THERMOQUAD with air metering.

[Blue Grey Duster]

Hey everybody ! I may need some GURU help here, but all comments are welcome. Some times you guys just crack me up.

I have an early 71 TQ 4972, that a guy gave me, I was going to use it if I can. Mopar used it for one year then Carter redesigned it.

My question is, what is the difference between this carb. and the newer ones when it comes to tuning.

I had one on a Duster with an automatic back in 71 and I liked it. This one is for a manual trans. What's the difference ? Jetting and rods are the same.

It would be great to know what I'm doing when I'm doin it !

 

[rumblefish360]

These are a air metered design vs the solid fuel Metered designed. The manual trans shod have a extra pump shot lever on it. There is a recent video on the TQ posted here. Nice video to help set up the TQ.

IMO, trade it to a person needing it since it is a one year only carb for a similar 73+ carb.

 

[Blue Grey Duster]

Thanks Rumblefish

I figured the metering screws were doing the opposite of what you would normally think, but I didn't know if it effected the secondary air valve or any thing else.
The wimsy is a great video! So glad dmoore gave it to us.
You know I say the guy gave me the carb., but it was his way of paying me for helping him. Little did he know it matched the strip kit I had. A nice surprise for me.

I read an article on modifying the TQ years ago. I did it to the old 71 I had, and it turned the tables on this Chevy guy I use to race. He always got me by one or 1 1/2 cars. But not after the mods.

I haven't seen any real mods info. yet. I wish I still had that article.

 

[64DartGTinAZ]

There's an article on Thermoquads in the April 2013 issue of Mopar Muscle (not sure if it's on the newstands yet...came in the mail yesterday). Not sure it has the detail you're looking for (still reading the article), but might be interesting.

 

[demon sizzler]

The '71 4972 and 4973 340 carbs are base on the Competition Series 4846S/4847S and the 4846SA/4847SA carbs. All of these were air metered vs everything after the '71 oem being solid fuel metered.

The only things on '72-up(final production ending in '84) that are inter-changeable with the CS/'71 carbs is:

floats,
needle/seats/gaskets,
floats,
accelerator pump/spring/pump check valve cover/transfer tube,
accelerator pump nozzles/check valve(under cluster)/gasket,
choke pull-off/linkage,
accelerator pump arm/s-link, linkage through '73 model style,
base gaskets, air cleaner gasket, air cleaner stud,
2ndary lockout linkage, and the idle mix screws/springs and the idle speed screw/spring
and the 10 main body screws, float pins.

The advantages to using the '71 carb or the CS carbs is that there is no x-style o-ring(2 of these)to seal the top to the bowl. And the '71 carbs make close to the same power as the '72 340 carbs did.

Dis-advantages would be the lack of available primary and 2ndary jets and metering rods to tune as needed, either new or used. And the price of a good used and complete re builder is about twice or more the price of a '72 340 carb.

The '71 carbs were 800 cfm's while the 4846 carbs were 850 cfm's and the 4847 carbs were 1,000 cfm's. S model CS carbs had a push-in jet held in place with a special viton grade o-ring and the SA CS models had screw-in jets. All of these carbs used the same metering rod style and share like external parts such as

metering rod piston, pull-off/accelerator pump linkages and 2ndary baffle plate and top bowl gasket.

Th CS carbs were a performance after-market carb and were made from approx 1969-1972. These carbs were very nice performing carbs but lacked the sophistication of the metering systems the 1972-up carbs had.

Pic is a full race build using a '73 850 cfm core which now sports approx 1,020 cfm's. These builds with all the right mods will easily support a 700+ hp big block or a 600+ hp small block.