The best carb is the one that is of the CORRECT SIZE FOR THE ENGINE CUBES,CORRECTLY JETTED,RUNNING THE INTENDED FUEL IT WAS BUILT TO USE PERIOD! Every other opinion as to what is supposedly better is usually based on the users overall experience and level of comfort or lack thereof, of what type of carb they want or like to use ,and that is the probably the worst way to choose anything in life! Going outside your comfort zone may be hard ,but usually garners the greatest results There are countless example of multiple types of carbs achieving the desired results the builder had intended, so this is a loaded and pointless question
i agree with you on tests i read they all have good and bad points, but the question was what carb do you like, not what one is the best or runs the best.
They type of carb does make a big difference in driveability and response not just size. A 1000 cfm ThermoQuad is a totally different animal than the 1050 Dominator. In street driving the 1000 ThermoQuad is much better and can run right with a Dominator at the track but the Dominator is pretty simple and easier to deal with on a race car.
I ran a TQ on my old 69 STG 1 , it had a low comp 455 with a c118 camshaft . Of all the carbs I tried the TQ was tops for perf. I think mine came off of a mopar , I just kitted it & tuned the mettering rods . Does anybody offer these carbs on the market today ? ick
I havent seen alot of t/q on race cars lately? Also like i said, the correctly sized carb is just that,the one that will deliver optimal performance throughout the engines entrie operating range Also if its a street car,then you still can ,with some work,make the properly sized venturi along with the proper booster deliver on your goals I think you can achieve simjilar mileage from most carbs if they are tuned correctly for it they all operate basically thesame way Some are geared more towards mileage from the factory,but they all have a idle,(some intermediate) ,transition,main metering and power enrihchment circuits so they all can be tailored to your application So also,if you put too large a carb on your motor ,and wonder why its undriveable,unresponsive/under performing then you just proved my point:TU:
Alot of the reason you don't see Thermoquads on race cars is marketing and the fact they haven't been made for years....... The Dominator has 4 big throttles that flop right open. The Thermoquad has an air valve secondary. Allows a smaller motor to run a bigger carb. I put a "too large" 800 Quadrajet on a stock 350 and it ran great by tightening the air valve some. I'm just saying size isn't all that matters.....:Brow:
I agree that a holley will give you more power at WOT,thats why so many racers use them. But the fuel bowls always leak,and the power valves can fail.The afb is the easiest to tune, and cant leak because of the design. They dont get great mileage.The Q jet is the best all around street carb..
holley 600 cfm for gas mileage.....with vac. secondaries......Got a 425 riv that gets 18+ per gal... holley 675 cfm..... holley three barrel for power..... with vac. secondaries.....950 and 1050 cfm.... heck ,,, any ol holley..... after that ,,, Webbers.....
Can I prefer fuel injection even though I don't have it on any of my older engines? it is indisputably the best for everything but simplicity. Pricing is beginning to be competitive with a new "custom" holley derivative after some careful planning. From my observation it's probably not a lot more time consuming than properly dialing in a carb for a good fuel curve at both WOT and cruise when starting with a new undeveloped combination. At least after conquering the first install. Second to that is the Thermoquad, if only parts were readily and economically available. it was the last newly engineered carb and Carter had a lot of experience to invest in it. it's a PITA to rejet (excepting primary metering rod changes!), but once done you are done. As is the Q-jet. Watch for cracked plastic float bowls that leak down and flood the engine when parked. The Q-jet was widely available, cheap at the junkyard thanks to the huge production numbers, and had great mix of performance and street manners like the TQ. Install a brass float thanks to Ethanol if for no other reason. Always re-seal the main wells; JB weld doesn't work anymore. Edelbrock saw the merit of reintroducing the Q-jet but price and all the old nicknames from heathens scared many away to a cheaper AFB or Holley. It's been used and properly tuned by the factory for everything between a 241 V-6 to a super-duty 455 Pontiac and even the 428 Super CobraJet Ford. It and the TQ are more complicated because they are much more adjustable for a wide variety of applications. Holleys are easy to tune for arguably unsurpassable WOT performance. That's about it. it is a racing carb adapted to the street. Can it be made to work on the street? Sure, but it will not be as diversely flexible as a high-performance street carb compared to the Q-jet or TQ. AFB is not the fastest, or best mileage, cheap to buy new, and always, always seems to work without any special fixes. The AVS is a little better but it's no Q-Jet!
I recently converted a 9375- 1050 cfm holley dominator to a 2 circuit that has now become my all time favourite. Its very streetable, crisp and doesn't load up at part throttle like the 3 circuits carbs do at part throttle. I's all about the right tune to get the best burn of fuel for your combination. Tom
Tell me more how did you do it? Does it still work well at the track? I would think the rich mid circuit that causes the lumpiness on the street at light load is what make them leave the line so well....
I run an edlebrock 850 on my GS 455. Hands down its the best carb Ive ever used on any car. Just Bolt it on and go. 10 years and no problems and it still starts easy, electric choke works flawlessly, My GS runs better than any car in my driveway including the fuel injected ones. The old q jets were a total pain and I spent more money on the weld plug repair kits rebushing throttle plates and rebuild kits than the cost of the no fuss edlebrock, which by the way worked way better than any q jet I ever had. I get the hardcore racers will never give up their q jets, but for the street, the edlebrock is the way to go. :3gears:
In my opinion of owning my 1970 GS 455 Stage1 for 43 years & I have tried every carburetor imaginable from Holley; 1000 cfm Thermo-Quad; 9800 Thermo-Quad, the later model Q-Jets up to 1974. I will say the best ones are from 1969 thru 1973.When I first began to modify my original Q-Jet, there were quite a few upgrades from Baldwin Motion to shorten the secondary engagement rod to enable quicker opening of the Secondary circuit. Trust me, this shortened secondary rod really did the trick. There were primary dash pot modification with would enable faster opening of the secondary circuit. Finally, after experimenting with the float level along with the needle & seat offrice sizes; primary metering rods & jets. I reached the conclusion to only increase the primary metering jets to 2 sizes up & deal with the ignition curve to have a true all around performing carburetor that would give decent gas mileage along with great performance. The only downside was the fuel wells leaking fuel which could be easily repaired.
I converted to a 2 circuit for better low speed and cruising to eliminate the pig rich condition between 2000 to 3000 rpm. The carb was doing the opposite to what it should have. Dribbling fuel at part throttle and leaning out at the top. You want to have a controllable idle and crisp transition to the power circuit. The power circuit is only 1/3 of the combination of an effective carb Check out the Motorsports Village site for their steps to this conversion. Many have reported better and more consistant times with 2 circuit over custom shop 3 circuits. I don't have an o2 monitoring system but used the base recipe for the conversion as follows and it's in the ball park: I used two old 2 circuit Quick fuel billet blocks trhat i had lying around Emulsion holes 1 & 3 open at .028" 2 & 4 blocked Primary power valve, 4.0" to 4.5" high flow Power valve restriction jets at .089" (PVCR) Pri jet 86 Secondary jet 93 to 96 with external extensions Solid plug secondary .040 Idle jet restrictions Angle channel drilled to .159 Main body mods: .025 Main air Bleed (MAB) .076 Idle air Bleed (IAB) in a two circuit conversion the intermediate becomes the idle air bleed. .0595 Restriction in to the vertical transition slots in the venturi (TSJ) Important to restrict these Works well with the 464 using pump gas. No more black plugs from puddling fuel dripping out from the 3 circuit. Instead its atomized Top end is good with the mods Tom
I run a High flow PV only in the front, but I street drive my combination. Some of the 2 circuit converts keep both plugged and square jet. It's not essential to have a PV on a 2 circuit. Why a 2 circuit convrsion? Because it's easier to tune for in between wide open & idle. Even doing a burnout requires only part throttle. So essentially you could foul plugs prior to take off. Below, Lots of reading on powervalves & jetting http://www.motorsportsvillage.com/forum/viewtopic.php?f=6&t=8687 http://www.motorsportsvillage.com/forum/viewtopic.php?f=6&t=8245 Tom
I use anEdlebrock thunder series 850 on My GS 455. Works perfectly out of the box. electric choke works flawless. 10 years and never been apart. The Q jets work fine when they are not worn out but 43 old castings get worn,cracked, leak and get tempermental and it takes a skilled and patient rebuilder to get them right.ou:
