Quadrajet under the hood.....?

[Erik Socha]

I have been messing around with my new project over the past few weeks. One of the things that I noticed was a manual choke in the cab of the truck. I thought that this was odd since I have a 1974 & 75 Scout II and neither one of those have a manual choke. I removed the air cleaner to get a closer look and this is what I found......

there is a automatic choke box...however, the rod is disconnected.
You can see the choke cable and the very dirty carb.

then I checked the other side of the carb and noticed this...???

some #'s that I located.
1705721.....there are a few more #'s at the end of this but I could not see them.
3386 awp

anyways, since this an IH I would prefer to go with a oem type carb. I believe that IH used a carter thermoquad carb on the bigger IH v8 motors. If this is the case should I go with the thermoquad. Or some other brand.

I know that I would like to get rid of the manual choke and go back to the oem setup, ie.... An automatic choke.....
Any ideas????

 

[Michael Mayben]

Check this sticky for some background and current tech regarding a spreadbore thermoquad as used on "some" IH applications:

http://www.forums.IHPartsAmerica.com/carb-tech/1390-carter-thermoquad-spreadbore-stuff.html

What you have is a rochester quadrajet that some po has swapped on. And..it's gotta manual choke setup scabbed on also.

Quadrajets, like the thermoquads, were emissions carbs designed for use with either a divorced choke or electric choke system.

Just yesterday I delivered a squarebore Holley to a friend to use onna 360 dodge motor inna ramcharger to replace a rotten edelbrock clone in place. What he thought was a simple aluminum spacer, was in actuality a "spreadbore" adapter that had been installed inna previous life in order to use a much less costly edelbrock. He will be able to mount the Holley I provided to him, but only if the correct gasketing is used also, which I provided with the carb.

Changing over to a "proper" thermoquad for your rig can be a costly situation, and you will need to source and install the oem-type divorced choke system if the one shown in your pic is rotted internally.

Rebuilding a quadrajet takes much attention to some design deficiencies, as does dealing with a thermoquad.

The tq carb was used on 345 sii "California emissions" beginning sometime in '77. Also used on "some" 392 in '74>'75 pickalls.

By the way...that quadrajet is a chev app originally based upon the position of the fuel inlet fitting, there were many variations of that carb produced for many GM apps, a few Ford apps, and some chrysler stuff...but never for IH sv motors.

 

[Michael Mayben]

Just for a reference eric, here's a "before" shot looking down on a quadra I just built. This is onna '89 chev p-30 chassis'd fleetwood motorhome running a 454, last of the non-electronic applications.


These carbs used an electric choke which operates exactly like the electric choke system used on Holley/carter/edlebrock carbs, both oem and aftermarket. But in some GM apps, a divorced choke was used similar to the setup on the IH sv motors.

This one looks considerably better now! It was majorly grunged internally after being rebuilt by a local independent garage three years ago to the tune of $650! And it never operated correctly. Problem was that the "plugs" used in the fuel bowl at the point of manufacture allowed fuel leakage into the manifold plenum when running, resulting inna major over-Rich condition all the time. Any competent carb mechanic knows how to deal with that issue, it's very common. And the carb had an additional circuit which had never been serviced/adjusted, that takes a special tool that I was fortunate to still have in my stash from the old days! But the big issue was that the secondaries were "stuck" closed due to the use of e10 fuel (internal corrosion) that had been allowed to sit in the carb between drives. Due to the cost of fuel, the owner of this rig simply no longer used it as it would not climb the pass out of the valley and got about 2mpg!!!!

After servicing it (and building the carb on the onan 4kw apu which was also munged up), the rig is now seeing it's original 8mpg once again so it's "affordable" to use a few times a year now!

 

[Erik Socha]

Mike, thanks for the information. I have been looking around on other sites to see what thermoquads are selling for.........I guess in the end I would like to purchase one. However, I am going to try my luck at a few junkyards first and go from there.

I just got the line setting ticket from binder books. It confirms that the wagonmaster has a 392. With that being said, can I use any "tq" that I pull of an old IH? (as long as it has the divorced choke.....) is there a certain part / carb # that I need to be looking for?

I found this guy here that sells a rebuild kit at a fair price....
carter thermoquad - the carburetor doctor

 

[Michael Mayben]

There is simply no need to buy a carb kit from any source other than yore neighborhood independent auto supply! A tq kit is very common. I'm using/stocking a standard hygrade p/n 657c for those, got three tq's in progress right now and I have no complaints regarding those kits. All the various standard tq kits have now been consolidated into that one number and they have all parts needed for any variation including the very difficult to obtain accel pump transfer tube:

http://www.forums.IHPartsAmerica.com/carb-tech/1390-carter-thermoquad-spreadbore-stuff.html

We'll be adding some content to that thread in the next few days as kurt's tq goes back together.

I will say this...a Holley modular carb is great for a novice to learn on...a tq or a quadrajet will be a nightmare as much experience in carb work will be needed, they are not a "learner's" carb.

The version of a tq that you need will have two types of choke pulloffs used, one on each side. Those are very problematic. We have freshly remanufactured pulloffs now in the ihon inventory, new are simply not available from any source inna reliable manner that we've been able to dig out.

The magic tq you are looking for will carry a number stamped on the passenger side front mounting boss of 6590s. The fifth digit "s" May or May not be stamped in, that doesn't matter. The ihc versions of these carbs also originally had a triangular aluminum number tag that carried the carter id along with the ihc p/n that would be 451872-c91. That is the 49 state carb, the California carb is different. And you want one with a primary throttle plate diameter of 1.5".

This is a pic of a commercial reman tq that kurt bought outright a few years back and actually was close to the correct tq p/n for his Scout II. However, the "reman" job was shit!

He then sent the carb to a well known IH parts vendor (who shall remain nameless but claimed to be a tq specialist) who advised that the carb could be "fixed" (remember this one was a reman already!). A couplea hunderd bucks later, the dam thang still pours liquid fuel out the bottom and has now been somewhat butchered in the process. Numerous incorrect assembly errors, parts installed incorrectly, no functional accel pump, etc. There are four really obvious fuckups in this one pic view alone!

So this one is a "last chance deal". If it don't work out I'll eat it! And I ain't that hungry.

 

[Erik Socha]

great info. Mike,

I am planning on working on the wagonmaster this weekend. Just wondering if the choke stove that is located on the intake will have a part # that I could compare to a couple that I found on-line. The two that I found have the part #'s of (170-1196) & (170-1701)......

Just found a Scout II tq # 9128s......off of a 345....would this work on my 392?

 

[Erik Socha]

I just picked this up today from stu simpson.....a tq w/ part #490561c91. The carb came from a 345 Scout II.
I am hoping to get some time to take a closer look at the carb.