Carter Thermoquads ~ 'More General Information'

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69 Cuda 440

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Carter Thermoquads

First found on the 1971 Mopar 340/275 HP Engines.

* 4972S {Manual Transmission}
* 4973S {Automatic Transmission}

* Primary ....... 1 3/8" {1.375"} ........ Venturi = 1.063"
* Secondary ... 2 1/4" {2.250"}

'Originally' advertised at 800 CFM's, but numbers were closer to a 'tad' under 750 CFM's.
at 737 CFM's.

This Carburetor replaced the Carter AVS {630 CFM} that was found on
the 1968 -thru- 1970 340/275 HP Engines.

With the 'new style' Cast Iron Intake Manifold {1 3/8" Primary and 2 1/4" Secondary}
Throttle-Bore openings with the 'Butterfly-design', this combination put out more
Horsepower on the 1971 '340' than the 'earlier' Intake and Carburetor of
the 1968 -thru- 1970 '340'.

The 1971 Thermoquad came thru with ;
* Primary Jets ....... .074"
* Secondary Jets ... .125"
* Metering Rod ....... 655 {.062" Economy ~ .040" Power}

* Needle and Seat ... 0.0935"

Generally, the 1 3/8" Primary Throttle-Bore provided for a 'smoother' and better throttle response on the Bottom-End.

On the CFM Rating >
'Carter Carburetor' stated that the Primary-Throttles delivered flow in the range of 225 CFM's, while the Secondary-Throttles provided +500 CFM's.

Netting {in the range} of a Total of 737 CFM's.

'1971' 340 Intake Manifold ....... #3512100
----------------------------------------------------------------------------------

'Thermoquad'

Comprises of '3' Main Sub-Assemblies

A} Aluminum-base Throttle Assembly
B} Phenolic Resin Main-Body
C} Aluminum Fuel Bowl

This combination, provides for up to 20% {24* to 28*} 'cooler' Fuel Temperature in the 'Fuel Bowl' than a 'conventional' all-Aluminum Cast Carburetor.

Advertised as;
* An 'emission-capable' Carburetor
* Superior 'fuel-economy' with smaller Primary Throttles.
* Excellent 'Top-End' performance from the larger Secondary Throttles.
* Minimal external emission attachments

The 1971 Thermoquards were 'Air-Fuel Metered'.

Also, the Primary-Jets were located in the Upper-Bowl cover, and
were pressed-in with O-Rings.

The Secondary-Jets were located in the Main-Body, as they were
with all Thermoquads.
 
Hipolito,

Yes, there is difference in Horsepower Ratings {as per the NHRA 'Stock Class'}

* 1968 -thru- 1970 > 340/275 HP ........... 290 HP
* 1971 ................. > 340/275 HP ............295 HP

The 1971 Carter Thermoquad is generally regarded as delivering
approximately {5 to 7} Horsepower over the Carter AVS.
 
Hipolito

'The Thermoquad Theory'

The average or typical 'fuel temperature' in an all-cast Aluminum Carburetor
fuel-bowl is 130*.

In the Thermoquad with the 'space-age' Phenolic Resin Main Body, the
'fuel temperature' in the fuel bowl was on average 20% {24* to 28*} cooler.
-------------------------------------------------------------------------------------

~ Theory & Analysis ~

* Air Temperature directly effects power.
* Cool-Air is 'denser', so more air will enter the Engine.

A 7.2% Degree 'lower' change in Fuel Temperature will effect
'increase' Horsepower change by {1%}.

The Carter Thermoquad delivered a {20% lower} fuel temperature
in the fuel bowl.

By theory, that was an increase of {+2.7%} in Horsepower gain,
due to 'cooler and denser' air entering the Engine {Intake Manifold}.

So basically, a 'Mopar 340' with a Thermoquad Carburetor produced
approximately {+8 Horsepower} more than a 'Mopar 340' with a
Carter AVS.

Not including an additional {+100 CFM's}.
 
Whats the verdict on a 9314s ? I have a rebuilt unit, any disadvantages for a performance small block? Was always a AVS, edelbrock guy.I think its from a 80's 318 truck. How much was changed during the smog era?
 
Fratz,

You jumped over me by 10-Years, going all the way up to 1981.

What are you, Pete Townsend with the way you leap.

"Squeeze Box"

#9314

Was off the 1981 '360' Dodge Truck.

Primary ....... 1 3/8" {1.375"} ............. Venturi = 1.063
Secondary .... 2 1/4" {2.250"}

These units came thru with
Primary Jets ......... .095"
Secondary Jets ..... .110"

Metering Rods ........ #2210 ...... .069" {Economy} ~ .045" {Power}

These later units came thru with the 'ESA' {Electronic Spark Advance}.

The rear inlet-tube was re-positioned to the rear-center.

And I believe, the 'adapter' for the rear-base port for the vent-hose was replaced by a Fuel-Bowl vent-port.

Though advertised by 'Carter Industries' at {750 to 800 CFM's},
it was rated at closer to 737 CFM's.

This year Thermoquad had 'oodles' of Emission Adapters and Ports.

Personally,

Not my favorite 'Thermoquad in the Barrel'.

As for placing it on a 'Performance Small-Block'.

The 1981 Thermoquads are the 'most complex' and 'least desireable'
units.

I will say 'NO'.
 
69 Cuda 440 said:
Hipolito

'The Thermoquad Theory'

The average or typical 'fuel temperature' in an all-cast Aluminum Carburetor
fuel-bowl is 130*.

In the Thermoquad with the 'space-age' Phenolic Resin Main Body, the
'fuel temperature' in the fuel bowl was on average 20% {24* to 28*} cooler.
-------------------------------------------------------------------------------------

~ Theory & Analysis ~

* Air Temperature directly effects power.
* Cool-Air is 'denser', so more air will enter the Engine.

A 7.2% Degree 'lower' change in Fuel Temperature will effect
'increase' Horsepower change by {1%}.

The Carter Thermoquad delivered a {20% lower} fuel temperature
in the fuel bowl.

By theory, that was an increase of {+2.7%} in Horsepower gain,
due to 'cooler and denser' air entering the Engine {Intake Manifold}.

So basically, a 'Mopar 340' with a Thermoquad Carburetor produced
approximately {+8 Horsepower} more than a 'Mopar 340' with a
Carter AVS.
Click to expand...

...and that doesn't take into account the extra 100+ cfm that the TQ provides over the AVS!
If I remember correctly, all of the other specs were basically the same.
 
I do to want to muck up the thread by adding two cents but the ever so often asked questions about which TQ to use is broken done into these two general categories.

Small 1.38 primary for 273, 318 & very mild 340 or 360 engines.
Large 1.50 for 340 and up.
The race TQ should be used on a race engine and bigger the better for that carb.

Second is the earlier the better due to less emmisions in the cars carb. Truck TQ's have less smog equipment. Skip the first year TQ due to different metering style of the carb. It is also the same as the 1000 cfm race carb.

We now continue with the info thread at large.
Thank you for your patience.
 
rumblefish360 said:
I do to want to muck up the thread by adding two cents but the ever so often asked questions about which TQ to use is broken done into these two general categories.

Small 1.38 primary for 273, 318 & very mild 340 or 360 engines.
Large 1.50 for 340 and up.
The race TQ should be used on a race engine and bigger the better for that carb.

Second is the earlier the better due to less emmisions in the cars carb. Truck TQ's have less smog equipment. Skip the first year TQ due to different metering style of the carb. It is also the same as the 1000 cfm race carb.

We now continue with the info thread at large.
Thank you for your patience.
Click to expand...

Rumble-Man,

Mucking is allowed by me. All opinions about the Thermoquad have 'validity'.

As for the 1980 and later units,,,,,,,,,,, ECCH !!
 
Thanks bro! The later units can be modified but not by me thanks.
 
Also the t-quad intakes were better that the 70 and earlier. 71 340's were the hottest!
 
EL5DEMON340 said:
Also the t-quad intakes were better that the 70 and earlier. 71 340's were the hottest!
Click to expand...

Correct El Mundo Mr. Elds,

The 1971 Cast Iron Intake had 'no' emission attachments, and was a
smooth casting.

Also, the Heat Cross-Over Passage was the 'smallest' of all of the Thermoquad-style Factory Intakes.

Part #3512100

I have 'one' left. Cleaned, and bagged.

To look at it ..........."It smells like VICTORY"
 
1972 Mopar 340/240 HP Engines

#6138S {Manual Transmission}
#6139S {Automatic Transmission}

Primary ....... 1 3/8" {1.375"} ..........Venturi 1.063"
Secondary ... 2 1/4" {2.250"}

Primary Jets ....... .095"
Secondary Jets ... .137"
Metering-Rod ...... 1940 {.070" Economy ~ .046" Mid ~ .040" Power}

The 1972 Thermoquad's were now using Solid {Liquid} Fuel Metering.

Also, the Primary-Jets were now Screw-In type that screwed into inserts located
in the Main-Body instead of the Upper-Bowl cover as in the 1971 Thermoquads.

All Thermoquads were set with a Needle-and-Seat size of {0.0935"}

Again rated at a 'true' 737 CFM's

The 1972 Thermoquads went to 'richer' Jets.

'1972' 340 Intake Manifold ....... #3512100

* Generally regarded as the 'Best' Intake and Thermoquad combination.
 
1972 Mopar 400/255 HP 'Big-Block' Engines

#6140S {Manual Transmission}
#6090S {Automatic Transmission}

Primary ........ 1 1/2" {1.500"} ......... Venturi 1.186"
Secondary .... 2 1/4" {2.250"}

Primary Jets ...... .095"
Secondary Jets .. .137"
Metering-Rod ..... 1939 {Economy .070" ~ .058" Mid ~ .040" Power}

The 'larger' {1.500" Primary} Thermoquad was advertised 800 to 850 CFM's.
but these units were closer to 787 CFM's.
------------------------------------------------------------------------------------

The #6166S Thermoquad was a 'California-only' Carburetor for the
'new' 400/255 HP 'Big-Block.

The Jets were the same as the {#6140S and #6090S} Carburetors,
but the Metering-Rods were different, as they came through with the
{#1938} units.

Metering-Rod .... 1938 {.071 Economy ~ .051" Mid ~ .040" Power}
 
~ Just what were the accurate CFM Ratings of the Carter Thermoquad ~

'Carter Carburetor Company' {ACF Industries} had a different testing method on determining CFM {Cubic Feet per Minute} than it's competitor 'Holley Industries'.

Advertising is one thing, and actual 'flow' was something else.

Were the CFM numbers 'exaggerated'. Well, of course.

When the '1st' Carter Thermoquad came equipped on the factory delivered 'Mopar 340' in 1971, they were all sorts of CFM numbers tossed around.

Mostly, the number that was stated the most was > 800 CFM's

But that seemed 'high', and then it was 750 to 800 CFM's.

The 1 3/8" {1.375"} Primary x 2 1/4" {2.250"} Secondary Thermoquad #4972S had an 'honest guestimate' of 760 CFM's.

But John Bauman {Fuel Technician} for Chrysler Performance let the proverbial 'Cat-out-of-the-Bag' and stated that the #4972S had a flow of 737 CFM's.

So much so, that he even called the Thermoquad the '737' Big Mouth.
 
Dick Landy

'Dick Landy Industries' put the Thermoquad to the Test, to find out what
the true performance of the Thermoquad was against an equal Carburetor.

They tested a Thermoquad #6138S {off the 1972 'Mopar 340'} against a
Holley Carburetor #4777 {4150 Series}.

Equal Comparison

Holley #4777 {Series 4150} 650 CFM ~ 'Double-Pumper' ~ Mechanical Secondaries

Primary Jets ........ .076"
Secondary Jets .... .084"

Performance Test

What they found during testing on a 'Mopar 340'.

* Equal Performance on the Chassis Dyno
* Equal Performance on the Track {1/4 Mile Test Runs}
 
I had a stock 340 1969 Dart auto, 3.23 gears.
With 80K on it.
It would run 14.80's all day.

Swapped to a 1973 340 intake & T-quad.
Boom, 14.40's.

Cheap way to pick up 4/10's.
 
1973 Mopar 340/240 HP Engines

6318S {Manual Transmission}
6319S {Automatic Transmission}

Primary ......... 1 1/4" {1.250"} ........... Venturi 1.063"
Secondary ..... 2 1/4" {2.250"}

Primary Jets ............. .098"
Secondary Jets ......... .137"
Metering Rod {M/T} ... 1962 {.067" Economy ~ .055" Mid ~ .045" Power}
Metering Rod {A/T} ... 1966 {.067" Economy ~ .052" Mid ~ .045" Power}

'1973' 340 Intake Manifold ........ #3671918

CFM Rating ................ 737 CFM's

The 1973 Thermoquads were now equipped with a 'Port' on the Base-Body,
for a Canister-Purge.

Also, a 'Port' was added to the Main-Body, to provide for a vacuum-venturi
signal for the EGR applications.
 
mikedevore said:
I had a stock 340 1969 Dart auto, 3.23 gears.
With 80K on it.
It would run 14.80's all day.

Swapped to a 1973 340 intake & T-quad.
Boom, 14.40's.

Cheap way to pick up 4/10's.
Click to expand...

Damn,that's a big jump. Makes you think twice,before throwing the stock "smog equipment" away. Great thread,as usual 69Cuda440.
 
Abodybomber said:
Damn,that's a big jump. Makes you think twice,before throwing the stock "smog equipment" away. Great thread,as usual 69Cuda440.
Click to expand...

A-B-B,

That is one hell of a leap over the 'Carter AVS' {630 CFM} Carburetor.

I have seen that swap go 2/10's lower, and some at 0.25 lower.

But 4/10's. Maybe the Carter AVS that was on that 1969 Dart GTS 340 to begin
with was a little 'nidget'.
 
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