Bad day at the shop

[Skunkworks Challenger]

Phil, good explanation of how the large carbs worked successfully on the smaller engines.  I knew that at some point of throttle advance that the secondaries would kick in.  I had not considered that it would happen if I was just cruising down I-5.  With traffic around here I'm lucky to get to 60 mph.  I do have the 3.23 gears and my secondaries are the larger 1.5" so hopefully that thursty 440 will make 70-70 on the primaries.  It's something I will have to try and see when I finally get it on the road again. Thanks for the insight, if my fuel economy is bad, you may have supplied the answer.  PK

[Challenger6pak]

What is the number on your carb.  It is on the base plate.

[Skunkworks Challenger]

The number on the base plate is 6453SA.  Good guy and very informed " BULLIT" supplied me with the information on the Carter data.  It is www.carburetor.ca/tech/Carter/tqguide-vaanth.html.  Sorry, I don't know how to "activate" the link and there may be a forward slash between carter and tq. It is a great link and has more information than you can ever use on TQ's.  PK

[Bullitt-]

6453S  T/Q is an 850cfm from a 74-360

The Thermo-Quad was available with two primary throttle bore sizes, 1-3/8"
and 1-1/2".  Flow ratings (CFM) vary depending on the source, but
the TQs with the 1-3/8" bores are listed as 750-800 CFM and those with the
1-1/2" primary throttle bores are rated at 800-850 CFM.  All TQs have the
2-1/4" diameter secondary throttle plates. The primary bore size depended
on application.  In general, all 78 and later 318s and 360s and all 340s had
the smaller bore.  Earlier 360s varied depending on application, most 400s
and all 440s had the large bore.  The 9000 series have the small primary bore
and were rated by Carter at 800 cfm.  Later TQs (ie, Lean Burn and ESA
applications, feedback systems) are quoted with less flow ratings, but
this is due to the control of the carburetion system, not the inherent
flow capability of the basic carburetor.  The internal metering is set for
leaner running conditions for Lean Burn.  Either bore size can be tuned
to run well on most engine combinations.  The smaller bore offers a slight
increase throttle response but less overall flow. The different bore sizing,
ie. speadbore, is an aspect that can lead to increased fuel economy while
delivering similar wide open throttle (WOT) performance to an equivalent
standard bore configuration.  The adjustability of the TQ and the
spreadbore configuration allows the use of a large CFM carburetor on
a small displacement engine.

[Challenger6pak]

I agree that is the 850 for the 74 360 with auto trans.  The 4 speed carb has different stepping on the metering rods.  This carb may be too lean for the 440.  If so you will have to drill the jets since the jet kit is no longer available.  I would put it on as is and see what happens. You can rejet this carb without removing it from the manifold. I was questioning due to the old Carter books I have here.  The 340 came with an 800 CFM carb according to the books.  Also I don't have the difference here.  Carter measured their CFM's at a different water level than Holley did.  I don't remember if an 850 Holley flowed more or less than the 850 Carter. It has been 20 years since I used to race with the Thermoquads. Either way you will be able to make a nice running, driveable 440 with the carb you have.

[Skunkworks Challenger]

Great, and thanks for the information!  It seems to follow then, that if the thermoquad is too lean for the 440 or that my "cruising" speed on the primaries is too slow I can increase the jet size to suit? With jet kits no longer available it imperative to use caution when drilling out the jets since it cannot be reversed? A very interesting topic!
Challenger6pak, that is a great "fleet" of E-body's you have.  My Challenger is an original 383 car but that engine was long gone before I bought it.

[Challenger6pak]

Thanks.  Is your car an N code non R/T Challenger? As far as the Thermoquad it might be good to see if you can find any of them in a junk yard etc.  Depending on the original application the jets or metering rods may be different than what you have.  You can mix and match parts to get the mixture you need. I've had places basically give me Thermoquads that have been wet.  You can still use the brass jets and parts from one that has the alluminum all corroded.

[Bullitt-]

Never had a reason to try this but from what I've read adjusting the metering rod piston height can enrich to some degree & bending the tang on the secondary air door can do the same for WOT.   
         Here's the write up
http://www.thermoquads.com/page204.html

[Skunkworks Challenger]

It's getting better all the time, like Christmas in November!  I'm talking about the good information coming from you guys.  I don't see many TQ's at swap meets cause they are not popular around here.  I will try to pick-up a few for parts (jets etc).  Good information in the link, Thanks!  I opened up my TQ today.  I had never seen the inside of one before and I have to say I'm impressed with the simplisity of the design.  Mine appears to be in great shape, just need cleaning. My metering rods are stamped 2002, which means noting to me but must be the size.  I would like to get a kit especially for the accelerator pump.
Challenger6pak, my car is a JS23NOE.  It has a torqueflite, 3.23 gears, slap-stick, rim-blow, black leather, 6-way adjustable drivers seat and a few more neat options.  One option it has is extremely rare, being code C-14 which is rear seat shoulder belts. 

[brads70]

I'd like to see a picture of the C-14 seat belt set up?

[Skunkworks Challenger]

Brad, go to "Vin, Fendertag and Broadcast Sheet numbers" on this web site.  It's near the bottom of the topic list.  Then look down about 13 posts and see "How rare is this", posted my me.  You will see some pictures and some very good information from Barry Washington or "Alaskan T/A".  If you have any questions after reading the posts just let me know.  PK

[Challenger6pak]

I dug out some of my old strip kits.  Copy this chart.  It will help you mix and match with parts carbs.  The article is wrong about the metering rods.  They do a lot.  There are two designs; 2 step and 3 step.  The 3 step is good for the street. It gives you a setting for idle, crusing, and WOT.  The two step is for racing with an idle and WOT setting. They can make a car flood out at idle or misfire at high speed.  I would say they are important. The part numbers on the left are for your metering rods.  The other numbers fit the tall rear jets and some other parts.  I'll have to look into it and I will see if I can put parts to the numbers.

You car is a nice one.  Lots of expensive options for it's day. Post a few pics.

[brads70]

Brad, go to "Vin, Fendertag and Broadcast Sheet numbers" on this web site.  It's near the bottom of the topic list.  Then look down about 13 posts and see "How rare is this", posted my me.  You will see some pictures and some very good information from Barry Washington or "Alaskan T/A".  If you have any questions after reading the posts just let me know.  PK

Found it! Thanks   I was just thinking that would be a nice option to add as I have 3 kids....but good luck finding those parts being so rare and all!

[Skunkworks Challenger]

On the subject of ThermoQuads, in looking over the chart posted by Challenger6pak showing jet sizes I got to thinking that if I need to drill out the jets for a richer mixture that I would need to drill in steps.  Since the metering rods are stepped I would think that the jets are as well.  It seems I could really mess up things if I enlarged only one step.  It appears that my carb has the 75-2002 needles, measuring .065x.052x.040.  Would I want to just enlarge the .040 area to say, .045 or try to increase each increment by say, .003 or.005.  PK

[Challenger6pak]

The jets are the same diameter all the way through.  I would rebuild the carb first and get it on the car.  Then you will be able to tune from there.