Dual-Quad, Big Carbs? • The Dodge Challenger Message Board

by **Misaeus** » 10 Feb 2007 17:45

for an average 440 with a single carb most people recomends a 750 cfm carb.
for more of a strip use a 850 is generally suggested.

why for a dual-quad (or tunnel ram) a pair of 600-650 cfm carbs usually are indicated?

for the CH-28 Dual-Quad intake manifold (for a 440 engine) Edelbrock recommends a pair of 600 cfm carbs for street use.
in this combo with a progressive linkage while cruising only the primaries of the rear carb are in use but at full throtle comes a total of 1200 cfm.

in the 440 Six-Pack cars a total of 900-950 cfm (in 4bbl numbers) are available at wot but while in cruise only the center carb works with a cfm rating of 230-250 (4bbl equivalence).

so, in a dual-quad application why not just use a pair of 390-450 cfm carbs?
with a non-progressive linkage the primaries of the two carbs can flow more than the center carb of a Six-Pack i think, and at wot a total of 780-900 cfm is at hand matching the ratings of the suggested single carb combos...

by **Eddie** » 11 Feb 2007 0:05

I think basically, it's outdated "eye candy"!! Don't get me wrong I love multi-carb setups, they just arent optimal unless you use a single plane intake such as a tunnel ram,(pro-stock). That dual plane and feeding it more fuel against the restriction,(dual plane), makes it "easy" to over carb unless you have enough engine to pump it. They can be "made" to run but are a potential tuning nightmare for people that have the chronic affliction More's Law. Some's good MORES Better!

by **Misaeus** » 11 Feb 2007 3:12

thanks for the reply!

i just started the rebuild of my 68 RR in an old school style. you know, Cragar S/S rims, Grant Classic steering wheel, Sun tach...
and dual-quads are natural for a 60s to early 70s build...

my 440 was built with a 71 0.30 over block, stock steel crank and rods, TRW Six-Pack flat tops, ported and polished 906 heads with 2.14 and 1.81 valves, Hooker Comp headers, Torker 440 intake and a Holley 750 vacuum secondaries carb.
the cam is an early 70s Crower hidraulic. i don't know the specs but it feels powerfull.
the estimated compression ratio is 9:1. i'm thinking in mill the heads to raise it to 10-10.5:1.

the trans is a full manual 727 and the gears are 3.55.

the previous owner claimed 12.79 @ 108 with 275/60 drag radials and 3" exhaust (currently 2.5").

i need to replace the headers and i plan to swap the cam for a solid and to add a dual-quad setup.

i mentioned the Edel CH28 for its recommended carbs but i'm thinking in an Offenhauser dual-quad intake that is period correct and offers more flexibility with carbs and air cleaners.

with the Offy i can use Holley carbs mounted in line or sideways (they have adapters and linkage for sideway use) or Edel/Carter carbs.
and even cross ram adapters...

possibly the CH28 made more power since it's a more modern design similar to the Performer RPM, but i like the Offy...

the Offenhauser dual-quad intake manifold is a low rise divided single plane design. cutting the divider lower or/and adding an open spacer can make it more of a single plane i think...

regarding the carbs at Summit Racing the eddy 500 (manual choke) is priced at $230, the 600 (manual choke)at $235, the Holley 390 (vacuum, electric choke) at $336, the holley 450 (mechanical, no choke) at $226, Holley 600 (vacuum, manual choke) at $236, Holley 600DP (mechanical, manual choke) $320. the prices are close...

by **dave-r** » 11 Feb 2007 18:52

One problem with dual carbs is fuel distrubution at anything other than full throttle. You can end up with the engine rich at one end and lean at the other under normal driving throttle positions. In particular if the velocity through the carb and manifold is low.

Many of these dual carb/dual plane designs are not good performers on the dyno. They are a compramise to make the dual carb set-up streetable.
Open plenium/single plane manifolds work well at very high rpms. Which is what they are for. Dragsters that launch at 4000rpm and more.

If each cylinder can "see" the whole of each carb then the air coming through the carbs is going to be VERY slow so fuel drop-out is going to be really bad.

I agree it seems silly to suggest that you need 2 x 500 cfm and bigger carbs. But if you use vacuum secondaries (and the Edelbrock performer has a airflow controlled flap in the secondary side) then you will be probably only be running on the primary of each carb anyway.

But if you are building the engine for looks over anything else then build it any way you want. There is nothing wrong with that.
Just don't be suprised if it does not run as well as a good intake and single 4bbl. Expect very poor MPG as well.

by **Eddie** » 12 Feb 2007 0:17

Man, those offy's ROCK! Eye candy, it wins hands down! Dave is right of course but that setup you want to pursue looks bitchin man! May I give you a little tip/advice. I too am "runnin'triple two suckers" SIX PACK on a 440 with the factory dual plane intake. The "problem" with Holley 4160 type carbs on a six pack is you have to increase the orfice to get more fuel into the airstream. I didnt want to drill anything and there is a shop that specialises in multi carb steups with both dual and single plane street or Race applications. It's called Pro-Max www.promaxcarbs.com and they sell metering plates for accepting Holley jets and makes tuning much easier and more precise. Hey, I need all the help I can get! Maybe they can give you some good advice on what setup works best, Ben Gorman or Scott Petrusky also their phone is 317-484-1451.

by **dave-r** » 12 Feb 2007 12:02

Good reply Eddie. :thumbsup:

by **Misaeus** » 12 Feb 2007 23:30

thanks too much guys!!

my car is neither a show car poseur nor a race car. it's a (powerfull) street car used in weekends 2 to 3 times a month and see occasional strip(and street) action.

i aways liked the dual carb setup but my idea isn't looks over all other things. need to combine looks with reasonable function.

if it doesn't work i just can use a single carb an still stay in the theme...

(Dick Landy's 68 Coronet)

my only concern is since i'm a poor man i can't try the different options.
i need to decide and do it right the first time...

how the stock dual carb Street Hemi works?
i think it uses a pair of 625 Carter carbs in a dual plane intake.
has it solid or progressive linkage?

by **Eddie** » 13 Feb 2007 0:29

Progressive. on the AFB's, 426 Hemi. Keep in mind that was the sixties. Holley has a lot of tuning parts much more than the afb/avs series. And we didn't mean to discourage you man, it;s just dont expect more from it than lets say a hot 440 with an INDY 4150 single plane and a holley 850 DP. The 440 can be made to run easier than the Hemi which is a big port engine. I just spent over 1k to get my sixpack and dual plane to "act' like a tuned four barrel on a single plane, close ,but not even on the same level really, like Dave said it's awful hard to get that restrictive dual plane to handle large quantities of air and fuel. I think the "hot" setup would be an INDY dual plane 440-3 with a Holley Dominator, four corner idle, adjustable bleeds, and of course power valves for street use. Those D/P INDY's can flow as much as many single planes. But if two four's trip yer trigger that's cool. Yeah man, Dick Landy, :s005:

by **Misaeus** » 13 Feb 2007 22:03

sorry

was not my intention to say you are trying to disencourage me.

sometimes is not easy to express yourself in a foreign language...

your information is very usefull to me and answered a lot of questions!

thank you

by **Eddie** » 14 Feb 2007 2:36

Actually your expression and conveyance exceed most Americans, at least where I live! :thumbsup:

by **dave-r** » 18 Feb 2007 16:57

Hey RoadRunner68.

I know a guy who is selling a 440 Weind tunnel ram and a pair off Holley 660 centre squirters plus linkage, fuel inlet pipes, and chrome stacks.

Excellent condition. He says these type of carbs are the best combination for a tunnel rammed 440.

He wants £500.00 which I thing is real cheap.

If you want the contact get in touch with me.

by **Eddie** » 21 Feb 2007 1:31

Also Roadrunner68 have you investigated the dual plane INDY 440-3 I think it is called. It can exceed 375 CFM per port and is setup for a Holley 4150 style carb. This flow can easily support 600 H.P. and would possess great throttle response. Mopar Muscle magazine built a 440 with it and INDY EZ Heads and made well over 600 H.P. with a dual plane to boot! This is extraordinary for a dual plane to make this kind of power with a streetable camshaft! I know you want multi carbs but I thought I would let you know of this pretty remarkable piece.

by **dave-r** » 22 Feb 2007 21:55

Where is he? He is missing a real bargin. Those carbs are worth $800 each.

I will send him an email. :roll:

by **Misaeus** » 23 Feb 2007 3:34

thanks Dave, the offer is interesting

the Tunnel Rams are cool but for my car i prefer an under hood combo...

also is not my priority. just making a plan to the things to come.

need to fix some suspension/brake/steering issues first...

thanks Eddie

i know the Mopar Muscle article. the intake was heavily ported and opened to Max Wedge ports by a pro to flow an average 360 cfm.
it flowed 300 cfm out-of-the-box, not much more than the Performer RPM 280 cfm, but the RPM cannot be opened to Max Wedge ports.
its not cheap...

i'm expecting 500 hp maximum with no exotic parts such as Indy heads, 1.7:1 rockers to 600" lift, Main Stud-Girdle...

i think i finally go to the Eddy dual-quad with the recommended Eddy 600 carbs and progressive linkage. the intake even come with the correct jets for the carbs...
a "Street Hemi" 440 setup...

i need to figure the other components to match this combo.
have some limitations: 906 heads, pump gas, 3.73 gears as the only option, alot of city and highway cruising...

by **dave-r** » 23 Feb 2007 10:39

Thats a shame you don't want this set-up because the carbs are modified to actually work well with the runnel ram and it would look mean as hell on the the car.

by **dave-r** » 23 Feb 2007 11:59

Here they are.

Go on. You want them really don't you? :lol:

by **christer** » 23 Feb 2007 14:12

dave-r wrote:Here they are.

Go on. You want them really don't you?

Do you think you can you post a hi-res pic of the calender girl, Dave? Please?

(Sorry, I think I am in the friday-afternoon-mood :mrgreen:

)

by **dave-r** » 23 Feb 2007 15:25

I must be strange because I think the tunnel ram is more sexy.

by **Eddie** » 23 Feb 2007 16:03

Me too Dave! And you know the dirty ol man I am!

by **dave-r** » 23 Feb 2007 16:17

I sometimes wish my car was not a real numbers matching R/T because I would love to cut the hood to mount those. :twisted:

by **Eddie** » 23 Feb 2007 17:12

I wouldnt either Dave, BTW, is it difficult to obtain an fiberglass one then you could cut away. Or would that be an expensive "hole"? :oops:

by **christer** » 23 Feb 2007 19:13

dave-r wrote:I must be strange because I think the tunnel ram is more sexy.

How the **** can an eight-barrel setup be sexy? :s022:

No question about that a six-pack setup is very sexy though :s005:

(Sorry)

by **dave-r** » 23 Feb 2007 19:30

Its the induction roar when you hit the throttle.

You can hear the air sucking down the carbs because they are outside of the engine bay and you can see the carb linkage moving etc. They just scream MUSCLE! :twisted:

by **christer** » 23 Feb 2007 22:00

dave-r wrote:Its the induction roar when you hit the throttle. You can hear the air sucking down the carbs because they are outside of the engine bay and you can see the carb linkage moving etc. They just scream MUSCLE!

You really have a point there, Dave!

It all reminds me of a black Challenger with red´n yellow stripes that ruled the streets in the eighties. 440", dual quads, wide tyres, loud pipes.... Remember those days? I don´t find any pic´s of it right now but I found another pic instead. It is from Power meet, year 2000 or something.

by **Misaeus** » 23 Feb 2007 22:45

by **Eddie** » 23 Feb 2007 23:00

Awesome pics Roadrunner68! Wonder what the blonde chick is thinking? Those pics really take me back, do it man, go with the dual quads!

by **Misaeus** » 24 Feb 2007 1:09

airfuelEddie wrote:Wonder what the blonde chick is thinking?

"my man think only one thing, this big, noisy, smelly, shaking engine... but at least he isn't thinking in other women..."

by **472 R/T SE** » 24 Feb 2007 2:53

I've gotten 13 mpg a couple times on my way to Seattle. The Stage 5 intake (single plane) I'm running is the only way to go. The carbs are spaced apart a lot more than factory as well with "solid" linkage. Crisp response coming off a stop and plenty of giddy up to spare. I know all the rage is the dual plane intake but there's no way I'd ever go that route on a modified car again.

Of course it doesn't matter what I think...but I would jump all over that tunnel ram set up Dave is offering. Nothing says old school more than a couple carbs at eye level. :thumbsup:

And that's one he!! of a price.

by **Eddie** » 24 Feb 2007 10:56

You are right 472, I run an MoPar M1 Single plane with Holley 4150 750 DP and the 292/509 Mope cam with 74 degrees overlap 380/360 magnum in my TRUCK! So I know what you mean, it has a four speed and 4.10 Rear but it weighs 5000lbs. I too would use a single plane on a perf. engine, there really is no other way to make "serious" power that pulls hard "upstairs". Oh, thats in the dead of winter too!

by **Eddie** » 24 Feb 2007 10:59

Buttshot!