Fuel System: Cutting pipe on a "StudeMopar's" Thermo-Quad..

[Noxnabaker]

Since I've had enough troble with Quadra-Jet's & had to change carb & ended up with a Thermo-Quad I've run in to a new problem: the TQ is higher than the QJ... & I already had clearance/hight-problems with the QJ.
So: on top, at the back of the rear big holes there's a thick pipe sticking up, does anyone knows what it's for & if I can cut a piece of?
Here's a pic of such carb, seen from the front/driver side:

[Dan Timberlake]

I think that is the bowl vent.
Its purpose is to keep the bowl pressure equal to ambient air pressure entering the carb to keep the jetting consistent. Local high speed air streams whooshing over it could cause low pressure, which would have the effect of leaning the mixture. (It is also what keeps changes in airfilter restriction from changing the mixture very much, since it provides a pressure reference where the pressure drop due to restriction has already occurred.)

Here is a link to a discussion that includes the common recommendations for an angle cut entry (unlike the one in your picture), and keeping the entry away from the air filter lid.

http://speedtalk.com/forum/viewtopic.php?f=1&t=19427

It will be interesting to see how the phenolic body and critical well o-rings get along with today's gasoline.

1971 Mopar tech manual

http://www.imperialclub.com/Repair/Lit/Master/290/cover.htm

[JoeHall]

If clearance is an issue, and must be solved in order to use that carb, I'd cut it off with about 1/4" remaining, and see what happens. If need be, I'd screw a 90 degree elbow of some sort into the cut off nub.

[sals54]

Why not increase clearance somewhere else?? Use shorter motor mounts. If you're using the extremely tall version of the stock mounts, change over to shorter ones. You can drop the engine 3/4" or so and still maintain a safe distance between the oil pan and steering bell crank. Its even possible to dimple the pan slightly for an added measure. Go to a decent auto parts store and check the catalogs for different size "biscuit" mounts. I found some used on older Volvos. The other thing I like about the Volvo mounts are that they are made of a firmer rubber than the stock Stude style.

[SN-60]

I believe there was a contest going on in the mid seventies to see which carb manufacturer could build the most trouble prone carburetor.....And Carter won with it's THERMO-QUAD!!!!!!

[Alan]

I think Nox there has a 318 in his Stude and does not use the Stude mounts. Would have to go look at one of mine and see what you are talking about.

[nwi-region-rat]

The QJ and the TQ were developed at the same time by different groups at Carter...Early QJ say by carter...the rest by rochester. GM bought the QJ Chrysler and International Harvester used the TQ

[junior]

The QJ and the TQ were developed at the same time by different groups at Carter...Early QJ say by carter...the rest by rochester. GM bought the QJ Chrysler and International Harvester used the TQ

I think that Rochester developed the q-jet, and carter built it under licence....and that Carter was the only producer of the thermo-quad, but it`s been a lot of years since I`ve kept up on the subject. Both carbs seem to get a bad rep, but old super stock racers are able to get some pretty quick times out of their cars without resorting to the typical `double pumper`solution that so many resort to.

[Noxnabaker]

My engine-mounts aint possible to lower more, I already tried to get the engine as low & far back as possible, & yes: it's a 318.
A pal looked at it & said I could make a spacer to put on the underside of the middle-point steering-linkage & THEN it would allow me to lower the engine-mounts.

Old/real Volvo's has a lot of stuff in common with Studebaker, my front wheel brake-cylinders I bought in a Volvo garage, it's the same as late 544/PV.

When it comes to all the GM-lovers (mostly Chevy) & their feeling that everything from Chrysler is crap or difficult or whatever... it just gets me so tired; I've had more Chevy's than I can remember & I like them a lot (also Buick & Cadillac) BUT!!!: I'm not interested one bit in cars later than about -68 & looking at the low-price cars of GM & Chrysler... for example I had a Chevelle & a Satellite from same year & both 4-doors & same engine- & gearbox-setup & the Chevy didn't even come close to the solidness the Plymouth showed & the roadholding... Anyway, I've had quite a few Mopars also & a few Fords, but to slander this or that brand for... yeah, for what?

So for TQ-slanders, check out "thermoquad 4 barrel carburater, (part 1)" on youtube, & maby part 2 also.

& the "O-rings" can be replaced, but as I've understood they're square-cut, not ordinary O-rings.

Anyway, I still wonder... or maby I'll just cut a bit of.

[Mike Van Veghten]

Nox -

To actually answer your question, I'd think 1/4" or 3/8" could be removed with out harm.
As another said, it's there to equalize bowl pressure with outside, ambient pressure. The reason it's so tall, is that that way, under hard acceleration, fuel will not slosh out of the bowl.
You may find you cut it so everything fits...but you get end up with an excess amount of fuel under hard acceleration splashing into the carb., you can always solder a short 90 degree fitting on it, with an inch or so long tube facing foward, with a cap on the end, but cut vent hole on the top.

Many Holley guys did/do this. The Holley tubes are very short, before the days of the internal slosh tube, guys would connect the primary and secondary vent tubes with a piece of rubber hose. This hose would have a hole or two cut into the top/center of the tube for venting.

Even as far back as the carburetors on the 56, 57ish Corvettes...they came this way from the factory..!

Mike

[Noxnabaker]

Thanx Mike, this makes sense, I'll try that 1/4!

[rodnutrandy]

Back when the thermoquads were common, the thought was if they performed good, don't mess with them. Seems if they weren't right, taking them apart and trying to correct them was a failure. Maybe none of us new correct procedures for them.

[SN-60]

My engine-mounts aint possible to lower more, I already tried to get the engine as low & far back as possible, & yes: it's a 318.
A pal looked at it & said I could make a spacer to put on the underside of the middle-point steering-linkage & THEN it would allow me to lower the engine-mounts.

Old/real Volvo's has a lot of stuff in common with Studebaker, my front wheel brake-cylinders I bought in a Volvo garage, it's the same as late 544/PV.

When it comes to all the GM-lovers (mostly Chevy) & their feeling that everything from Chrysler is crap or difficult or whatever... it just gets me so tired; I've had more Chevy's than I can remember & I like them a lot (also Buick & Cadillac) BUT!!!: I'm not interested one bit in cars later than about -68 & looking at the low-price cars of GM & Chrysler... for example I had a Chevelle & a Satellite from same year & both 4-doors & same engine- & gearbox-setup & the Chevy didn't even come close to the solidness the Plymouth showed & the roadholding... Anyway, I've had quite a few Mopars also & a few Fords, but to slander this or that brand for... yeah, for what?

So for TQ-slanders, check out "thermoquad 4 barrel carburater, (part 1)" on youtube, & maby part 2 also.

& the "O-rings" can be replaced, but as I've understood they're square-cut, not ordinary O-rings.

Anyway, I still wonder... or maby I'll just cut a bit of.

You have to love a square "o-ring" !!!!!!

[1962larksedan]

I think that Rochester developed the q-jet, and carter built it under licence....and that Carter was the only producer of the thermo-quad, but it`s been a lot of years since I`ve kept up on the subject. Both carbs seem to get a bad rep, but old super stock racers are able to get some pretty quick times out of their cars without resorting to the typical `double pumper`solution that so many resort to.

I DO remember a few Q-jets built under license by Carter, apparently Rochester ran out of production capacity.

[SN-60]

I DO remember a few Q-jets built under license by Carter, apparently Rochester ran out of production capacity.

I believe the Rochester 'Quadra-Jet' to be an easy to deal with, reliable carb.....Not perfect,........ but good.