Thermo-quad Tips
 

I am attempting to build my own Thermo-quad for 72-73 340. I don't want anything on it I don't need
but, leave or modify everything I do. Is anybody willing to share any tips on successful modifications?
Fuel pressure?
Is the vacuum diaphragm on right rear necessary to regulating air door?
Is converting to Holley jets and removing the metering rods from primary circuit the best?
Is removing the choke S/S legal?
Is a -6 inlet adequate for fuel delivery at say 530 HP?

I've read about 40-50 HP differences in modified Thermo-quads so, there must be some things that work better than others.
Thanks

Re: Thermo-quad Tips
 

You might find some suggestion on this site;

http://racingfuelsystems.myfunforum....490f1b3f04bd47

Re: Thermo-quad Tips
 

I run 74 duster in ss/ja 360cid here in finland,.I have problem all the time with accelerate pump seal ring i have use blue and orange rubber,.When it gets race fuel it goes fat and after that wont work at all,.same times cant get engine runnin before I take the thermoguad at pieces and change the rubber,.here in europe we run unleaded racing vp fuel could this be the problem..thanks

Re: Thermo-quad Tips
 

Contact Jim Wahl, he's very good with these carbs. He's a member here.

Re: Thermo-quad Tips
 

Van Lant

Re: Thermo-quad Tips
 

Anyone have a sorce for thermoquad secondary jets

Re: Thermo-quad Tips
 

Sent you a message
Jim

.

Re: Thermo-quad Tips
 

You can buy the good accelerator pump seals from Ninja Fuel Systems on eBay . Compatible with ethanol laced fuel .

Re: Thermo-quad Tips
 

Holley Jets make it a lot easier to tune because readily available.

No metering rods make it a lot quicker to disassemble and assemble
as they are a pain.

Choke must remain in Carb.

-6 works fine...Big float bowl capacity

Diaphragm not vital but helpful in controlling Air Door.


My opinions.......Your results may vary.

Re: Thermo-quad Tips
 

Do you have holly jets in the secondarys, or only in the primarys

Re: Thermo-quad Tips
 

I appreciate all the tips. I have it together and ready for testing.
I need to make a new tool for adjusting the air door spring.


Jim, I did get your message.

Re: Thermo-quad Tips
 

Primary only....Secondary are very unique tall jets and not readily
exchangeable for anything I an aware.

Re: Thermo-quad Tips
 

You can drill stock secondary but start with 131 or larger as approach angle is different on small size.


I would love to find some more original 149 jets!

Re: Thermo-quad Tips
 

John,
How many .149 jets are you looking for I have some

Re: Thermo-quad Tips
 

Has anyone ever made any jet extensions for the secondary that a standard Holley jet would screw in the end? Might have to get the alcohol jets to get ones that are big enough?

Re: Thermo-quad Tips
 

I had a similar thought about the screw-in jet extensions that somebody makes. I'm sure if the height is critical, they could be cut & re-tapped, if needed.

Re: Thermo-quad Tips
 

They could be made on a screw machine if there was enough demand? I'm guessing not that many people would need them. Could run them on a CNC lathe for lower volumes. I'd have to dig out my TQs to see what threads are on the jets and dimensional data.

Re: Thermo-quad Tips
 

Jet # size can still be found if not re-drill and ream!
120-339 .110
120-340 .113
120-341 .116
120-342 .119
120-343 .122
120-344 .125
120-3113 .113
120-3116 .116
120-3119 .119
120-3122 .122
120-3125 .125
120-3128 .128
120-3131 .131

120-5110 .110
120-5125 .125
120-5131 .131 *
120-5137 .137 *
120-5143 .143 *
120-5149 .149 *

Re: Thermo-quad Tips
 

I make sec. jet adapters to use holley jets been doing this for over twenty years if interested PM me

Re: Thermo-quad Tips
 

PM Sent

Re: Thermo-quad Tips
 

Just out of curiosity, who can do a decent restoration on a stock Thermo-Quad carburetor. I picked up an original 73 340 Duster and the car currently has a Holley carb on it and the original Thermo-Quad was in the trunk for obvious reasons. The car sat for about 15 or so years. I checked the plugs, cap, rotor etc. put fresh gas and a fresh battery in it and the car lit off with little issue. It ran and idled remarkably well with great oil pressure. I would like to get the Thermo-Quad done by someone who knows the tricks to make it work for street use and make it look half way decent to the eye.

Re: Thermo-quad Tips
 

Brad Van Lant or George Thompson are outstanding carb builders!

Really optimizing the jetting/Air Door/Accel. Pump are all the tuning
a street car requires. Try different settings and working to find out what the vehicle likes.

Use Air Bleeds to get best idle quality is something we probably all know to do.

Re: Thermo-quad Tips
 

Go to Moparts.com web site type in Scott Smith in search engine. He does fantastic work and is what you are looking for in a street engine application.

Re: Thermo-quad Tips
 

Hi.last weekend at dyno have problems with thermoquad i have 2 fresh race carbs and both same thing.when secondary opens and dyno puts load against motor it dies test tifferent fuel press and bigger secondary jets nothing different.I but 750 vacuum holley it screams to 7000 rpm no problem at all..any tips.thanks and greetings from finland.

Re: Thermo-quad Tipsk on these
 

Increase Air door Tension.

Work with Air Door Opening amt.

I am assuming carbs are put together correctly and floats
adjusted to specs.

Several books on these carbs still available.

If you supply Carb #.....I can give some jet suggestions
and Air Door starting openings.

Sometimes you get carbs that just do not work worth a *****
no matter what you do with them.

Re: Thermo-quad Tipsk on these
 

9800S?


Thank you!

Re: Thermo-quad Tips
 

.074/.075 primary (Holley) no metering rods

.143 Sec. with .790 Air door
OR
.137 sec with .750 Air Door

(Stock unmodified Air Door specs.)

3 turns on Air Door spring tension

These are conservative but will be good baseline in my opinion.

Do not modify emulsion tubes!

9800 Series are excellent carbs to start with.....a replacement carb
calibrated better than the factory installed stuff.

Re: Thermo-quad Tips
 

Thank you sir! I will swap my .149 secondary jet for one of your recommendations.

Are Thermoquads sensitive to fuel pressure? (I usually run 5.5 psi)

Re: Thermo-quad Tipsk on these
 

My thermoguad number is 6545s and second is vin 6453S thanks

Re: Thermo-quad Tips
 

Is your Duster 340 ( High or Low Comp.) or 360.

They have different size primaries (1 3/8 vs 1 1/2).

I will research these carb # and make sure correct for

vehicle as well.

Re: Thermo-quad Tips
 

If I run stock needles and seats...................7 to 8 psi

If I run .110 needles and seats.....................6 is it!

I was giving just ball park baseline settings to help out........In some circumstances of real excellent air/Sea Level and a carb that a big Air Door Opening (Modifications sometimes required for Air Flow) I can use a .149. Particularly in 1 1/2 "Big" Carb (Not legal on 340). Although a lot of my smartest competitors disagree on this jet size.

The small carbs have a restriction in Secondaries Metering that effect
jet tuning. I have drilled out jet totally maybe .180 or more and it makes
no difference over a 149 or even a 143 in some carbs in A/F...as crazy as it seems. Not the case in the big carbs (1 1/2 Pri.).

Sorry for long winded reply.......Currently in bed a lot with health issues and time on my hands (Possible Congestive Heart Failure).

Re: Thermo-quad Tips
 

hi,.sir 360cid.

Re: Thermo-quad Tips
 

Good starting point..................076 (Holley) or .098 with 035 to 037 Rod tip

Big Carbs................................. .143 and .780 Air door to start

Open Air Door 020 at a time on dyno and see what A/F and HP changes.

I prefer 6453 carb as it came on 360 but not critical.

I worry more on AVS carbs switching as they have tabs on boosters for
different engines and manifold combos for air
flow correction ( I think that is why they are there).

Re: Thermo-quad Tips
 

Thank you.where I can buy big jets and rod tips..Or kit of jets and rods.or du I need to find the adapter and use holley parts..

Re: Thermo-quad Tips
 

Some of the carbs come with .143 jets stock.

You can carefully hand drill the Sec. jets out but the approach angles
vary depending on size....Start with 131 or bigger.

No adapter used .....just a tap in the holley size (Carefully again).

Re: Thermo-quad Tips
 

I have one thermoguad that has been in racing motor,not mine.but that carb has vacuum clock and rod.is enyone using these parts to air door adjusting in action,.

Re: Thermo-quad Tips
 

I will work either way.....I like the vacuum pot myself.