Thermoquad sizes

[garrett]

Has anyone of you tried one of the larger tq's on a 318 ? The one i picked up from my dad decodes as the 850 cfm model # 9053s however looking around the web i have seen the smaller one is only 50 cfm difference 1-1/2 vs 1-3/8 primary size. Anyway key point is i want a four barrel and throw the leaky 2bbl in the trash ! I have seen on here all the talk about 600 cfm for the small blocks but reading latley dodge put the tq's that are rated for 750 to 800 cfm on 318,340,360 im sure the 340 is a little different story but any info would be great !
Thanks guys.

[MountainMoparRobin]

your right on the sizes, I don't know if etsweptster will chime in but I believe one of the Thermoquads rated at 1100 cfm on the 440, so 2 600 cfm's could actually give you better mileage if you don't come across too many Mustangs or Camaro's I had a Quadrajet on my 340, and don't remember the size, it had to be pretty darn large for that 340 was a Big Block Killer, did you read over on http://www.allpar.com ? or also look in the tech area here: http://www.carburetor.ca/r

[quickd100]

There have been 3 sizes produced if you include the old aftermarket race model. 800cfm(1-3/8"primary bore), 850cfm (1-1/2" primary bore), and a 1000cfm, (1-1/2" primary bore with only single boosters in the primary bores). On any of the models you can alter the ultimate cfm flow by just adjusting the rear air door opening. So an 850 model my only flow 585(picked a number out of the air) by closing down the rear air door. At the same time you have to adjust the jetting as closing down the air door will richen up the A/F mixture.
It's really a shame that the thermoquad went out of production as it was the most advanced 4 barrel Carter produced and the most flexable. It offers great fuel mileage and horsepower potential.
One of the best tuning tools I own is an LM-1 meter, it lets you really dial in a carb. Using a 850 on a 318 will work but as I said you'll have to adjust the rear air door. If you don't have a supply of jets handy you can do it the rude and crude way. Rosin core solder and a set of numbered drill bits. Don't turn up your nose or laugh either, it will work just fine Dave

[MountainMoparRobin]

more info on the LM-1 ?

[Rodger]

Garret

If one is to measure the port size of the 2 bbl 318 carb and to measure the correct
carb's primary port size for a "Spread Bore" 4 bbl carb you will see the 2 bbl has a
larger hole that what the 4 bbl is using as a primary. This is the part of the reason
a 4 bbl carb gets better MPG while on the Free-way. The 2 bbl size and the primary
4 bbl size is a comperomise from the 2 bbl.

With the vacuum operated secondaries of the 4 bbl carbs this will permit the 4 bbl
user to only use what the present "fuel demand" is requiring. This is why it is
possible to have a more than a 400 CFM 4 bbl carb on the 318's. It is just some
"over kill" waiting to be used by a driver who thinks "that just some little bit more
will not hurt".

The other part to consider is 80% of the engine's RPM usage is around 2,000 RPM's,
not at 4,400 RPM's. This is true even if all you do is drive 1/4 mile at a time or
pull sled's at the State Fair.



Rodger & Gabby
COS

[quickd100]

more info on the LM-1 ?

It's wide band exhaust gas analizer. There are a number of different ones on the market, Summit and Jegs sell them. You have to weld in a bung on the exhaust and then install the oxygen sensor. With one you can set a carb up to it's full potential, good fuel economy at cruise and maximum hp at WOT. Dave

[garrett]

Wow, all very good info guys i love it ! I have an LM-1 i use on the race truck never thought to use it to tune a street drivin truck lol. I guess that why they call it thinking out side the box well im going to give it a try keep ya'll posted on the progress. Thanks again guys

[MountainMoparRobin]

more info on the LM-1 ?

It's wide band exhaust gas analizer. There are a number of different ones on the market, Summit and Jegs sell them. You have to weld in a bung on the exhaust and then install the oxygen sensor. With one you can set a carb up to it's full potential, good fuel economy at cruise and maximum hp at WOT. Dave

Can you tune your motor while driving? mounted inside the cab?

[quickd100]

more info on the LM-1 ?

It's wide band exhaust gas analizer. There are a number of different ones on the market, Summit and Jegs sell them. You have to weld in a bung on the exhaust and then install the oxygen sensor. With one you can set a carb up to it's full potential, good fuel economy at cruise and maximum hp at WOT. Dave

Can you tune your motor while driving? mounted inside the cab?

Yep, that's the beauty of it. Also one of the options is an rpm fuction. It gives you real time info on how rich or lean the motor is running. There is also a record function, you can download it to you computer at home, overlay previous runs. Up to that point, it was the best money I ever spent. I think my L&S dyno is the best money I ever spent on anything.Dave

[one54dodgetruck]

does anyone have any pros and cons with thermo quads? ive never ran them, and honestly only have seen them once or twice.

[garrett]

Well, my dad and grandfather and all there buddies have sworn by them since i was crawling on the garage floor. The ones i have used on big blocks all worked great however not to sure on the cons im sure the boys will fill us in on those. quick100 tell me more on your l&s dyno ?

[quickd100]

I bought a used Land&Sea engine dyno, it can handle up to 2000 hp. I've been in the process of getting it set up. I've run one mule motor one it so far to make sure everything worked. I've got a couple friends with 512's and a 484 wedge that are going on it shortly. My 528 out of my truck will be getting some time on it for some tuning this winter also. My son is having me build a 366 smallblock for his 65' Dart this winter so that will be getting broken in and tuned on it also. Dave

[MountainMoparRobin]

does anyone have any pros and cons with thermo quads? ive never ran them, and honestly only have seen them once or twice.

follow this link and read how to get 415 hp out of a 318 using almost all factory equipment, notice I said almost, cause they used KB pistons other than that all production parts, they used a THERMOQUAD for carberation http://www.popularhotrodding.com/engine ... index.html

[jimmy]

Like the guy's said the TQ is great when tuned properly, don't think you could go wrong.


Remember; the 4bbl will help on milage and power but you will not realize all potential until you change your cam to a factory grind 4bbl.
Headers or HP manifolds will also help a little.

I removed a leaky 2bbl and installed a Carter 625 4bbl elect. choke on a 79 Full time 4x4 Ramcharger with a bone stock 360 and auto. I never changed the cam but still gained power and milage. I went from 11mpg and always fighting to get it runing cold to 13.5 all the time and turn key down to minus 10 degrees. I had 3.54 gears and 32x11.5x15 tires. I felt I was doing pretty good. I always wanted to change the cam thou!

[truckluvr]

kind of a late post but I have thermoquads on all my early trucks! They are designed to only draw the correct amount of fuel for the given situation regardless of engine size. Heck they run great on /6's also. They are actually fairly easy to rebuild also. Unfortunately the rebuild kits are getting hard to find and spendy. Make sure that a rebuild kit is still available for the one your considering to buy. If you can find one for a 1973-6 360 or 400 with the 1 3/8" primaries will be best for all motors and (if your like me) a 73-4 440 TQ for that "oh the hell with fuel economy" option