone ], he replies: 'Because I want to run faster....'
[2] I remove all the choke & fast idle components; doing this leaves a T shaped hole in the AV. I braze a thin piece of steel over this [ keep the weight down ].
[3] With the dashpot pulled in, I like to see about 0.100" of AV movement, free play, where the back of the AV contacts the stop on the airhorn.
[4] With big[ger] cams, the Idle Down Channel will probably need to be increased; this is extremely hard to reach; it is a brass bush buried in the air horn, behind the two alum plugs at the front of the a/horn. It is about 1.375" in & requires long drill bits. I have found they are between 0.048"- 0.052" from the factory. The IDC controls the A/F delivered to the transfer slots, which is where the low speed gets its fuel AND it provides the fuel for tip in, just off idle. Sometimes enlarging the IFR will cure a surging or tip in problem, other times the IDC should be enlarged. Increase by 0.004" as a starting point. If you have an old carb you can cut up, you can better see where the IDC is.
[5] The TQ is the only 4bbl carb that I know of where the met rods are lifted out of the jets with throttle movement; mechanical enrichment if you like. This very clever feature saves some time when the extra fuel is needed because engine load has increased. It is felt as throttle response. This, plus the more direct route the fuel uses to reach the booster, is why brand H [ & clones ] that use a p/valve with the torturous path the fuel takes to get to the main well, can never have the throttle response of a TQ.
[6] As with any engine that has had a larger cam fitted, more idle air is often reqd, this being provided by drilling holes in the pri t/blades. The TQ, as with the QJ, because of the increased booster sensitivity, can suffer from nozzle drip because this extra air is being drawn through the pri bores, activating the main system. So I do not drill the pri blades, I drill the sec blades which do not have n/drip issues. The engine doesn't care how it gets the extra air, as long as it gets it.
[7] Most factory TQs I have seen come with 0.094" needles/seats. That is a bit small for an engine making some HP, so I enlarge them to 0.110". To compensate for the increased fuel level, I increase the FL setting.
If it has brass floats, I set them to 1 1/8", not the stock 1 1/16".
I often wonder if some TQs got bad raps on high hp engines, simply because the N/s were not big enough to feed the engine....
[8] Have never messed with the orifice size in the AV dashpot, might help some combos. Have not tried removing the DP & increasing tension on the AV spring.
And that is about it. Also good tips in the MP book. The fact that combos needed 0.169" sec jets [ not far off 3/16"!! ] using the factory sized main air bleed tells you these carbs flow a lot of air.
I see TQs on Ebay for $600 or more. Not bad for a carb that has not been made in 35 yrs.....
