View Full Version : Dual carb setup?
Anyone who can recommend what dual carb setup to go with? Need to order intake and 2x carb for my 302” -71 with cast iron heads.
chuckster
12-02-2018, 09:04 PM
Edelbrock sells a complete 2x4 setup less air cleaners for $1320. carlsfordparts.com sells a copy oof the original Ford setup with Holley 390 com carbs for $2150. They also have the Helling and Sterling air cleaners for $190. Take your pick. Just my$.02
http://carlsfordparts.com/parts_images/induction/289_302_dual_quad_induct.jpg
GFX2043mtu
12-03-2018, 08:25 PM
Be careful a normal 302 in no way needs two 4 barrel carbs and would easily over carb such a small displacement unless they are very small carbs. But then the smallest 4 barrel I know of made today is 450 CFM for a total of 900 CFM, way to much for 99% of all 302’s. Responsiveness and tunability will go out the door if not carefully selected. Dual 2 barrels mightbe ok but will still probably be more then needed. Now quad Weber IDA are nice but they are an entirely different animal then the standard American carbs. And you can get away with the higher CFM with them with out fuel condensing in the intake.
Duals on a street friendly 302? Very cool looking but from a performance point of view -- not a great choice for a street car. But if you're set on this combo stay away from a tunnel ram style manifold (individual runners with no common plenum) and get the smallest carbs possible. Even then I would expect this to be a poor performing street combo.
Before you pull the trigger on this; look at the total CFM needs of that diminutive small block and the total CFM of the smallest carb combo you can find. As GFX indicated above, there will be quite a large variance between what the engine needs and what you'll be feeding it. Use annular discharge boosters and mount the carbs as low as possible as you will surely have a problem with the vacuum signal to the boosters at WOT and this will help mitigate some of this issue. You may also have trouble covering a lean condition when you snap the throttle open from low speed. If you go this route I think you're going to be spending a lot of time tuning on this combo and may never be completely happy with it.
Good luck, and have fun. Whatever you decide you can always change it if it doesn't work out.
TexasAviator
12-03-2018, 09:18 PM
As others have stated the dual carb looks cool but is overkill. Not a route I would go but found you this. Do lots of reading and research, someone has done the combo and Fords are synonymous with fun outside the box builds. Check out this 302 Falcon.
https://www.hotrod.com/articles/dual-quad-ford-302-engine/
For the cost however, I went with a FiTech on a Victor Jr intake manifold and the car is insanely steady, well mannered, and gobs of fun to drive. Its like having the coyote with an old school look and about 50 more horsepower (in my 347, 302 based block). ;)
edwardb
12-03-2018, 10:19 PM
For the cost however, I went with a FiTech on a Victor Jr intake manifold and the car is insanely steady, well mannered, and gobs of fun to drive. Its like having the coyote with an old school look and about 50 more horsepower (in my 347, 302 based block). ;)
Appreciate your enthusiasm, but with all due respect, a SBF with throttle body EFI isn't like a Coyote. Loved my 347 too, and they're a great match for these cars. I promote them all the time for builders who prefer the old school look and sound. But the Coyote is really quite different in a bunch of ways, and have more power than you're giving credit for. Especially the newer Gen 2 and Gen 3. It's all good. If you haven't had a chance to ride in one or even drive, you should.
TexasAviator
12-03-2018, 10:31 PM
Not to get too off topic but not disagreeing with you. I was able to ride in one of the first Coyote Mustangs in my Area years ago. It is incredible even for the first generation. However the OP was asking about a very uncommon setup for a small CI motor. Its drivability is going to suck compared to anything really...
SSNK4US
12-04-2018, 01:28 AM
My old working at a speed shop days.... (and some pretty cool tours of Edelbrock, centerline etc)
Cubic inches x max RPM divided by 3456 (I know 3456 sounds funny) = ballpark carb CFM
Kurt
GoDadGo
12-04-2018, 08:37 AM
Just to run the numbers for you outlined by Kurt, here is what you are looking like from a C.F.M. perspective:
302 @ 6,500 RPM = 568 C.F.M. at 100% Volumetric Efficiency or 511 C.F.M. at 90% V.E.
frankb
12-04-2018, 08:51 AM
CS14: I, too, agree that 2 X 4's are too much for a street small block. However, if you really love the look, there are things you can do to make the system street friendly. As others have said, go with the smallest carbs you can find. Then set up the linkage as a progressive system with one carb's primarys opening to 40% or so before the other carb starts to open, then both reaching full open at the same time. Use vacuum secondary carbs and set the secondary opening (by changing the springs in the vacuum actuators) so that the secondaries don't start to open until mid RPM range at WOT. This setup is a lot of work and requires lots of attention (it changes with the weather!), but I agree that it looks great. If you don't mind the work, it's doable! :cool:
Frank B
GoDadGo
12-04-2018, 10:21 AM
I'm running an AVS-800 and am very happy with it since it is so easily tuned.
Would this system possibly scratch your dual carb itch?
https://www.jegs.com/i/Edelbrock/350/2035/10002/-1
Railroad
12-04-2018, 11:15 AM
I am thinking, Holley has a 390 cfm 4v carb. Using both, would be 780 cfm, which might be doable with a maxed out 302. I love the 2-fours look and would definitely consider locking out the secondaries to make it work.
SSNK4US
12-04-2018, 11:51 AM
Or you could use what I had on my 66 mustang.... but you’d have to pry it from my “on loan” neighbors 30 ford hands lol
It would look pretty cool under the hood of my MK4 but not very practical.
Also back in the day Holley made 390 cfm 4 barrel carbs... it was list-8007 I think. Not sure it they are still around. I’ll have to google them. But that was back when I was selling list-1850 600 Holleys all day long for $89 bucks lol
Anyway the 390 Holley was just like its 600 big brother, vacuum secondary’s, manual chokes and worked well on multi carb setups...
Blast from the past....., lol
Kurt
98586 98587
SSNK4US
12-04-2018, 11:58 AM
O. M. G. ! The 390 is still available, electric choke now but wow!! Over 500 bucks each!! But still a good solution.
Kurt
BEAR-AvHistory
12-04-2018, 12:11 PM
I am thinking, Holley has a 390 cfm 4v carb. Using both, would be 780 cfm, which might be doable with a maxed out 302. I love the 2-fours look and would definitely consider locking out the secondaries to make it work.
Not sure what you are looking at but vacuum secondaries will be easier to setup then any double pumper versions. Switched back & forth a few times with small Holly's on this one & eventually stayed with small Holly vacuum secondary carbs. Basic engine was a crate 1970 mechanical cam Small Block Chevy LT-1 @ 350CUI, TH 400, 9" Ford in a home built 33 Ford 3 window coupe. 2500LBS all in.
https://www.bimmerfest.com/forums/picture.php?albumid=14336&pictureid=56775
https://www.bimmerfest.com/forums/picture.php?albumid=9814&pictureid=45746
Very streetable for daily driving & a class winner at the annual Englishtown NJ Old Time Drags, still have the trophy:)
I just did a 351W build using Fitech dual quad throttle bodies on an rpm air gap intake. It runs very smooth and looks really cool. The efi does away with all the hassle associated with dual quads. Cost is not much more than a traditional carb setup either.
BEAR-AvHistory
12-04-2018, 02:47 PM
Or you could use what I had on my 66 mustang.... but you’d have to pry it from my “on loan” neighbors 30 ford hands lol
It would look pretty cool under the hood of my MK4 but not very practical.
Also back in the day Holley made 390 cfm 4 barrel carbs... it was list-8007 I think. Not sure it they are still around. I’ll have to google them. But that was back when I was selling list-1850 600 Holleys all day long for $89 bucks lol
Anyway the 390 Holley was just like its 600 big brother, vacuum secondary’s, manual chokes and worked well on multi carb setups...
Blast from the past....., lol
Kurt
98586 98587
Like the manifold. Back in the day we had one on a 64 Stingray 327. Might still have the picture. Also had one of those FORD style AF/X reverse entry fat tear drop shaped hood scoops to cover the carbs aircleaners.
https://www.macsautoparts.com/assets/macs/images/size/265x265/sku/64-79454.jpg
Had to fabricate the carb linkage out of bits & pieces that came in some kind of a kit. PITB
GoDadGo
12-04-2018, 03:07 PM
A Cross Ram Would Be Super Cool Sitting Under A Super Snake Style Hood!
chuckster
12-04-2018, 06:15 PM
Carl’s sells the 2 x 390 cfm 4v Holleys on a ford aluminum manifold. I ran this setup on my old 1967 GT350 ran super. Fast and predictable. Carl’s also sells an old school “trips” setup, 3 x 2v holleys with a progressive linkage. I ran this setup on that same GT350, when it was “dialed in” it was great, got 20+ MPG on the highway. 98628However it did not like staying “ dialed in”
BEAR-AvHistory
12-04-2018, 09:00 PM
One thing that did not come out is manifold usable RPM ranges. A lot of 2X4's are large plenum high RPM units. They are crappy street drivers under 3500RPM in a lot of cases. There were early small block Chevy & Corvette factory 2X4 street models 265/283/327 back in the mid 1950's & up with small plenums & longer runners with good low end torque & nice upper range power.
Was not much into FORDS then & don't know the product lines but do know the "57 T-Bird 312 had 2X4 as a factory option. A similar type manifold 1500-6000RPM working range should be good to go. Getting a factory FORD unit would be a very big bucks deal but the after market was selling a lot of "better then stock" 2X4 manifolds so low end units should be available at reasonable prices.
A FORD Trans Am type unit would likely be a problem on the street same as a 302 Z-28 2X4
A pair of 390's will work & with vacuum secondaries, the secondaries will most likely never full open.
chuckster
12-09-2018, 06:09 PM
Anyone who can recommend what dual carb setup to go with? Need to order intake and 2x carb for my 302” -71 with cast iron heads.
If you do a search on the Facebook marketplace for “dual quads” someone is selling a complete 2x4 setup complete with Holley 390s and a cobra air cleaner. Someone is going to get a hell of a deal.