Small Block Spread Bore Carburetor, Recs?

1970FuryConv

Old Man with a Hat
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I purchased the intake below from C-Body Bob.
1971 Model Year 3512100. (Yes, it will go to a machine shop for clean up. No, I do not care that it weighs 47 lbs. My car is heavy anyway and I have no intention of racing it.)
  • I would like to use the choke heater block off and an electric choke
  • I would like to not use an adapter plate, because I don't want to raise the height of the carburetor. (this manifold puts my carb .25 inch higher than current 2BBL mounting height
  • Edelbrock does not seem to produce a new spread bore carb
  • Holley does. Has anyone used an electric choke spread bore Holley that they would recommend?
  • I saw the 1900/1901 Demons. Would like to know if they bolt up without issues and without much increase in height?
  • Your advice and suggestions are appreciated. Thanks, Ben
PXL_20210404_182302643.jpg
 
Thermoquad, call Dave at Woodruff's.
He has mine now, hopefully get it back shortly. Will let you know results. It ran excellent before except on 2-3 shift it would bog sometimes, I never got around to adding a little more tension to air valve spring.
 
If there is a factory stainless steel choke well cup, then use it with the applicable gasket to seal that hole and then don't install the choke thermostat in it.

The Street Demons have gotten good reviews, usually on Chevies. I do like that it's basically a new version of the Carter ThermoQuad carb, but that it will also fit square-bore intakes as well as spreadbores. The Street Demons are less expensive than the Holley 4175s, especially on sale. I just like the look with the phenolic throttle bowl!

By its nature, the TQ carb is taller than a Holley 4175. I have used the Holley 9895 4175 when it was originally an OEM replacement for the QJet on a '79 Corvette L82 application . . . on my '77 Camaro 305, then with a 355 under it later on. It worked well and added 2mpg to my mileage over the '75 350-spec 4160 I put on it initially (both with electric chokes). Holley later made the 9895 into a universal-fit carb, but it'll still need the Chrysler throttle linkage parts, as will any afternarket carb. But it is quite pricey, compared to what it was as an OEM replacement carb.

With either carb, be sure to use the OEM-style thick base gasket rather than the one they send with the carb. It should have either plastic bushings or metal sleeves in the mounting holes do ensure even torque on the hold-down nuts. Also a better heat insulator, too.

Enjoy!
CBODY67
 
HI WILLIS
If there is a factory stainless steel choke well cup, then use it with the applicable gasket to seal that hole and then don't install the choke thermostat in it.
I HAVE THE CUP
The Street Demons have gotten good reviews, usually on Chevies. I do like that it's basically a new version of the Carter ThermoQuad carb, but that it will also fit square-bore intakes as well as spreadbores. The Street Demons are less expensive than the Holley 4175s, especially on sale. I just like the look with the phenolic throttle bowl!
I LIKE THE DEMON 1901 TOO
By its nature, the TQ carb is taller than a Holley 4175. I have used the Holley 9895 4175 when it was originally an OEM replacement for the QJet on a '79 Corvette L82 application . . . on my '77 Camaro 305, then with a 355 under it later on. It worked well and added 2mpg to my mileage over the '75 350-spec 4160 I put on it initially (both with electric chokes). Holley later made the 9895 into a universal-fit carb, but it'll still need the Chrysler throttle linkage parts, as will any afternarket carb. But it is quite pricey, compared to what it was as an OEM replacement carb.
I LIKE THAT THE DEMON DOES NOT HAVE THE SIDE PIPE. I HAD 4175 ON ANOTHER CAR & COULD NOT GET IT TO STOP LEAKING.
s-l500.jpg

With either carb, be sure to use the OEM-style thick base gasket rather than the one they send with the carb. It should have either plastic bushings or metal sleeves in the mounting holes do ensure even torque on the hold-down nuts. Also a better heat insulator, too.
DO YOU HAVE A PART NUMBER/MANUFACTURER FOR THE GASKET? DOES IT ACT AS AN ADAPTER SO THE DEMON WILL WORK WITH FACTORY SPREAD BORE MANIFOLD? THANKS, BEN
Enjoy!
CBODY67
 
Thermoquad, call Dave at Woodruff's.
He has mine now, hopefully get it back shortly. Will let you know results. It ran excellent before except on 2-3 shift it would bog sometimes, I never got around to adding a little more tension to air valve spring.
HI DAVE
  • CAN A THERMOQUAD BE CONVERTED TO ELECTRIC CHOKE? I HAVE TROUBLE WITH THE CHOKE THERMOSTAT OPENING AT THE RATE I WANT.
  • ANY INFO ON DIFFERENCE BETWEEN KICK DOWN LINKAGE AND BRACKET BETWEEN 1973 HOLLY 2210 AND THERMOQUAD?
  • THANKS, BEN
 
HI DAVE
  • CAN A THERMOQUAD BE CONVERTED TO ELECTRIC CHOKE? I HAVE TROUBLE WITH THE CHOKE THERMOSTAT OPENING AT THE RATE I WANT.
  • ANY INFO ON DIFFERENCE BETWEEN KICK DOWN LINKAGE AND BRACKET BETWEEN 1973 HOLLY 2210 AND THERMOQUAD?
  • THANKS, BEN
The TQ9801 (aftermarket version) came with an elec choke. I bought one and still have it.

Holley only shows the spreadbore thick base gasket. Edelbrock has several square-bore gaskets (attached). The one with the divider is what was on my 1970 Monaco 383 N when I got it. There are also some Chevy Truck Holley 4bbl thick base gaskets with 4 equal holes in them, too. Might need to get into the Edelbrock online catalog to see what the differences are between the 9265 and 12410. Not sure why the only one they currently show in stock is the 12410? Top = 9266 #2 = 9265 Bottom = 12410

I suspect the base gasket for the Street Demon, considering its secondary throttle plate, might be similar to the old Holley 3bbl base gasket?

CBODY67

CAR__EDELBROCK 9266_CARB BASE GSKT_1970 383 N OEM_009266_v1_1.jpg


CAR__EDELBROCK_9265_BASE GSKT KIT_009265_v1_1.jpg


CAR__EDELBROCK_12410_CARB BASE GSKT_012410_v1_1.jpg
 
IF you are near a NAPA store, you might swing by and look in their carb base gasket listings by application or an illustrated listing. Key thing is that they are the thick, OEM-style gaskets (as pictured, but probably without the carb studs and nuts) and not the "thin and soft" gaskets! Personally, I like the "black" hardened studs and then use the normal nuts rather than using the softer steel studs, which have been known to twist off.

CBODY67
 
Holley equivalents. Holley sells some under the "Quick Fuel Technologies" that appear to be the same as their normal Holley items.

Top = 108-12 #2 = 108-18 #3 = 108-25 #4 = 8-812 QFT

CAR__HOLLEY_108-12.jpg


CAR__HOLLEY_108-18.jpg


CAR__HOLLEY_108-25.jpg


CAR__HOLLEY_8-812qft.jpg
 
I've never seen one that will work on a stock lever TQ.
I was going to hook up a manual choke, but you have to make a bracket and a pivot to change direction of the action.
I'm assuming your blocking the heat crossover? Otherwise just use the divorced choke, bend the rod to have it barely close, it should come off quick enough.
If that is not good you could make a bracket to hold a 73 up choke that has a heating element in it it was to have the choke warm faster.
Like this unit
Screenshot_20210406-194405.png

Of course it's out of stock.

They have one for a Lil red with a

Screenshot_20210406-194721.png

Dammit it does not have the heater.
They have other ones but you have to modify.
 
Hi Dave
I've never seen one that will work on a stock lever TQ.
GREAT INFO
I was going to hook up a manual choke, but you have to make a bracket and a pivot to change direction of the action.
I'VE HAD THAT PROBLEM WITH OTHER CARBS. DOABLE, BUT PITA
I'm assuming your blocking the heat crossover? Otherwise just use the divorced choke, bend the rod to have it barely close, it should come off quick enough.
I WAS GOING TO USE A CHOKE BLOCK OFF. IT'S A 71 INTAKE.
If that is not good you could make a bracket to hold a 73 up choke that has a heating element in it it was to have the choke warm faster.
I BELIEVE THE 71 HEATING ELEMENT IS DIFFERENT, SHORTER FRONT TO BACK, BUT I APPRECIATE THAT THE PRINCIPLE IS THE SAME. MAYBE THE BRACKET AND SOME BENDING WOULD WORK. EITHER THAT OR I NEED TO BUY A 71 HEATING ELEMENT.
Like this unit
Of course it's out of stock.
Dammit it does not have the heater.
They have other ones but you have to modify.
EVERYTHING IS OUT OF STOCK WITH PEOPLE STUCK HOME FROM COVID. IT SUCKS! BEN
 
Hello, I have had good success with the Holley street demon carb it is a copy of the old Thermoquad with some sliming down and universal mods.
I really like/love Thermoquads, but you really need to know what could and or is wrong and how to fix it, and have the parts to do it. I have installed this Holley on a couple of cars with the electric choke and they are very happy. I went with the black main body for that Thermoquad look.
Demon 1900 625 CFM Street Demon Carburetor
 
Speaking from personal experience, go Thermoquad.
The least understood carb yet the best for a big heavy car.
Woodruff's will set you up.
When tuned properly, they do perform very well and are reliable.
I use the factory well choke and have no problems regardless the temperature outside.
Remember that the secondaries work in conjunction with the choke--somehow. Lol!
Great fuel economy when cruising and enough balls to overtake any slow tractir trailer on the interstate!
cell sept 2019 225.jpg
 
+1 on the Thermoquad.

The old one that was on my Imperial was trash so I replaced it with a remanufactured unit from Autoline through rockauto. It came adjusted so for me it was just plug 'n play and it ran beautfully. A lot of info online about how to make adjustments as well. The sound of those secondaries opening, love it.

upload_2021-4-13_13-54-48.png
 
Ben,
I'm picking my TQ up from Dave today @ Woodruff's.
I'll have it on in next day or 2 and let you know. I'm sure it will work excellent. I'm not running any choke, just another theft deterrent.
 
Last edited:
Ben,
I'm picking my TQ up from Dave today @ Woodruff's.
I'll have it on in next day or 2 and let you know. I'm sure it will work excellent. I'm not running any choke, just another theft deterrent.
Thanks, Dave.
Ok, I'm ignorant.
Does not running a choke make the thief think the car won't start?
 
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