@68original Because I have a Max Wedge and I can too! Then you add fenderwell headers! Nuthin' like the sweet sound of a 4 barrel carburetor exceptin' if you have TWO 4 barrel carburetors!
Why run dual quads?
- Thread starter halfafish
- Start date
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..because I can! Nothing like feeding each cylinder an equal mixture.
A well setup and tuned multiple carburetor setup is a kick in the *** to drive. But in the same vein, some people think if some is good MORE is better and they go overboard with big CFM units, not tuned well to the point of almost dripping gas from the exhaust pipes of the vehicle.
harrisonm
Well-Known Member
Hey, @coloradohill, did your hood close over that 6 Pack setup. I have seriously considered a 6 pack for my 69 340 Barracuda, but I don't want to install a scoop.
The question to ask is "Why shouldn't you run two carburetors?"
mopardude318
Well-Known Member
Another reason why. Kind of a must.
And two Thumper carbs to boot! That is wicked Man!
matthon
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I've run 3 different intakes with 4 different carbs, or 5 plus efi, depending on how you look at it.
Built 383, began with a tunnel ram and two Holley 390s.
It was ok, slight hesitation at go, drivable, made great hp/torque. Just didn't like those carbs for some reason.
Switched to a Torker II single with an 850 Holley. Not a fan, zero low end. It's Torker II iirc.
On to a Performer Plus and the 850. Really snappy off the line, a real head jerker compared to the T II, obviously.
I felt there was more to gain, went back to the tunnel ram, this time with 600 Holleys. I've said it before, a different animal over the 390s. Great carbs, almost no hesitation at go, if any. Really woke it up at high rpm and had the low end seat of your pants to boot.
In both cases with the carbs, both were vaccum secondary, 1:1 throttle.
Still, more was there. Went efi, different species. The throttle bodies are enormous, and the fuel sprays out in a tornado style. Zero hesitation, pulls the entire way.
I don't even have full throttle with the efi, have been driving for years this way, keep meaning to address it but I never 'need' it while driving, and always forget about it.
Could have probably got similar results with dual double pumpers, but efi starts first try no matter what, no chokes, can tune via controller, fuel pressure only present when key is on, and the return springs are on the tbs, hello carb manufacturers take note.
Recently went to timing control and bonus, the car runs cooler in all types of driving and weather, not sure why.
In all cases I drove regularly, daily, all over, short trips, long distances, you name it, still do.
The Weiand tunnel ram is fantastic too, and I ported it slightly at the beginning so it flowed nice and free top to bottom.
Built 383, began with a tunnel ram and two Holley 390s.
It was ok, slight hesitation at go, drivable, made great hp/torque. Just didn't like those carbs for some reason.
Switched to a Torker II single with an 850 Holley. Not a fan, zero low end. It's Torker II iirc.
On to a Performer Plus and the 850. Really snappy off the line, a real head jerker compared to the T II, obviously.
I felt there was more to gain, went back to the tunnel ram, this time with 600 Holleys. I've said it before, a different animal over the 390s. Great carbs, almost no hesitation at go, if any. Really woke it up at high rpm and had the low end seat of your pants to boot.
In both cases with the carbs, both were vaccum secondary, 1:1 throttle.
Still, more was there. Went efi, different species. The throttle bodies are enormous, and the fuel sprays out in a tornado style. Zero hesitation, pulls the entire way.
I don't even have full throttle with the efi, have been driving for years this way, keep meaning to address it but I never 'need' it while driving, and always forget about it.
Could have probably got similar results with dual double pumpers, but efi starts first try no matter what, no chokes, can tune via controller, fuel pressure only present when key is on, and the return springs are on the tbs, hello carb manufacturers take note.
Recently went to timing control and bonus, the car runs cooler in all types of driving and weather, not sure why.
In all cases I drove regularly, daily, all over, short trips, long distances, you name it, still do.
The Weiand tunnel ram is fantastic too, and I ported it slightly at the beginning so it flowed nice and free top to bottom.
an STR -12 has looong runners inside that are as long as most tunnel rams. Long runners means column velocity and steady ram pressure. To make this work you need a right carb to feed the left bank and a left carb to feed the right bank, just like the factory Max Wedge and Hemi crossrams.
This is why I have never been excited about the Offy inline 2x4 manifolds - VERY short runners.
Most of the old Mopar factory in line two 4 manifolds were dual planes with longer runners, as were the Edelbrock D-64/D-66 and their big block version which is still available.
As the quote below says, in my experience I have never had to spend a lot of time tinkering and tuning my dual quads. I have 2 500 Edelbrock AFBs on this motor):
This is why I have never been excited about the Offy inline 2x4 manifolds - VERY short runners.
Most of the old Mopar factory in line two 4 manifolds were dual planes with longer runners, as were the Edelbrock D-64/D-66 and their big block version which is still available.
As the quote below says, in my experience I have never had to spend a lot of time tinkering and tuning my dual quads. I have 2 500 Edelbrock AFBs on this motor):
coloradohill
Well-Known Member
@harrisonm , I have read several posts about six packs fitting under hoods on this forum.
Several said yes so, I tried it. Now mine is only temporary and I still have the hood for the t ram on my car.
It fits but I would like to see a little more space. I’m running spool mounts and could probably lower the engine some to make room.
I am using door edge protector on the cut out area of the hood and would gain a little clearance without it.
famous bob
mopar misfit
not so my freinds, a young guy thats the son of a freind and ex racer that I used to race against , has a 340/? , runs 2 fuel ingition 4 barrels , runs 10:40`s ,and goes on the power tour about every year , was runner up at this yrs. , mopars in the park here .
Newbomb Turk
Well-Known Member
Yup. And then people started to figure out that you could put two even bigger carbs on most stuff, tune it correctly and make even more power.
If I was the OP I’d use two 750 double pumpers and not look back.
Good info and lots to drool over, thanks to all! I'm not smart enough to tune any carb much less multiples, but it's fun to think about.
I was the same way with carbs, and "packed it in" for now as I wanted to go to Moparfest, sadly missed that tho.
perfacar
Well-Known Member
that question has been asked many times, on a factory dual four versus singe four is worth .four tenths faster. chev had dual fours on 56 , 265 and the 283, mopar had them on 318 poly, 354 hemi, 392 hemi, the 62 413 and 383 , ford had them on 427 FE. i know this, when you punch open dual fours, has way more response. i had them on my old 265 chev, planning on putting them on my 273 later this year. all these setups had progressive linkages. fuel milage was bout the same , till you stepped on it. just food for thought.
Another thought on the topic is just throw yourself in with the wolves. If it runs crappy, learn to tune the carbs until they work. I got mine working amazing - anyone can. Do the research, ask lots of questions when in need, and tinker until it works. It took lots of reading and finding a key few people that can explain things. Making it work is a huge win and feels great. I wouldn't change anything - other than more compression, better heads, bigger cam, more converter, less weight, better shocks........
I just looks cool and runs great that’s why I have them on my desoto. I put o2 censors on it and tuned the carbs, I’m happy with it. It does have a quick off/on point a low RPMs. Offy intake with crossram adapters, 500cfm eddys on a 408/4speed/391s
Dale Davies
Well-Known Member
Back in another lifetime, there was only 1 barrel carbs. So to get more airflow people built 2, 3, 4 and 6 carb manifolds.I was doing a little thinking-over-coffee this morning, and while perusing some threads where dual quads were a topic I came up with more questions than answers. In a nutshell, why would a person want to run dual quads instead of a single carb? For sure there is the coolness factor and visual appeal but otherwise what's the benefit? If running a pair of 600 CFM (or whatever size) carbs why not just run a big single 4-barrel?
Enquiring minds want to know...
Will Carter was an early tinkerer and inventor when fuels were of questionable quality at best and many carburetors no better. He designed and built a 1 barrel updraft carb that worked better. A great inventor but not so goox at looking after the finances, he sold out but stayed working for the company.
In the 1950's, engine displacements were getting larger and roads better quality. To supply that required more air and fuel. Thus the Carter WCFB, Will Carter Four Barrel, carb was developed. Shortly later Rochester introduced the 4G and 4GC carbs. The WCFB's were rated at 385CFM. On the Chevy Corvette 283 they wanted more, so installing 2 x 4 carbs was the hot ticket. Then engine dislpacements went to 400+ CID. For the bread and butter engines a 2 barrel carb was good enough but the next step up was a 4 barrel.
Then we got the 389 Pontiac GTO's and Ford 390's with 3 2 barrel carbs that ran most of the time on just the center carb and with progressive linkage opened up the front and rear carbs. Then with the 427 or 7 liter engines dual 4 barrels with progressive linkage provided the airflow. With this there is a primary and secondary carb. So putzing around town you are probably running on the primary carb primary throttle bores only. With the fairly small throttle bores and venturis, the air is moving quickly which promotes atomization. As you want a bit more speed or power, the secondary carb primaries start to open. The airflow remains high and fuel economy is still pretty good. As you request more the primary secondaries open and then the secondary secondary throttles open. This is all mechanical linkage.
With vacuum operated secondaries, the primaries are probably progressive to give that goid fuel economy and easy staged application of power. The secondary vacuum pots can have the same springs or slightly different to stage their opening.
With a single large carb driving on the street, airflow through large primary bores is slow so atomization and fuel economy suffer. On a race track the single is fine and may actually put out more power even if the airflow capability is the same.
So application and personal preference dictate the choice.
Many Dodge trucks had 354 Hemis with 2V carburation. Simplicity, low RPM and fuel economy under high loads. Lots were farm trucks with dump boxes.
canyncarvr
Well-Known Member
I put a dual quad on my car when it had a '73 340 (low comp smog motor) in it. Used two out-of-the-box Carters, 650 AVSs IIRC. Progressive linkage. From sea-level to 4000' el. never had a problem starting or running. Got over 20mpg on the highway. Drove it cross country at least once.
Had no problem with no thing about it. Throttle response was perfect...no bogs, lags, stumbles or any other issue.
That was with a manual trans and 3.23 rear gears.
DID get waxed by a Boss Mustang once. That was at 4000' el. with a trunk full of car parts (I mean full...including the OEM intake manifold), and two passengers...each of them 6'+ big guys. If you have to ask why, you were evidently never young and stoopid.
OR, maybe I was just stoopider. There is a very high chance of a pegging the truth-o-meter on that possibility.
Have a sibling that drove it some. She said NO one came close to HER racing in town. I don't know about that, but she swears it was so. No, I had no idea she was pulling them kind'a stunts with MY car. Trunk probably empty...and her AND her buddy wouldn't have weighed much more than just me...if even as much.
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Dale Davies
Well-Known Member
Good reason to join a local car club and get to know people's expertise. Usually willing to help and explain what and why. You buy the pizza and beers.
Eye Candy
60-70's Bravado
When have you seen a dual quad engine , and NOT thought hmmm
Must be built
Car manufacturers knew the WOW factor of dual carburetion
57-61 Caddy 2, 4's AFB
57-61 Corvette same WCFB's
57 Olds 371 Tripower Rochesters
58 Chev 360 hp 348 Tripower same
Pontiac Tripower same
Ford Dual quad 427 Holleys
Ford Tripower 406/410 Holleys
340, 440 Six pack
425 Nailhead Buick 2X AFB
Hudson Hornet 2x1's (ruled Nascar early 5O's)
Etc etc
Efficiency
62. 383 Dual AFB,
Single carb 330 hp
Duals. 343 hp
For multiple carbs, great for show and go
My desire
Complete top end Trick Flow kit with
Single Competition Series 1000 CFM
Thermoquad ( modified)
60-70's Bravado
When have you seen a dual quad engine , and NOT thought hmmm
Must be built
Car manufacturers knew the WOW factor of dual carburetion
57-61 Caddy 2, 4's AFB
57-61 Corvette same WCFB's
57 Olds 371 Tripower Rochesters
58 Chev 360 hp 348 Tripower same
Pontiac Tripower same
Ford Dual quad 427 Holleys
Ford Tripower 406/410 Holleys
340, 440 Six pack
425 Nailhead Buick 2X AFB
Hudson Hornet 2x1's (ruled Nascar early 5O's)
Etc etc
Efficiency
62. 383 Dual AFB,
Single carb 330 hp
Duals. 343 hp
For multiple carbs, great for show and go
My desire
Complete top end Trick Flow kit with
Single Competition Series 1000 CFM
Thermoquad ( modified)
Last edited:
Dale Davies
Well-Known Member
Yes they did. By then the WCFB's were on the way out but still used on small blocks. The 409 would have had a pair of Carter AFB carbs. Probably 500CFM but possibly 625CFM carbs.
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