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Old 11-07-2002, 11:40 PM
DEMON SIZZLER DEMON SIZZLER is offline
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Join Date: Jan 2001
Location: STONE MT, GA U.S.A.
Age: 62
Posts: 235
Post ThermoQuads 101: the basics.

What I am going to attempt to convey in this post is:

how to id your T.Q.,
how to dissasemble it,
how to clean it(parts too),
how to reasemble it,
basic tweaking,
how to pick the best carb,
how to quickly id the carb,
what parts are available new.

First , let me begin by saying that the ThermoQuad is not too
complicated to understand, but that depending on what carb you
choose and what application it is intended for is most important.
The following info is very useful in selecting a really good baseline carb and you will benefit greatly if your choice is based on the info given, so lets get started.

When you are ready to choose a buildable or suitable carb, first
turn the carb upside down and read the #'s stamped on the primary butterflies. The #'s will be 3 possibilities:
1)2-310 or 2) 2-315 which will allways indicate an 800 cfm carb,
3)2-314 which will allways indicate an 850 cfm carb.
The large secondary butterflies are allways the same size, 2-1/4".

You have 3 important part #'s that id the carb as well:
1)the top plate casting #,
2)the bowl #,
3)the base plate # which will also id the carb's origional application and is found on the driver rear corner of the base plate(4 digit #); examples are:6322, 9014, 9097, 9207 ect.

ThermoQuads were available in 800, 850 and 1,000 cfm ratings and there are 4 sub groups which are:
1)the first run #4846s and #4847s from about 1969 to late 1971
as the aftermarket Competition Series 850 and 1,000 cfm ratings. These(all)carbs were never oem carbs(same for the 1971-1973 Competition Series carbs**see #2 below). The 69-71 carbs had press-in primary/2ndary jets and are not available new.
2)next is the 1971-1973 Competion Series T.Q.'s #4846sa and #4847sa; 850 and 1,000 cfm's respectively and had screw-in jetting, the same as the 1971 1 year only 340 oem carb and the same style metering rods were used on all C.S. and 71 340 carbs.
3)the 1971 ThermoQuad #4972-4 spd or 4973-auto carbs. These carbs are based on the C.S. series carbs but were 800 cfms. Most of these carbs were replaced with the 1972 carbs.
4)the 1972-1974 carbs are the best all-around carbs because these carbs have the least smog implimentation and can be used on virtually any V-8 engine and will deliver very good power #'s
and exceptional gas mileage.
**The 1974 carb has a different boss and accelerator pump lever arm which remained throughout the production of the carbs and a different actuating lever for the accelerator pump link rod, so if you "mix" 72/73 tops with 74 bases and vice versa, you will have to reshape the pump arm link rod.
The 1975 to early 1978 carbs(except truck 440 carbs from 1974-1977)have smog implimented devices that will not readily make for a good performimg/tuneable carb on a cammed up/hopped up engine, so these carbs will need special attention/mods to the top plate/base plate but then will perform as well as a 1972-1974 carb. The late 1978-1984 carbs will in some cases, require a few more mods than the 1975-early 78 carbs but have even better
idle/off idle circuitry and are therefore more "tuneable" than any other year carbs.
The very last run of the T.Q. was the SuperQuad and it was intended to be an aftermarket replacement for all oem T.Q.'s and was rated @ 800 cfm's. This carb was based on the 1975 carbs and had an integral 12 volt choke system.
***Three noteable acceptions were:
1)the 1974 Ford 460 T.Q.'S; 800 cfm carbs;
2)the 1973-1979 International 345/392 truck T.Q.'S;
3)Austrailan Ford T.Q.'S.

Dissasembly proceedures:
start by removing all external linkages;
1)remove the choke pull-off linkage rod at both ends,
2)remove the ckoke plate/attaching rod/linkage rod that connects to the lever above the 2ndary air door,
3)remove the accelerator pump linkage rod,
4)remove the rear 2ndary lock out rod attached to the tear shaped tang:
a)on 1971/1973 carbs, the tear shaped tang was held on with a screw,
b)on 1974-1984 carbs(SuperQuad too)the tear shaped tang is bradded, so removal of the linkage rod is done by turning the loosened tp plate upside down over the bowl and fliping the tang up and manuvering the rod end out of the tang.
5)remove the cover plates to the outside of the metering rods,
6)remove the metering rod piston stop and pull it up by the outer ends/with the metering rods/spring,
7)remove the 10 screws(*two are down in the choke tower towards the back inside wall),
8)remove the accelerator nozzle cluster, and brass check valve,
9)remove the pump arm/attaching screw,
10)remove the accelerator pump by tapping the exposed end
at the top plate casting with an equal diameter punch or bolt and support the top so the whole pump/spring/cover on the bottom side will come out of the top plate***dont loose the spring!!!
11)carefully speprate the top plate/mid section(bowl) and base plate,
12)keep the bowl in the base plate and remove the primary jets from the bowl(brass jets/2,
13)remove the 2 old o-rings from the deep well area to the outside of the primary bores in the bowl,
remove the float pins/floats from the top plate,
14)remove the needles/seats/gaskets(use a dental pick),
remove the two(long brass)2ndary jets from the underside of the top plate,
15)remove the plastic transfer tube between the accelerator
pump housing and the underside of the accelerator pump cluster from the underside of the top plate,
16)remove the screw/choke pull-off,
17)remove the metering rod step up assembly from front of the base plate ,

To clean everything, I use purple cleaner and or carb cleaner spray and use a soft nylon and steel brush on the top plate and base plate and use only the nylon bristle grush on the bowl to clean it. Use an old GO JO can to put all the small parts in with the cleaner and swish it around to clean up the parts.

Closely inspect the accelerator pump well walls for pitting/scoring
or old dried gas and as long as the pitting is not present, and you do not sand the id of the well, you should be ok with a smooth id.
As allways, make sure that there is no binding with the butterflies/shafts as you open and close them.
If there is any aluminum oxidation on the underside of the top
plate, use The Works toilet cleaner on the underside of the top plate(do not get it in the pump well)and use a brush and let it foam up for about 1.5 to 2 min(chemical reaction with the aluminum will take place and heat up the top){wear gloves}and rince thoroughly with water hose outdoors-this is hydrocholoric acid!!!. This process will remove all oxidation if done properly
and repeat as necessary. Dry the aluminum well or it will oxidize again. Just clean like crazy until you cut all the grease/grime.........
you get out of something what you put into it.

To reassemble the carb, follow a few basic quide lines:
1)reverse all the above and:
a)install the 2ndary jets before you install/set the float levels/install the floats,
b)install the new needle seat gaskets by sliding them over one of the 10 long assembly scews and dropping it into the seat holes in the top plate,
c)drop in the 2 o-rings into the bowl the above method,
d)place the bowl in the base plate to install the primary jets; I allways pour a small amount of transmission fluid into a plastic
Coke cap and lube EVERY screw before it is screwed in place as well as all the jets/metering rod piston.
e)allways tork the 140 assembly screws the following method:
first barely seat each screw going 1-10 and repeat the order 4 times, snuging each screw each of the 4 rotations:


x(8) x(7)

x(4) x(3)


x(1) x(2)

x(5) x(6)


x(9) x(10)

f)screw the center slot in the metering rod top counter-clockwise while you push down lightly(after assembly of the carb)
and the piston will keep dropping down; when it stops dropping
down, turn the adjuster screw slot cockwise and just as the piston starts up, turn the adjuster slot 1 full turn to correctly adjust the tree,
g)with the choke pull-off plunger pushed in, adjust the air door by pushing down on one of the air door dimples; the drop before tension on the air door should be .100" for a cammed up engine and .180" on a mild engine or heavy vehicle(over 3,400 lbs).
This is the very BEST method for "dialing-in" the 2ndary air door.
h)for a mild engine, drill the accelerator pump nozzle ids to .031"
and for a more radical engine, start at about .034".

New parts available are:
1)new bowls for the 1972-up carbs, 800 and 850 cfm's;
2)new primary jets, .090"-.105" ids,
3)new 2ndary jets, .100"-.180" ids,
4)new kits for ALL T.Q.'S,
5)new choke pull-offs for all T.Q.'s,
6)new brass floats for all T.Q.'s,
7)new o-rings,
8)new accelerator pump nozzle check valves,
9)new accelerator pumps,
10)new accelerator pump springs,
11)new metering rod piston springs,
12)new gaskets,
13)new 22 degree taper(the good ones)idle mix screws,
14)new accelerator pump well covers,
15)new choke thermostats,
16)new pump arm screws.

I am constantly "looking" for ways to improve the performance and tuneability of these carbs and want very much to see that these carbs are around for a long time to come. I am in the process of finding/drawing up the blueprints to have jets/metering rods made for all models of the ThermoQuad, so if you have any questions/suggestions-positive only, I'm all ears!.
DAVID.

demonsizzler1@cswebmail.com
geocities.com/thermoquads


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