Thermoquad

-

Scampin

Well-Known Member
Joined
Aug 27, 2005
Messages
382
Reaction score
292
Since everyone seems to be excited about thermoquads again I figure it's a good time to mull this over. What would it take to get a thermoquad to flow enough fuel to feed a 550+/- ish horsepower motor on E-85 or C-85? Also just for fun, what's the quickest 1/4mile anyone has run with one?
 
Its doable but it would definitely be a project that would take time and a lot of testing. Its not like a Holley where you can change a metering block and boosters.

The biggest issue I see is getting the booster outlet sizing correct.
 
Engine will consume a greater volume of E85 than non-E petrol, so you would definitely need to increase n/s size. I would go to 0.120" with your intended combo. You can drill the existing seats to the new size. Use a new drill to minimise the burr that is raised. You will need to smooth down the new seat. That requires a perfectly cylindrical tapered punch; or a small ball bearing also works. Tap lightly & check for leakage afterwards.
 
I had to make larger n&s when switching to q16 fuel. I believe I got .124 to seal, any larger and it would be inconsistent. Also required larger secondary jets. Most say you can make about the same horsepower on either, and E-85 is a heck of a lot cheaper. The class dictates factory intake, so 2 carbs is out.
 
Im guessing my 440 makes around 450 HP currently and the thermoquad has no problem running it nicely. I modded it years ago with the direction of a guy who used to be the thermoquad guru on moparts. The things i remember are drilling the primary and secondary jet sizes out. Drilling the pump shot squirters out, plugging the 2 air bleeds off in the front of the choke tower (not all Thermoquads have these, mine did). I also had my choke horn milled off for more airflow. This thing kicks *** on mine, i will say that! If yours doesnt make enough vacuum to hold the metering tree down at idle, you can clip the spring a little at a time until it works. The thing i can not remember is if he had me drill the secondary spray bars out or not and if he did, how much..
I plan on adding trick flow heads and a bigger cam in the future and will still be using my thermoquad.
 
Great to see a TQ 'kick ***'. Should be more of it!!!!!
The holes you are refer to in the choke tower. Are they the ones that intersect with the front two bowl screws? If so, they are for bypass air. Pretty sure these started with the 9000 series, haven't seen them on any 6000 series that I have hasd.
 
Great to see a TQ 'kick ***'. Should be more of it!!!!!
The holes you are refer to in the choke tower. Are they the ones that intersect with the front two bowl screws? If so, they are for bypass air. Pretty sure these started with the 9000 series, haven't seen them on any 6000 series that I have hasd.

I agree. I love them. I've been thinking of whippin one up for my slant six.
 
I know a bracket racer, runs low 10's /teens with a quadrajet. Not sure but probably race gas.
 
I believe some have run 9s with the QJ & there is NO reason the TQ couldn't!!
 
I believe some have run 9s with the QJ & there is NO reason the TQ couldn't!!
Bewy, what size secondary jets would you run on a mild to mid built 440? I bought several small drill bits years ago for building thermoquads per demonsizzler instructions and lost my notes. I have 2 drills for the secondary jets, a .147 and a .154, not sure which one i used.
 
First, make sure the secondary air bleed is 0.039-0.040" [ some were around 029, but every 6000 series I have measured is 040 ]. This is the brass tube that runs up the centre of the MJ. The pinched end pokes through the air horn. This pinched section is what you check/drill.

I would start with 0.137" sec jet. Changing the wide open position of the AV also affects rich/lean. I would set the AV at 29/64" & wind the spring to 2 turns, as starting points.
 
First, make sure the secondary air bleed is 0.039-0.040" [ some were around 029, but every 6000 series I have measured is 040 ]. This is the brass tube that runs up the centre of the MJ. The pinched end pokes through the air horn. This pinched section is what you check/drill.

I would start with 0.137" sec jet. Changing the wide open position of the AV also affects rich/lean. I would set the AV at 29/64" & wind the spring to 2 turns, as starting points.
well, this 9097s carb came factory with .143 secondaries..
 
Well start with those. These carbs come with 125, 137 & 143 sec jets, used on same size engine. Same air bleeds etc, same WOT sec blade position, so I'm not sure how the sec jet sized was selected.
 
-
Back
Top