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everyothertime
06-26-2009, 06:41 PM
Okies... here's the deal, attached is a bunch of pictures of a Carb, that I believe is a 4 Barrel with a restricter Plate attached to it, cause I've tried to move the lil plates under the flap to open it up but they won't budge... does this mean that Iv'e got the wrong carb on there? do I just need a two barrel? or did someone just want to be flashy and restrict the damn carb? I really would like some help on this one guys... I'm still rather an autimotive idiot...
http://i16.photobucket.com/albums/b50/everyothertime/Marine%20Stuff/0626091636.jpg
http://i16.photobucket.com/albums/b50/everyothertime/Marine%20Stuff/0626091637.jpg
http://i16.photobucket.com/albums/b50/everyothertime/Marine%20Stuff/0626091639.jpg
http://i16.photobucket.com/albums/b50/everyothertime/Marine%20Stuff/0626091638a.jpg

everyothertime
06-26-2009, 06:43 PM
as you can see in the big holes there's two silver lil plates, and those plates don't move at all!!! can someone tell me what I'm looking at??? and I think I need a new carb, so what am I looking at getting? or what should I get as a replacement???

Blind Driver
06-26-2009, 07:06 PM
You may have a Thermoquad on a squarebore intake :oops:

With the restricter plate, at least you can run Talladega now :punk:

robrob
06-26-2009, 07:16 PM
So the big boys will pop in here in a minute and give proper answers. I am too a noob but just went through the similar question. The thermo quad is 4 barrel and a spreadbore which mean most of the time the 2 small barrels open and you get better mileage.

I also learned that the TQ is both loved and loathed...best thing next to fuel injection worst thing since smog pumps....what I figured out was the can be finicky and tough to dial in....I dont really know personally.

Locally folks round here tend toward the edelbrock carbs and I followed suit. Went with a 1406 which needs an adapter (from square bore to spread bore) and requires a little adapter for the throttle/linkage hookup (not really sure which)

Any way hope thi helps...now I will get out of the way and let the folks who actually know what they are talking about answer. Good luck

scoutboy74
06-26-2009, 07:37 PM
That's a Thermobog which would have been OE on a late '70's SII. The intake manifold should be a spreadbore to match the carb unless some unknowing PO swapped a squarebore on there. There's no restrictor plate. I think what you're looking at is the secondary throttle plates. It wouldn't hurt anything to remove this carb for a closer inspection. Just make good note of vacuum hose routing, throttle linkage assembly and other assorted items so that you can put it all back the way it was.

1975IH200
06-26-2009, 07:48 PM
The "lil plates" are the throttle plates. They only move when you actuate the throttle pedal / linkage. Your hand is opening the choke plate (primary) and secondary air valve (secondary) which are both spring loaded closed and opened by the vacumn choke pull-off (primary) and air flow (secondary).

The TQ used by IH is a 750-800 CFM unit.

What exactly is the problem you believe that you have? Does your truck start & run?

everyothertime
06-27-2009, 08:18 AM
Ok first a little bit about the Scout,
its a 1979 Scout II traveler (345 engine that needs to be cleaned up a bit) I use it for both offroading and part time driver out in town. I plan to make it more of an offroading vehicle though.
What is going on is the two silver plates in the big holes don't move at all and have never moved since I've owned it, I'm running Rich and wasting a lot of gas, also I'm pushing a lot of carbon out of my exhaust and fuell seems to be leaking from the carb. a guy at auto zone said I'm gonna have to replace my carb (but he's from autozone, and he's probably trying to sell me one).
I looked at it with the choke propped open and revved the engine up to higher RPMs and the plates just don't move at all, I even tapped on them a little bit (with a screwdriver) to see if they would move which they don't. The only holes that are breathing at all are the little ones. I took it to a Mechanic and he said it might have seized or it might just need to be taken apart and cleaned up. However, it still starts up and runs with the two little holes working fine, and only recently have I been having problems. Thats where I'm getting confused. the mech told me that it was a very good Carburetor when it was new, now its a really bad one! :censored:

Doc Stewart
06-27-2009, 09:37 AM
The Thermoquads with the plastic bodies generally are junk although someone on here has fixed one. If that's what you have, get an Edelbrock! If you have the all-metal TQ, get a kit and rebuild it then tune it to match your engine.

Afireinside2285
06-27-2009, 10:08 AM
Do search for themoquad and you will get more info. than you want.
The secondary barrels(big ones) don't open all the time.It's easy to check if you know what your doing.
That should be factory carb for 79 345
Good luck

Mike_Ert
06-27-2009, 10:49 AM
The secondaries won't open until your foot is really into it. On the Thermoquad they are controlled through manual linkages. While looking down on the carb open both choke plates then actuate the throttle to full throttle manually. If you don't see both the primary and the secondary plates open you have a problem.

IHWILD
06-27-2009, 01:30 PM
The secondaries won't open until your foot is really into it. On the Thermoquad they are controlled through manual linkages. While looking down on the carb open both choke plates then actuate the throttle to full throttle manually. If you don't see both the primary and the secondary plates open you have a problem.

I was pretty sure that the secondaries are vacuum operated but also have sort of an interlock with the linkages. Ie they have to be at a certain throttle position before the vacuum can pull them open. There is even an adjustment on the side which you adjust the vacuum point that they come in at.
Rich

Mike_Ert
06-27-2009, 02:14 PM
I was pretty sure that the secondaries are vacuum operated but also have sort of an interlock with the linkages. Ie they have to be at a certain throttle position before the vacuum can pull them open. There is even an adjustment on the side which you adjust the vacuum point that they come in at.
Rich

I may be wrong but I thought the air door/choke plate on the top is vacuum operated, the actual throttle plates are via linkages.

Afireinside2285
06-27-2009, 02:39 PM
The secondaries are basicly vacume operated with mech linkage.

Mike_Ert
06-27-2009, 03:00 PM
The secondaries are basicly vacume operated with mech linkage.

LOL, well what the hell do I know anyhow. I had to many problems with my Thermoquad and swapped on a Quadrajet. :hammer:

IHWILD
06-27-2009, 04:12 PM
LOL, well what the hell do I know anyhow. I had to many problems with my Thermoquad and swapped on a Quadrajet. :hammer:

I'm probably skipping the quadrajet and going right to FI lol

If the poster needs help I'd suggest getting a service manual or I can try to look it up and explain anything he needs though I might need correction or translation lol... As long as it is Stock for his scout it shouldn't be too far off.

Rich

Afireinside2285
06-27-2009, 04:14 PM
It sounds to me like the fuel bowl is leaking on the bottom two plugs.
good luck

everyothertime
06-27-2009, 05:07 PM
I just put in an order for a Owners manual/tech book.

everyothertime
06-27-2009, 05:46 PM
The Thermoquads with the plastic bodies generally are junk although someone on here has fixed one. I've got the plastic one...so I think I'll just get a new carb. any Ideas???

Erik VanRenselaar
06-27-2009, 05:50 PM
I just put an order on a owners manual/tech book. from what I've been able to tell its the bad version of a quadrajet and now I'm in the market for a new one! any suggestions?

What manual did you order?

The carburetor you have is NOT a Quadrajet; one of your photos plainly shows that it is a Carter ThermoQuad carburetor. I am not aware of a *bad* version of a ThermoQuad, but I do know that my friend (Rusty Scout, here on BP) and I rebuilt the stock T-Quad on his '79 Scout II over 15 years ago, and it still works quite well.
If a T-Quad is properly built, it can be a very good performer, that's economical, too.

Erik VanRenselaar
06-27-2009, 05:58 PM
The Thermoquads with the plastic bodies generally are junk although someone on here has fixed one. If that's what you have, get an Edelbrock! If you have the all-metal TQ, get a kit and rebuild it then tune it to match your engine.

I have never heard of, or seen (photo or in-person) a Carter ThermoQuad carburetor with an all-metal body. The phenolic plastic lower body is what makes the *Thermo* in the carb's name. It insulates the fuel in the float bowls from the heat of the engine.

IHWILD
06-27-2009, 06:01 PM
I've got the plastic one...so I think I'll just get a new carb. any Ideas???

The thermoquad is a subject where both sides of the bush will be beaten to death with no clear winner. If you are looking to replace it then you need to run either another spreadbore carb or a 4 barrel squarebore carb but you would need an adapter for that. I'm not sure how recommended it is to run the squarebore but I know it has been done with Holly Truck Avengers and Edelbrock carbs.

You can check out the fuel injection section but if you are new to engine work that might be something to attack later on.

You can check http://www.thermoquads.com/ for information on that carb itself or you can check with venders for a replacement carb such as the quadrajet which is also a spreadbore.

HTH
Rich

everyothertime
06-27-2009, 06:20 PM
What manual did you order?

The carburetor you have is NOT a Quadrajet; one of your photos plainly shows that it is a Carter ThermoQuad carburetor.

I realized after I put it in that I put Quadrajet, instead of ThermoQuad... sorry about the retard moment :oops: and I ordered the 1978-1980 service manual from scoutparts.com. and now I'm looking at other books just in case :stupid:.

IHWILD
06-27-2009, 06:35 PM
I realized after I put it in that I put Quadrajet, instead of ThermoQuad... sorry about the retard moment :oops: and I ordered the 1978-1980 service manual from scoutparts.com. and now I'm looking at other books just in case :stupid:.

Also look into meeting up with some of the SEBA members (check the club forums for their section.) There should be plenty of people around you that can physically check things out for you and teach you different tricks or trouble points.

Good luck
Rich

1975IH200
06-27-2009, 08:17 PM
There is nothing inherently wrong with a Carter Thermo-Quad carb. I have one on my truck, it has been there since January 1975.

The only thing wrong with YOUR carburetor is that YOU don't know anything about carburetors or about Thermo-Quads in particular.

Get a book for your carb.: Written by Dave Emanual titled "How to Rebuild and Modify Carter/Edelbrock Carburetors" ISBN-13 978-1-932494-36-5 or ISBN-10 1-932494-36-7. Read the book, then read it again before you touch your carb. Lots of color photos, exploded diagrams, rebuild and tuning instructions, etc. etc. etc. Thirteen pages in the book that are specific to rebuilding the Thermo-Quad. Remember: Knowledge beats Ignorance every time.

FYI: This book also covers the AFB (Aluminum Four barrell), the AVS (Air Valve Secondary) 4-barrel carb and the earlier WCFB (Will Carter Four Barrel) carb.

Good Luck with your Traveler.
By the way, "Traveler" was the name of General Robert E. Lee's horse.

Rusty Scout
06-27-2009, 09:50 PM
I fell in love with Carters way back when on my first car. It was a 1968 Dodge Charger 383 4bbl with a Carter AVS and an unsilenced air cleaner. It would let out a terrible moan under full throttle.

My thermoquad has only had a few wear items go out on it. The vacumm pull of on the choke and the other vacum pull off. Also the accelerator pump has failed twice since 1992 when I got the 79 scout.

People have been very skeptical about the phenolic body and complained about warpage. That has never been part of my scout experience and yes the Thermoquad lets out a beautiful moan at wide open throttle too.

I don't think the secondaries will open unless the choke is fully open and fully warmed up.

1975IH200
06-27-2009, 10:38 PM
I don't think the secondaries will open unless the choke is fully open and fully warmed up.
Correct. There is a secondary throttle lockout in the carb. linkage that prevents the secondaries from opening while the engine is cold.

My 1st 4 barrel rebuild was on a neighbors early '50's Buick straight eight with a WCFB, back in the '70's.

bdgn01
06-28-2009, 04:50 AM
Get a book for your carb.: Written by Dave Emanual titled "How to Rebuild and Modify Carter/Edelbrock Carburetors" ISBN-13 978-1-932494-36-5 or ISBN-10 1-932494-36-7. Read the book, then read it again before you touch your carb. Lots of color photos, exploded diagrams, rebuild and tuning instructions, etc. etc. etc. Thirteen pages in the book that are specific to rebuilding the Thermo-Quad. Remember: Knowledge beats Ignorance every time.

Thanks for the info; I've been having some minor issues with my inherited Thermoquad (all my previous experience was with a Holley 1920).

Rusty Scout
06-28-2009, 07:16 AM
One feature I think actually works well is:

Altitude Compensator or Alcomp (Alc):
75-81. This is another driveability enhancement. It appeared on most California and Federal high altitude cars. It appears as a small cylinder attaced to the front of the Idle Enrichment system at the front of the bowl cover. A small bellows inside reacts to altitude changes and alters the air flow in the high speed metering circuit. This improves driveability and reduces emissions by maintaining a correct fuel/air mixture. Note: later vehicles may be equipped with a remote Alcomp sensor (fenderwell) to signal the feedback solenoid controller to compensate.

More free reading on the TQ can be found here:

http://www.carburetor.ca/Tech/Carter/tqguide-Vaanth.html

and here:

http://carburetor.ca/pdf_manuals/Carter/1972TQmanual.pdf

both links are here:

http://www.carburetor.ca/carbs/tech/Carter/TQ-index.html

Rusty Scout
06-28-2009, 07:29 AM
After pondering the symptoms again I would do this.

check to see if the choke is fully open when engine is hot or open it fully by hand to try and bypass the secondary lockout and then open throttle fully by hand and you should see those monster secondaries open.

adjust the idle mixture screws with a vacum gauge and a tach. Doc Stewart just did that on my pickup. if this and the previous test do not fix the rich problem then I would consider rebuilding it myself( or find an honest old coot shadetree mechanic to do it.

Bad Gas mileage??? Its a scout remember. mine gets 10-15mpg usually. Are the plugs fouled black with carbon? Is the air cleaner clogged up? Keep us posted and the trouble will pass.

Rusty Scout
06-28-2009, 07:43 AM
This is an online rebuilding guide that I used the last time I rebuilt the tq

http://www.offroadexchange.com/tquad.htm

below is a crucial excerpt from the site

Here is the number one cause for problems with the Thermoquad. It's this little seal at the bottom of the venturi tube pick-up. When this starts to leak it lets fuel go straight down the carb and floods the engine. A lot of people have thrown this carb away thinking it had gone bad when all it needed was a stupid little seal.


Here's a good shot of where this little bugger lives. It can be a bit tricky to get it in right and it has to be in right. Do not move or shake the body after you have the seal in place before you install the airhorn (top of the carb).

1975IH200
06-28-2009, 12:47 PM
That's a Thermobog ......... Scoutboy74, Typically the "bog" is caused by an incorrectly adjusted secondary air valve spring tension. This is adjustable without any disassembly of the carb.


Another Tip: If you take your Scout off-roading, then put in a pair of p/n 1465 "spring loaded off-road needle & seat asemblies".

Rusty Scout is providing good info on this carb.

everyothertime
06-28-2009, 09:17 PM
Thanks for all the good info guys! as of right now the Scout is parked on base, and I'm moving into my new place (scout moves in tomorrow) I do know that the choke flap for the secondaries (big holes) is broken, so that might be why they're not working... hmmm, after doing a little bit of research, I've found that I'm quite impressed with these carbs (spread bore) and I'm going to attempt to rebuild this current one. I'll keep everyone posted!

Afireinside2285
06-28-2009, 09:25 PM
sounds great they are good carbs do some reading and see what you come up with.
good luck

Rusty Scout
06-29-2009, 12:41 AM
Stuff you need to know about the infamous TQ

The "choke flap over the big secondaries" you were referring to I believe is the secondary air valve which moves on its own accord depending on air flow demand and spring pressure.

The TQ secondary throttle plates are controlled by direct mechanical linkage, air flow is controlled by a secondary, spring tension resisted, air valve. The valve is further controlled and damped by the choke pull-off diaphragm.

The choke is the flap over the small primary bores controlled by a thermostatic coil spring on the intake manifold. In your first pics it appears to be open for the most part.

Secondary air valve:
TQ secondary throttle plates are mechanically linked to the primary on the left side. As the plates begin to open, the secondary air valve senses the opening and begins to open to provide air flow which starts fuel flow from the secondary jets. The initial opening and rate is determined by a counteracting tension spring inside the cover. The opening is additionally regulated and dampened by the choke pull-off assembly. The air valve is contoured and the movement provides a variable venturi effect. A secondary fixed baffle is mounted below the air valve. Total air valve movement is limited by a protruding tab. The counteracting spring tension is adjustable via a slot/lock screw on the left side to tune the rate. Carter designed a special tool to facilitate this adjustment. Some of the CS TQs used an adjustment and lock screw arrangement similar to the AVS.

Choke:
OEM TQs use a divorced, manifold mounted choke. Exhaust crossover heat operates the thermostatic spring contained in the choke well. Most 73-84 TQs were electrically assist heated. The electric control is via a small module mounted to the intake or right head. This unit times the assist based on temperature and time and receives power from the ignition run circuit. 9000 series have an integral choke assembly identified by the black, circular plastic thermostat housing. This unit is electrically controlled. CS units have a manual choke. Choke action is accomplished via the choke plate in the top of the primary side.

Vacuum Pull-Off Choke:
A few models may have an additional pull-off mounted on the left rear. This connects to manifold vacuum via a control switch in the vacuum plumbing. It prevents choke operation after engine warm up.

Rusty Scout
06-29-2009, 12:45 AM
More Crucial Considerations from A Carter Thermo-Quad Guide
Author: Gary Lewallen (aka. Vaanth)
http://www.carburetor.ca/Tech/Carter/tqguide-Vaanth.html


****(Take special note of the main jet well repair with JB Weld....This was one repair I did the last time I rebuilt the TQ)****



Other Considerations:
The TQ can possess the same problems as other carburetors. Some of the features of the TQ can create problems specific to its design. Common problems can usually be remedied with standard repair and tuning practices. Some specific considerations are discussed in this section.

Main jet wells:
The primary jets in 772 and later TQs are screwed into a threaded insert in the fuel bowl bottom. This area is connected via a small plastic channel to the internal fuel pickup area. There is one channel for each jet. These channels are attached to the main body with an epoxy adhesive. The epoxy can weaken and begin leaking with age. Correction can be made by reattaching the wells with new epoxy (J-B Weld has been found to work). Remove the wells and the old epoxy. Clean the area and reattach the wells with a small bead of epoxy. Remove any surplus epoxy that may interfere with reassembly.

Bowl warpage:
Due to the phenolic matterial construction, the fuel bowl can warp. The area most prone to warpage is the upper edge corner of the bowl at the rear. Correction can be made by resurfacing the upper surface. A large flat file can be used to resurface for corner warpage or other irregularities. Warpage of the bootom (unlikely) may require replacement due to its configuration.

Bowl breakage:
Severe breakage may reequire replacement of the fuel bowl. Small breaks and cracks may be repaired with a fuel-resistant epoxy. The bottom surface has tabs for gasket location. If these break, repair is not required if the break does not extend into the bowl. Small breaks around the screw holes do not require repair if the break does not extend into other areas.

Idle transfer slot:
If the primary thhrottle plates are opened too far in an attempt to set the idle speed, the idle transfer slot may be exposed to the air flow. This can result in an off-idle hesitiation. Correction can be made by drilling a 1/16"-1/8" hole in the forward half of each primary throttle plate. The holes allow sufficient air flow for speed setting without exposing the idle transfer slot.

Step-up piston spring:
The step-up piiston spring resists vaccuum pull on the piston. In cases where idle vacuum is too low to allow stable holding of the step-up piston, the spring may be trimmed to reduce its force.

Commercial rebuilders:
Carburetors thhat are mass rebuilt by commercial rebuilders have their useful service life shortened or ended. This usually stems from mixing parts, bad service procedures, and cleaning by tumbling or blasting. Tumbling and blasting removes the factory finishes. This leads to accelerated wear and corrosion problems. In the case of the TQ, the factory linkage was cadmium or irridite finished. The throttle shafts were Teflon coated. Tumbling or blasting removes these finishes and will lead to corroded sticking linkages and binding or leaky shafts. The TQ phenolic fuel bowl can be damaged by tumbling or blasting. Jets, rods and internal orifices are further damaged by these processes. Mixed parts without proper analysis can result in a poorly performing or useless unit. A carburetor from a rebuilder of this nature requires careful examination to determine its future usefulness.