View Full Version : Thermo-Quad

03-20-2016, 09:18 PM
I have had a TQ lying forgotten in a box for years. I have never used it and I don't even remember where it came from. I just found it and took it apart to see if it could be usable. It's blasted and re-manufactured and can not have been much used since. The blasting has of course removed the plating on all levers and rods but otherwise it looks pretty good. According to the #9097S on the throttle body it is a 76' 400cid A/T lean burn carb but the air horn does not have the idle enrichment and there is no electrical parts on it. It looks more like a 72'-74' air horn. The throttle body has a vacuum advance port added but I don't know what other modifications there are and how they should have been made.


The bowl cover has casting # 6-2146, the bowl has # 0-2427A, the main jets are # 4098, the metering rods are missing but # 1966 are available and the secondary jets are # 5137.

Is this a seriously re-built carb or just a pile of mixed parts? Can some one identify the bowl cover by the casting #? Where can I get some information about modifications? I'm thinking of having this on a LA 360 or 390 stroker or perhaps even a mild 440.


03-21-2016, 11:53 AM
The tq is phenomenal when it's right. 2 things that are really critical are new well seals and an intact phenolic body. Well seals have to be replaced every time the carb comes apart. The phenolic body can have cracks. If so can't be used. It's very tricky to get the idle passages clean. Can take a few days of soaking in strong carb cleaner. When the carb is assembled, it's crucial to follow assembly and adjustment procedures step by step. Everything depends on everything, so the manufacturer's sequence is essential, including torquing of the body screws. Most of the tuning involves the metering rods and jets. I wouldn't try to change anything there until it's running. If you then want to do some tuning, it will have to come apart again and well seals changed again. The chance of serious flooding from used well seals is huge.

03-22-2016, 11:43 AM
Thanks chirorod. The phenolic body appears to be in great condition and it's the model with threaded in jets. The cover and base are not completely destroyed by blasting and should work ok. My main concern is if these three main parts are not from the original setup will they work together and since there are obviously some modifications made are they made properly? The vacuum advance port added to the throttle body appears to be decent but I would need to find out what else is added or altered if anything. The air passage from the cover through the bowl and throttle plate is not connected to anything else than the manifold vacuum and I haven't seen any picture of a TQ with a similar passage between the bowl went pipes.
I haven't found any detailed descriptions about modifications on the internet. Do you know if the books "Rebuild & Powertune Carter/Edelbrock Carburetors" and "How to Rebuild and Modify Carter/Edelbrock Carburetors" have good information about mods. I remember that Demon Sizzler was the TQ guru here but is he around anymore?

03-23-2016, 09:14 AM
The pipe sticking up is simply a vent. Really no need to worry about it. I think the hole in the throttle body has to do with a vacuum passage and shouldn't be a concern. The pipe coming out the right side is, I believe, of no consequence. It also vents. On some carbs, it goes to the canister. I don't have the answer to your basic concern about whether the three pieces will work together. Generally, a tq doesn't need any modification other than changing jets and/or metering rods. That's pretty much the opinion of Demon Sizzler, who nobody has heard from in a long time. The tq is incredibly well engineered and self-adapts to almost anything. It's a beast at wide open throttle yet doesn't kill your mileage at light throttle. If you look back on this section, you will find a rather complete discussion of the tq by ehostler. A good source for parts is carbsunlimited.com. Most of what you will see in a manual covering afb's and edelbrocks (same thing) doesn't apply to the tq. If you print out ehostler's work, you will have everything you need. Those idle passages do have to be clear. They are a favorite place for the varnish in gas to harden.

03-25-2016, 09:37 PM
The pipe in the center doe's not look like a vent. The passage goes just straight through the carb and connects to the manifold vacuum. It's not connected to anything else and the hole in the throttle body looks suspiciously home made. Some TQ's seem to have the hot idle compensator valve in this area.




Anyway the passage can be easily plugged from the top so it's easy to test if it should be open or not.

The pipe to the right is the valve operated bowl vent connecting to the canister. The two longer vent pipes at the top are also connected to the bowl so I don't see the point of having a canister connected at all.

I have to investigate how the idle passages and bleeds actually work and check that they are as they should be and clean of any dirt.

I have searched through my FSM's from 72 to 78 and what I have found on internet and here but haven't found any clear answers to my concern yet but I'll keep on looking. I don't think those books I mentioned are worth buying. I think it's better to put the $$ on seals and gaskets and getting the missing metering rods instead to see how it works. Not a big loss if it fails. I have to check my store but I think I already have a RB spread bore manifold somewhere that I bought some 10 years ago at a swap meet for 5€ from a guy who wanted to get rid of it three minutes before closing time.

Thanks for the tip on carbsunlimited. Unfortunately they do not have the metering rods. The only place where I found the metering rods is quadrajetparts.com. They are $12.95 a pair but there are only two options available: .067"/.045" tip, (OEM# 75-1966) or .075"/.041" tip, (OEM# 75-2127).

03-26-2016, 06:05 PM
I have a pair of metering rods. Unfortunately, they are packed away. We are moving, thought we would get the house we put an offer on, and thought we could cut moving time down because there are times when there isn't much time to leave the present house. So we took a couple of storage units to streamline things, and then the deal fell apart. So looking again and the carb parts are in one of the storage units. I dont remember which and which stack.
So I guess that doesn't help. I wasn't aware that the center pipe is for the hot idle compensator. I think just plugging it would work.

06-04-2016, 12:47 PM
Demon Sizzler, who nobody has heard from in a long time.

He has retired and sold the biz and it's parts to Scott Harms who does not do performance mods to the TQ.

06-04-2016, 12:55 PM
He has retired and sold the biz and it's parts to Scott Harms who does not do performance mods to the TQ.

Rumblefish, nice to see you post again. It has been a very long time. Welcome back, if only for a short time. Best regards.

06-04-2016, 12:56 PM
Please drop dead. Thank you.

06-06-2016, 09:06 PM
I had forgotten what a gentleman you were...