Kendog 170
Let the boy go !
I've never used one but seen them used on Air gap.
Square-bore vs. spread-bore?
- Thread starter Bill Crowell
- Start date
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This guy didn’t. At least looks that way on the Vic. (Below)
A spacer can add an added dimension to the dynamics of the system that is often discounted and/or ignored or brushed off. You have the air flow path going wide to narrow with or at what ever thickness the spacer is. Sometimes a spacer is good, sometimes a spacer isn’t. The only style available is an open spacer. Most times it is around 3/4 of an inch. I have seen 4 hole spreadbore to squarebore adapters for the QJ, not the TQ. IDK if the TQ will fit due to the reduced size of the QJ’s secondary butterflies and there spacing.
A spacer can add an added dimension to the dynamics of the system that is often discounted and/or ignored or brushed off. You have the air flow path going wide to narrow with or at what ever thickness the spacer is. Sometimes a spacer is good, sometimes a spacer isn’t. The only style available is an open spacer. Most times it is around 3/4 of an inch. I have seen 4 hole spreadbore to squarebore adapters for the QJ, not the TQ. IDK if the TQ will fit due to the reduced size of the QJ’s secondary butterflies and there spacing.
Is that a TQ on a race car?
Yes, but not my car.
Captainkirk
Old School Mopar Warrior
Rob, while I haven't run the TQ on a HP manifold, I have bolted it up to a G1 Torker and RPM Air Gap using a Mr. Gasket adapter and the throttle plates all open and function. The biggest hurdle to get around is the choke linkage since it runs off a choke well on the stock manifold. Looks like the guy in the pic fixed that issue by ditching the choke altogether.
That is a (IIRC) demonsizzler prepped TQ with the choke horn front and sides removed. A choke is the last thing it needs. So, yep!
The factory choke is only going to work with an available choke well. Very few aftermarket intakes have this ready to work with the carb. No single car planes have a choke well AFAIK.
I have fussed around with a manual pull cable connected to the factory choke. The have NEVER like the way it turns out. It was workable but a PIA to get it smooth and consistent enough for me to know exactly where the choke was. This is more due to an unfinished tinkering. I guess I could work it out if I really wanted to but I did t wanna go down that rabbit hole myself. I end up looking for perfection rather than leave “Good Enough” and let it ride.
There are 2 styles of TQ’s that can be used easy.
The smaller electric choke versions & the 2 race versions.
Of course we all know of the book on Carter carbs and this book cover picture below. The bottom picture is of the big race version of the TQ where you can see on the upper right side of the picture the clamp and system for a manual choke cable.
The factory choke is only going to work with an available choke well. Very few aftermarket intakes have this ready to work with the carb. No single car planes have a choke well AFAIK.
I have fussed around with a manual pull cable connected to the factory choke. The have NEVER like the way it turns out. It was workable but a PIA to get it smooth and consistent enough for me to know exactly where the choke was. This is more due to an unfinished tinkering. I guess I could work it out if I really wanted to but I did t wanna go down that rabbit hole myself. I end up looking for perfection rather than leave “Good Enough” and let it ride.
There are 2 styles of TQ’s that can be used easy.
The smaller electric choke versions & the 2 race versions.
Of course we all know of the book on Carter carbs and this book cover picture below. The bottom picture is of the big race version of the TQ where you can see on the upper right side of the picture the clamp and system for a manual choke cable.
Captainkirk
Old School Mopar Warrior
I tried going down that rabbit hole many, many moons ago. Ended up using a Holley 650 DP with a manual choke.
lemondana
BlackDart
Put your TQ on a Holley Strip Dominator-The Original Air Gap manifold, long before Edelbrock started using it.
lemondana
BlackDart
When using an adapter, make sure you use one that is for the TQ. The QJet adapter doesn't have as much gasket sealing area in the back between the two mounting bolts as the Thermoquad adapter does. Therefore possible vacuum leak. Edelbrock sells both adapters-get the right one!
Take note of post #35, 100% correct.
To be sure of leak free operation on QJ manifolds or adapters, I epoxy [ I use Devcon ] the passages in the TQ base. I drill a few holes for angled stakes to strengthen the Devcon & make sure it is above the passages; then file/sand flat with base.
To be sure of leak free operation on QJ manifolds or adapters, I epoxy [ I use Devcon ] the passages in the TQ base. I drill a few holes for angled stakes to strengthen the Devcon & make sure it is above the passages; then file/sand flat with base.
lemondana
BlackDart
I have found most of my Thermoquad adapters at swapmeets. They are always the oldest ones, the castings seem better and are made of a heavier material it seems.
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Maybe I missed it but I haven't heard anyone explain why they made the "spread bore" type carb. Probably 90% of the newer generation won't know because their cars have all been fuel injected since the late eighties.
"EMISSIONS" " FUEL ECONOMY" The small primary/large secondary carb gave good low end economy because of the lower cfm flow when only the primaries were open. Generally low speeds and light cruising but had a huge boost when the secondaries opened when passing another car etc... The Thermo -quad was Crates most advanced carburator of the time. The Carter design with the float bowls being one piece allowing the top of the carb to be taken off for service without draining or spilling fuel on the engine, like the Holley. The Phenolic main body was an insulator keeping the fuel many degrees cooler that a standard carb. This allowed denser fuel charges and resistance to vapor lock in hot conditions. The vacuum secondary system ( AVS) allowed for the smooth transition from the primaries to the secondaries with out bogging when tuned properly.
Thermo-quads became the performance carb for Chrysler. Look at the performance engines and cfm rating of those carbs. in the seventies.
Holley dominated the aftermarket in carb sales and that is what drives the manufacturers of manifolds when they design them.. $ale$
"EMISSIONS" " FUEL ECONOMY" The small primary/large secondary carb gave good low end economy because of the lower cfm flow when only the primaries were open. Generally low speeds and light cruising but had a huge boost when the secondaries opened when passing another car etc... The Thermo -quad was Crates most advanced carburator of the time. The Carter design with the float bowls being one piece allowing the top of the carb to be taken off for service without draining or spilling fuel on the engine, like the Holley. The Phenolic main body was an insulator keeping the fuel many degrees cooler that a standard carb. This allowed denser fuel charges and resistance to vapor lock in hot conditions. The vacuum secondary system ( AVS) allowed for the smooth transition from the primaries to the secondaries with out bogging when tuned properly.
Thermo-quads became the performance carb for Chrysler. Look at the performance engines and cfm rating of those carbs. in the seventies.
Holley dominated the aftermarket in carb sales and that is what drives the manufacturers of manifolds when they design them.. $ale$
lemondana
BlackDart
I'll add some carb adapter information here. To start off, back in 1976 when I got my 68 GTS 340, I had to rebuild the engine-just a rering, valve job and a Hemi grind cam. When I got the car it had some ancient little Holley carb on it. I found an original Edelbrock Torker, an adapter and a 850 TQ. It ran hard for what it was, considering I didn't know **** about tuning and such. It always had this loud whistle at idle and lower rpms. My friends said they could always hear me coming even a quarter of a mile away. They called me Whistling Dixie. Some years later I picked up another adapter, and noticed that it worked with the TQ a lot better, no more whistle. I have some pictures, If anyone has any questions-fire away.
Well yeah. Post some pictures. You can educate me.
lemondana
BlackDart
I'll show the difference between the TQ and the Q-Jet adapters and some helpful tips for anyone wanting to try or use one.
So basically the TQ adapter is straight across the back?
lemondana
BlackDart
The first picture is the TQ base with a Q Jet adapter. The area to the right won't leak, but the thin line on the left is where it will leak. The second and third picture are the Q Jet adapter on top of the TQ adapter. All of the pictures of the nuts and bolts, and studs are what is needed when you use an adapter on a manifold that only has the 4 carb mounting holes. Picture #6 is the TQ base on the TQ adapter. Picture #10 is the TQ base on the Q Jet adapter. The first set of 4 bolts are 5/16 X 1" socket head bolts with the circumference and the head ground down to fit flush in the adapter. These bolt the adapter to the manifold with just a thin gasket. The studs are 5/16 X 1 3/4" or 2" from Ace Hardware, they are a lot nicer studs that those that are available from Edelbrock, Holley, or any automotive place. When you buy a new adapter you get hardware with it. I've never bought a new one, so I always sourced the hardware from what I could find. You need a thinwall nut to fit inside the pockets on the adapter. Years ago I found that Ford used SAE 5/16 with a 7/16 head, on their carburetor mounting studs from the 60's thru the 70's on their FE motors, probably others. That's the only place I could find them. I'll further explain if needed.
lemondana
BlackDart
Yes: pretty much, the back edge lines up with the bolt holes fairly closely.
I never realized that. I have a few adapters. I'll have to see which ones they are.
lemondana
BlackDart
There was another member on here that was having a hard time getting his 340 right. He was using a Q Jet adapter. I sold him the TQ adapter, and the last I know he had it running like he thought it should. So many people ***** that they hurt performance. Maybe it does, but my 340 Dart didn't care. I would use another one in a heartbeat.
Depends on if the engine will like the extra plenum to start with. Also, the contour of the adapter (wide to narrow) to the contour of the intakes plenum (a square carb pad to how it enters the plenum and then into the runners) can be a crappy thing as well. Lastly, engine combo & drive train w/the cars weight have an effect on how the whole system works because of the above. If the car is heavy and has Hwy gears & it runs OK or boarder line, but the. Runs crappy with the spacer.....
IF your using a spreadbore to a spreadbore, below is what you want.
Another great feature that the TQ has & the QJ hasn't: the secondaries bleed off cct.
You can get a condition where at cruise, the sec blades are just cracked open, but not enough to open the AV. The AV then acts as a choke & you get an extremely rich mixture.
Carter cleverly has a vacuum bleed off cct to the AV dashpot, such that once the sec blades crack open, the vac to the dashpot bleeds off, allowing the AV to open & admit air so that the mixture is not overly rich. If you open the sec blades, you will see a small hole on the passenger side throttle bore that is blocked off with the blades closed; this the bleed-off port & should be checked for dirt etc when re-building.
You can get a condition where at cruise, the sec blades are just cracked open, but not enough to open the AV. The AV then acts as a choke & you get an extremely rich mixture.
Carter cleverly has a vacuum bleed off cct to the AV dashpot, such that once the sec blades crack open, the vac to the dashpot bleeds off, allowing the AV to open & admit air so that the mixture is not overly rich. If you open the sec blades, you will see a small hole on the passenger side throttle bore that is blocked off with the blades closed; this the bleed-off port & should be checked for dirt etc when re-building.
Bewy, thanks for that explanation about the TQ and QJ spacer differences. I had not knowed all dat.
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