Anybody running a Thermoquad with a “bigger” than stock cam?

[69SuperBee451]

Toying with the idea of trying a Thermoquad on the 451 stroker in my 69 Bee. I’m currently running a 1913 AVS2. It’s an actual 10.65 to 1, 284/528 solid cam that pulls 12in/hg at 1000rpm, DP4B intake (would use an adapter). I have a 9103S from a 77 400 HP that has factory .098” primary jets, .143” secondary, and 2211 rods. I removed the unnecessary choke garbage long ago, added a ported vacuum source in the factory location, and added a curb idle screw. Any suggestions or modifications to ensure it runs right on my 451? Will the idle bypass assist ports make the idle-part throttle transition too lean?

 

[Geoff 2]

Great choice! l
Late last year, a 440 that I built was dynoed with 850 TQ & made 605 hp. Street driver, it also gets 19mpg on trips [ Imperial gal, about 17+ for US gal ].
These mods will make a HUGE improvement:
- enlarge the sec high speed air bleed to 0.039-0.040" if not already.
- set air valve spring to 2 turns.
- use the factory setting for the a/valve fully open position as a starting point.
- factory jetting is ok.
- the above 440 idles with 43* of timing. Yes 43*!!!!!!! Your engine will need similar, 35* or more. A LOT of people do not understand idle timing. Use an adj vac adv unit connected to manifold vacuum [ MVA ] to get the reqd idle timing.
- because of the high idle rpm [ big cam ], the carb will probably require bypass air & may need more than what is built in.
- enlarge the idle feed jets to 0.036".
- use the outer hole on the acc pump arm. Never a need for a lot of pump shot with Carter carbs because of the superior design. Using the outer hole reserves some pump shot.
- modify the sec discharge tubes as shown. Use a 80w elec soldering iron to solder the holes shut. You can see I have missed one hole in the right side tube; should be soldered shut. run a drill bit through the tubes in case any solder went insider. This mod makes a HUUUUUUUUUUGE performance increase. There are pics of this mod in the Fuel section & also an A bodies.

 

[gtxrt]

Late last year, a 440 that I built was dynoed with 850 TQ & made 605 hp

how much HP did it make with a Edelbrock, Holley or quick fuel carb ?

 

[WileE]

Great carb choice and superb reply ^ #2. ( A TQ on a Street Dominator years ago was one of the best combos I've ever personally had )

 

[gtxrt]

Great carb choice and superb reply ^ #2. ( A TQ on a Street Dominator years ago was one of the best combos I've ever personally had )

What were your other combos ? was it a street or race car ?

 

[6PKRTSE]

That will be a good chouce for a carb on that engine. I love the old Thermoquad carbs. Most don't understand how they work or know how to tune them so they get a bad rep. I unfortunately broke the black plastic main body on the Thermoquad from my New Yorker trying to get it apart after 50+ years, so it has one of my Edelbrock carbs on it now.

 

[BSB67]

I’m a little surprised that the OP gets only 10” of vacuum @ 1000 rpm with the 284/528 cam in a 450” engine

 

[70rrclone]

Interesting, I have an 850 TQ on the shelf. I will have to give it a try once I get everything back together.

 

[mmissile]

My "small-block" made 737hp. with a TQ.

 

[69SuperBee451]

That will be a good chouce for a carb on that engine. I love the old Thermoquad carbs. Most don't understand how they work or know how to tune them so they get a bad rep. I unfortunately broke the black plastic main body on the Thermoquad from my New Yorker trying to get it apart after 50+ years, so it has one of my Edelbrock carbs on it now.

Yeah I’ve always run Thermoquads on street cars. I have a stash of over 20 of them, including an original 1000cfm CS Thermoquad. The AVS2 runs great, but if I can pick up an extra 50+ CFM and increased part throttle driveability/part throttle atomization with the TQ, I want to give it a shot.

 

[1967coronet]

Another vote for the thermoquad

 

[Geoff 2]

[1] Referring to post #2, the photo I mentioned. I found it, see below. Do this mod & it will make a HUGE improvement in acceleration. You can see I have brazed a small plate in the A/valve where the hole for the choke linkage was [ I always remove the choke bits, not needed ].

[2] In post #2, I said to open the sec high speed bleed to 0.039-0.040". Many TQs are already this size, so nothing needs to be done. If enlarging from 029 to 039, I would NOT use a 039 drill bit with a hand held pin vise, as it will likely break. [ 010 increase is ok with modellers electric drill ]. Instead, with hand held pin vise, enlarge in 3 steps.

[4] If you study the hole pattern of the sec discharge tubes of the TQ, you will find that the number of holes, size of the holes & position of the holes is different each side, & for different carbs from different engines. This tells you TWO things: each carb was calibrated for a particular engine package....& once any change is made on that engine [ cam, intake etc ], that calibration goes out the window.

 

[Geoff 2]

More info. I have an 850 CS TQ & then fitted one of my modified TQs [ above post ] to the same engine....& my TQ was quicker.

I am not surprised the OPs engine only makes 10" of vac at idle. The BBM have a high rod/stroke ratio, & the cam in use has around 248* duration @050.