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Old 01-28-2010, 07:19 PM   #31
Duly
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Default Re: Carter Thermoquad "Spreadbore" Stuff

Sounds good, I like that method. K.I.s.s. (keep it simple stupid)

thank you again,
duly
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Old 01-29-2010, 02:57 PM   #32
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Default Re: Carter Thermoquad "Spreadbore" Stuff

Allright mister mayben. I have held my tongue for over 4 weeks now.
I am referring to the photo in post #19 where the accelerator "s" link is installed backwards.
Was this a test?? If so, what did I win?
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Old 01-29-2010, 03:31 PM   #33
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Default Re: Carter Thermoquad "Spreadbore" Stuff

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Originally Posted by 1975ih200 View Post
allright mister mayben. I have held my tongue for over 4 weeks now.
I am referring to the photo in post #19 where the accelerator "s" link is installed backwards.
Was this a test?? If so, what did I win?
Well you obviously know these carbs well!

But in the case of the pic you refer to, there are actually several things that are not "correct" about other assembly points on that particular tq setup. The "s" link is one of those.

In actuality, the position of that link ends up not being important on a well-used carb that has all the link holes as well as the pivot lever wallowed out. Typical of all the cores I see. That means that all rods, links, etc. I end up fudging to make it work properly, that is why I constantly recommend not going by the "specs" found in the aftermarket kit carb sheets. I make all the necessary bends and tweeks in the various link while the carb is in operation. And that is what we did when these things were new on vehicles in warranty no make the sumbitches perform no matter what the "smog" setup called for! Otherwise, the customer was constantly in the shop complaining about the pos new car/truck they just took delivery of and it's non-drivabilty as compared to their trade-in which was not a smog car/truck.

That particular tq was done for a "second chance" for the owner who has participated in this thread. He'd already been bent over with the first one by two other shops and even though I had fixed it to perform finally after correcting all the butcher, the repair I made to the first fuel bowl did not work successfully as we have already alluded to. And that carb which he paid dearly for, had all connecting rods butchered, including an accel pump lever that was mangled beyond use to try and make it work. When I tried to manipulate it back into the correct shape, it broke.

Positioning the "s" link in some spec'd manner does have a "staging" effect on these carbs when used in lightweight vehicles with an automatic trans, but in the case of the IH stuff it makes no difference in performance/operation at all since these motors/platforms require a much healthier pump shot. If we could source new links, levers, hardware, etc. For these mixers we would go by the book, otherwise we just make 'em work. In fact, I've now started "flattening" the "s" link on the rebuilds I do to negate that so-called two stage effect.

The carb in that pic had all the various linkages, etc. Scruued with for hours while installed on the test motor. Some of the mods I did to that stuff made an improvement, some did not. My purpose was to verify what works since I had the opportunity with this carb and was not pressured to get it shipped. That pic was taken just as soon as it went on the adapter for reference, that is not how it went out the door! Though once I proved to myself that the pump shot was better with the link as you see it in the pic, I did not change it back to "spec".
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Old 01-29-2010, 04:09 PM   #34
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Default Re: Carter Thermoquad "Spreadbore" Stuff

Took the traveler out for a test drive, turned out to be many test drives. The tq is very strong from stop, but there was a bog at wot. Actually the very first test drive it was a complete stall at wot. The advance is set at 6 degrees btdc, idle at 675-700 rpm, I have adjusted the secondary air flap spring tension to very loose to tight, and no change. I moved my accelerator pump to the notch you have it in in post#19, seemed to help but still a bog. I also moved the very small screw in the top of the primary rods all the way in no better and then out little by little, which seemed to help but I didn't want to unscrew the thing and mess something up. So what are your thoughts? And as you know this is my first tq so look think of anything even the very obvious. My terminology for this carb May not be the best, so I apologize in advance.

Thanks,
duly
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Old 01-29-2010, 04:49 PM   #35
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Default Re: Carter Thermoquad "Spreadbore" Stuff

We'll get there!

For your first effort, you have done very well! And once ya go through this tuning process, you will fully understand the functionality at play here!

The small screw that raises and lowers the metering rods has a really long travel and one single turn does not have much effect on position of the taper in the jet.

Once the carb is reassembled, I set that "step up" adjustment to the spec/procedure shown in the cts 2313 service manual (vol. 2) under the heading "metering rod adjustment". In actual running though (especially when used with a non-silenced, free-flowing aftermarket air cleaner), I "raise" that rod adjustment by two additional turns for starters. All this kinda stuff will show up nearly imperceptibly on an exhaust gas analyzer if you are doing this with the motor running, but I don't think you will "feel" anything seat-of-the-pants. So start from scratch with the step-up piston/metering rod initial setting and don't make but one single adjustment /tweek at a time!

Also, having the idle mixture screws set properly has everything to do with tip-in/accel pump performance. Get all that stuff set with it at idle, then home in on the secondary actuation stuff. If you read in the previous post I allkude to actually ending up with the acel pump shot much "faster/sooner/greater than the so-called "specs". The specs are for emissions, but tweeking for a healthy pump shot that is richer than spec is imperative for these pig motors!!! There is the "factory" way and there is the "drivability" way that us mechanics figgrd out in the shop so we could make the customers go away happy!

Do you have that manual? If not, I can post a .pdf of that process. Make certain that in any throttle position, there is no binding of the step-up piston and metering rods whatsoever!

The main thing that affects your description of the problem is the correction operation of the "primary diaphragm choke pulloff" located on the passenger side/rear of the carb. Not only does that item have to hold vacuum when applied and not leak down, it must release the link almost instantly when the vacuum signal drops such as when opening the throttle position to wot. If that part impedes the secondary air valve movement by not "unlocking", the counterbalance spring can't do it's thing! Typically, that choke pulloff gets "hard" internally over time and becomes really stiff, that in turns prevents it from reacting as it should to changes in manifold vacuum.

So test the pulloff with a mityvac. Once it's retracted and you can see that it does not "leak down", then quickly release the vacuum trigger and it should pop to the extended position quickly. You might consider that pulloff to be the "brain" for secondary actuation when called upon.

When running the engine in the shop and winging the throttle, it's impossible to make the secondaries react as they should since all that stuff is controlled to an extent by balancing manifold vacuum with the spring tension on the air valve with the engine pulling fairly hard under load.

The "auxiliary choke pulloff" on the other side (if your carb is equipped with one) doesn't have anything to do with this, it's just "insurance" that the choke butterfly is held open against it's stops once the choke stove is fully heated. That is an emissions thing to prevent a possibility of the choke staying partially closed providing an enrichened mixture at idle where the emissions focus was back in the day!

Lottsa monkee-motion going on in those smogerators huh????
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Old 01-29-2010, 05:09 PM   #36
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Default Re: Carter Thermoquad "Spreadbore" Stuff

Since I have a 1977 my service manual doesn't have the tq, so anything you could give me would be much appreciated, I need to see the IH way to set this up. I have tuned the idle mixture screws, and the max vacuum I was showing was 16 hg. I did use the carb rebuild as a guide for initial set up so maybe that's my problem. When I checked the vacuum pull off it held vacuum, but I will double check. I have learned over the years how unbelievable different these trucks are compared to other makes, I can't even get my Dad to help with this kind of stuff anymore because he has grown up with Chevy and can't comprehend how these old trucks work. I have become much more patient, if this would have happened when I first got the truck I would have thrown the tq out, but I enjoy the challenge now and things like this are expected.

Thanks again,
duly
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Old 01-29-2010, 07:16 PM   #37
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Default Re: Carter Thermoquad "Spreadbore" Stuff

Your are exactly right regarding all the nuances and differences in not only the tq carb but nearly all variations of carburetors used in IH apps. But then, the same holds true for chrysler stuff, Ford stuff, etc.

I git real perturbed when folks start throwing out "they are all the same", "no different than anything else", "just like chevrolet", "same as Ford", etc.

Have you taken the time to count the actual number of thermoquad carb model numbers that were produced???? And there are only two different actual versions (primary/secondary bore diameters). Various technical documents point out over four hundred variations! And the introductory training package that carter produced for the tq in late '71 was for the earliest versions which are significantly different from what we re-engineered just two years later and basically "obsoleted" the earlier units!!!

My research shows at least nineteen variations of the tq spread over production years from mid-1973 through the end of the ihc gasoline engine build-out in 1985. The Scout II applications are only a very small snapshot of the entire tq picture involving ihc motors! And that includes the engines they produced for use in chrysler and GM motorhome chassis.

And by the end of production of the last gen "lean-burn" computer controlled tq mixers, these things far exceeded the ability of the mechanic at that point in time to deal with 'em, they were the ultimate throwaway carb and sold at retail for $450>$700 in 1978 dollars! That would be equivalent to about $1900 today! The carb you are using right now has a "list" price in the 1982 ihc parts price list of $385!!!!!! That is well over $1000 obamabucks!

Here's a few pages from the Scout II manual version of the tq, this one should be near identical to what you are dealing with. I've marked the beginning and end of the pertinent stuff to what we're discussing right now.

I'll be gone all day tomorrow (Saturday) for a leetle presentation regarding torqueflite trannys for our club:

http://www.forums.IHPartsAmerica.com...ter-class.html

So see what ya can do when ya have time and we'll chew it up again early Sunday morning!
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File Type: pdf TQ Air Valve Adjust.PDF (6.64 MB, 663 views)
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Old 01-30-2010, 01:00 PM   #38
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Default Re: Carter Thermoquad "Spreadbore" Stuff

Finally got the truck drivable. I set the metering rods following the IH manual directions. At 15/32 it was very lean, I couldn't hardly accelerate without a backfire. So, I adjusted to make them richer, turning screw clockwise. It slowly improved, now I will start to drive and adjust, slowly turning counter-clockwise to lean it out until it doesn't like it, gotta find the sweet spot. The low end and mid range is very responsive, but the wot sounds like a tailpipe at the boat ramp, under water, but faster. Also set the spring tension following the manual directions and left it there. I did notice that the secondary air flaps do not move when I try to push down on them and the truck is running, I am guessing this is correct since the secondaries are vacuum operated and I need to be accelerating in order to make the move.

Thank you for taking time to help,
duly
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Old 02-03-2010, 05:09 PM   #39
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Default Re: Carter Thermoquad "Spreadbore" Stuff

Mr. Mayben,
do you have any ideas on the problem and how to fix it?

Duly
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Old 02-03-2010, 07:01 PM   #40
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Default Re: Carter Thermoquad "Spreadbore" Stuff

Yes, the secondary linkage is "locked out" until the choke pulloff releases (based upon a drop in manifold vacuum). However...for "testing purposes only"...disconnect and plug the vacuum port that feeds that pulloff.

But, the actual secondary throttle shaft is operated by a mechanical linkage, not by vacuum. But a drop in vacuum allows the choke pulloff to "release" and drop out the secondary shaft interlock...so in that respect you are correct. But the secondaries are not truly "vacuum operated" as you find on the Holley modular carbs with vacuum secondary actuators.

If your choke rod is connected and the choke stove is functioning, then once the engine is warmed, that should pull and hold the choke butterfly fully open.

At that point, whether the pulloff functions properly or not is immaterial, the secondaries will open based upon the mechanical interlock on the throttle linkage and the increased air flow pushing the secondary air valve open. It will do that with the vehicle parked when ya wing the throttle wot and then let it snap shut.

You can then go out and drive it and see if it's better or worse. Take your secondary air valve spring adjuster with you and play around with that counterforce and see if you can find a sweet spot!

That choke pulloff we're disabling is designed to hold the choke valve open as a secondary aid to the force exerted by the choke stove unit, it's like a pair of suspenders for when ya wear a belt also! And...it won't allow the secondaries to operate until the engine is up to temp and the choke is fully held open by engine heat and the pulloff.

Disabling that pulloff is either gonna make a big difference, or no difference! If the performance is much better, then ya know the pullloff is not functioning correctly. Those dam things can be really a pita to deal with, even more so on all the quadrajet variations which work the same way.

If it makes no difference, then we'll try something else. One step at a time so we make sure we cover everything!
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Old 02-05-2010, 11:34 AM   #41
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Default Re: Carter Thermoquad "Spreadbore" Stuff

I tried what you said and it's no better. By the way I unhooked both the rods that connect the vacuum pulloffs to the carb to totally eliminate that. I do have a temporary manual choke I control from inside the cab just so I know for sure what the choke is doing. What do you have your primary rod height set to? I want to know so I can adjust mine the same. When I do go to wot it will bog but if I let off a little the truck seems to get back to normal.


Thanks,
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Old 02-06-2010, 08:23 AM   #42
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Default Re: Carter Thermoquad "Spreadbore" Stuff

Quote:
Originally Posted by duly View Post
I tried what you said and it's no better. By the way I unhooked both the rods that connect the vacuum pulloffs to the carb to totally eliminate that. I do have a temporary manual choke I control from inside the cab just so I know for sure what the choke is doing. What do you have your primary rod height set to? I want to know so I can adjust mine the same. When I do go to wot it will bog but if I let off a little the truck seems to get back to normal.


Thanks,
duly
Ok, so your choke pulloff(s) are disabled, the secondary air valve should function normally once the primary throttle position drops out the interlock and allows secondary operation.

As for the setting for the primary metering rod height, I usually don't have to deviate from the initial setting described in the assembly guide. Now I'd go out and spend time playing with that making two turns at a time. After each adjustment, test drive and determine "better" or "worse" or "no change".

Also, tighten the secondary air valve spring by one turn at a time and test drive that.

We're trying to determine if this is a "tuning" issue or a problem with restricted fuel (or metered air) in a carb circuit.

Your description leads me to think there May be a fuel delivery issue and when the secondaries are open, the engine is leaning out. Make certain the float levels are set correctly, that your fuel pump and fuel tank system are clean and delivering sufficient volume/pressure at high rpm (I've had this exact issue occur on chev motorhomes with a quadrajet which was due to inadequate fuel delivery due to a "weak" fuel pump and three clogged fuel filters!!!!).

When you went through the carb, did you very carefully clean out those tiny calibrated orifices in the air bleed tubes (brass) and also clean /verify all the calibrated orifices where you see "brass" from the top/outside of the fuel bowl cover??? I use a welding tip cleaner very carefully to clean and trace every orifice, carb cleaner will not break down any corrosion that will be inside those tubes.

When you remove the secondary metering jets (the long brass tubes), the air bleeds are inside. I remove those from the carb top for cleaning, but I'd caution ya against doing so and simply clean with 'em installed. Atmospheric pressure must enter the top of that tiny brass tube at the top where that bleed tube is pressed into the carb top....very tedious!

One last thing, this is a shot in the dark...

A typical kit includes at least two, sometimes three pair of "o" rings that seal the secondary jets into that problematic area of the fuel bowl that we have to do the repair with epoxy. You will find they are three different cross-sectional thicknesses. One pair is actually an "x" shape in cross section! Those jets must seal tightly down in that well, otherwise raw fuel is metered around the calibration instead of through the calibration! So pick the pair of seals that allows a tight seal when the bowl cover screws are tightened!
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Old 02-08-2010, 01:29 PM   #43
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Default Re: Carter Thermoquad "Spreadbore" Stuff

What do you set your thermoquad floats to? I have mine set at 29/32 in. My fuel delivery from the tank should be good. I just installed a new 33 gallon tank, and have 3 filters, one right after the tank, one right before the fuel pump and one see through glass filter before the carb. I did inspect and clean every tiny orifice I could find when I did the rebuild, and there was only one set of o-rings in my rebuild kit. I took out the secondary metering jets and cleaned those good.

Thanks for the patience,
duly
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Old 02-08-2010, 05:27 PM   #44
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Default Re: Carter Thermoquad "Spreadbore" Stuff

The nitrophyl (plastic) floats set at 29/32" or thereabouts. The brass floats set at 1-1/6".

Use a pressure gauge to test your fuel pressure at both idle and at say 2500rpm. You are looking for a consistent 5>6psi with a delivery rate of 1 pint in 20 seconds.
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Old 02-09-2010, 01:32 PM   #45
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Default Re: Carter Thermoquad "Spreadbore" Stuff

I took some pics of my set up thinking maybe you see something wrong. What do you think about the kickdown linkage?, it seems to stick sometimes. Haven't checked the fuel pressure yet, but it's on the to do list.

[img][/img]

[img][/img]
These vacuum hoses form left to right are egr, pcv, and vacuum advance.

[img][/img]

[img][/img]

Thanks,
duly
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