2x4 using two different CFM carbs?

I'm contemplating putting a 2x4 setup on a SBC 327, using two edelbrock carbs. One is a 600 cfm the other a 500 cfm. Any major problems with having two dissimilar carbs in terms of cfm rating on there???


Thanks for your 2 cent

 

I have progressive linkage on mine...it's the same thing as having two different sized carbs...seems to work fine.

 

A rat rod would have mix matched carbs. Some one who cares about building the car right would get matched carbs.

 

really not good plus too much cfm, find anouther 500 at least, but still too much cfm

 

yeah, plus getting by with what is in front of you isnt traditional.
(edit: evidently I didnt convey enough sarcasm in this statement cause people are misreading)



if squirrel says it works fine, I think that is almost a good enough answer for anything, in almost any case. Really. (this isnt sarcasm)

 

The real question is gonna be which manifold. Single or dual plane? common plenum?

That'll have more to do with it than anything. Some can be run progressive with no problems, some starve a few cylinders if run progressive. If it's one that doesn't like running progressive then you're gonna have a couple cylinders running a different mixture than the others. Not life threatening, but not optimal.

 

Thats what i think too.Some are single plane like,there it will be no prob.
But the ones for Chevys i've seen are dual plane design.With this type of intake i would'nt do that.Cylinders will run different A/F ratio..
But then,honestly:The only difference between 500+600 eddy ist that the 500s front booster has more meat to bring the cfm down.I've reworked a lot of them to 600 for the mustang crowd.No big deal,for cruising the setup is gonna run either way..

see ya,
Lincolnolli

 

don't listen to the negative comments here. Shit, I've been running a 500 and 600 combo like that on a tunnelram sittin on a damn HO 305. As long as you take your time tuning them and changing step up springs accordingly, you shouldn't have any trouble. I run both all the time without progressive linkage, responds like right now and still gets 16 to 17 mpg at 27or2800 rpms. Sure having 2 matched carbs would make it easier but there's NO reason you can't set 2 unmatched carbs to work together just fine. Go for it

 

Yes a common plenum, like I said what manifold is he using, that'll tell wether it'll make much of a difference.

 

nifty, now im going to jack this thread for me now.. seeing that its close to the
question i was going to ask anyways

i was planning on a dual 4 dual single manifold with 2 holly 500s and 2 strombergs in the middle of the 2 hollys on mini dual tunnel ram for the stroms, its going on a caddy 500 so it will handle the cfm.
anyone see any problems with this set up?
and yea, the linkage is going to be odd and wonderful.

 

Yupp!
Lincolnolli

 

Kinda depends on how hot the motor is too, 1100 combined CFM sounds a bit excessive.

 

I don't see no problem with this very interisting setup.As long as you have it idling from 1 or both Holleys.And alle the other carbs idle screws all the way in.
Thats what i did when customers run sixpacks with 3 cheap holley 2bbls.This way the engine does'nt get too much idle fuel.
I'd say its gonna run flawless,since the little Stromberg will see no vacuum(effect).The ,compared,huge Holleys will take over long before that.

Please,please post some pics then,OK?The Caddy 500 is my favorite OHV of all times.
This thing took me everywhere and back.The forever engine!!

Lincolnolli

 

will do, it will be a lots of steel shaping, and forge work, I'm not a fan of flat sheet metal manifolds. i also have a 425 caddy I'm trying to think of an interesting intake for, maybe an aircraft stromberg or quad turbos and fuel injection? who knows.

 

..what squirrel said.

To expand a bit, Not traitional? For me, I consider it's traditional to work with what I have. With the three monojets on my 'rod, I realize I'll never open it all the way up except on a drag strip. Before I do the drag scene, I'll need a roll cage, scatter shield etc. but that didn't prompt me not to put the carburetion with excessive potential for daily driving on anyhow.
..

 

If it's like the Edelbrock



it has all the right side barrels tied to half the cylinders, and the left side barrels tied to the other half. It'll run fine with a bit more airflow at the ftont or the back.

Also the Edelbrock carbs are a copy of the AFB and have an air valve in the secondaries, so the actual CFM at wide open throttle depends on air demand of the engine. It's likely the air valves will always stay closed.

 

Flow co-efficient differentials will determine if you can do this . Add the two cfm's together , divide by 3.456 . Multiply this figure by the air density at the altitude where you live . This gives you a multiple turbulence flow graphic . Multiply this number by your boot size . If it is 362 or over it won't work .

 

That is the exact manifold I'm contemplated using. Well.... that and a couple Offy cross ram adapters.

 

Mopar six packs run 500s on the ends with a 350 center 1350 total Mild 340 ci , 440 1355 cfm .0pen intake with vacume pods on the ends .c

 

I want to try that type of dual carb manifold on my BBF. But Run a pair of dellorto 45s. I know they make a 4 Weber/Dellorto set up, but I'd like to run 2. Make my own adapters, could be done, needs to be done. I just need the manifold. Maybe I should ask Santa.

 

You won't have any problems running the dual 500's on your big ol Caddy.
I run a pair of them on a 462" Buick with straight linkage.
Good throttle response off idle, real crisp.
Tip-in on the secondaries is very smooth as well.

I don't think you'd get much extra from the two 2 bbls . . . cept for the 'wow' factor.

If you're gonna do that, build a three 4 bbl intake.
Or if you want a real interesting intake, pop a Pinto Holley 2 bbl over each pair of intake ports.
Throttle response should be great considering the Pinto carb is for a 120 cid engine.

~~~~~~~~~~~~~~~~~~~~~~~~~~~

As for the mismatched carb question, a carbs a carb and the engine doesn't know whats up there.
As long as it runs ok, idles well, properly jetted etc.

I've been toying with the idea of putting my lean-jetted Holley on the dual quad intake in combination with a 500 or 750 cfm Carter up front.
The about 600 cfm Holley would be the primary carb and since the front cylinders run leaner than the rear, the whole deal may work out pretty well.

Kinda want to try a couple ideas I have concerning progressive linkage.

 

no such thing as too much cfm if tuned and set up correctly. I run 6x2 on a 10-1 pontiac motor works perfect. dont load up plugs exellent. do the math six small base rochester 2g's ! ! ! ! NOTE : i run a very hot ignition . spalding flamethrower with dual msd boxes. guys all tell me " you gonna wash the cylinders son "[ or] " hey man you are gonna get fuel dilusion in your oil " [ or] 'It wont work too much cfm for that stock pontiac motor". BULLSHIT ON ALL ACCOUNTS ! !

I also must note, Progressive eelco linkage with ALL idle circuits fully functional

 

a couple Offy cross ram adapters

Completely useless.

 

Is this the part where we ask you how come?

 

no such thing as too much cfm if tuned and set up correctly.
Unless the vacuum at WOT drops below about 1" - then the carb works very badly (Weber, Dell'Orto = exceptions), and finally below .5", when they stop working entirely.

do the math six small base rochester 2g's
At about 200 CFM each (depending on the venturi size) that's 1200 CFM total, but if it's an X6 manifold each bank of cylinders only gets 600 CFM.

" you gonna wash the cylinders son "[ or] " hey man you are gonna get fuel dilusion in your oil

Those are the people who think too much carburetor delivers too much fuel - that's backwards. Too much carburetor means too much air, and not enough fuel.

 

Is this the part where we ask you how come

I was hoping it was obvious. You don't get more water in the bucket by using a longer hose.
"Then why do they sell them?"
Because their purpose is the same as it ever was - you'll buy them.

 

Anouther thing, cylinders will not produce the same power through the rpm range because it is impossable to get the same cfm at a certain rpm

Holley even states that the BIGGEST problem people have is running too big of a carb, a venturi only works best at a certain rpm becuase of the vacumn needed, too little and gas acually pools up in the intake, guys like Barney Navarro have experimented with clear plastic manifolds to study that


As for the guy that mentioned oil dilusion, it is somewhat possable in some cases, when you step on it, that how much gas from accelorator pumps? especially on the 6x2 application mentioned before, and when they arent kicking it'll be having a hard time atomizing fuel

I know it looks Macho to run 2x4's on a car, but unless you're big cube/rpm it isnt the best setup. that said, i'm gunna try it on my damn near race 301, but power and overall drivablity on most motors you'd be better off with a single 4bbl

 

Ya can if you drain the hose.

Your last sentence is right on the money....

 

I'm running a pair of 600's with straight linkage, like was said the vaccume dictates the amount of flow, tune them and you'll be just fine.

 

my intake is a X-2 never heard of X-6. At W.O.T. i have zero vaccumm. the motor being nothing more than a big old air pump rellies on the pistons to suck, barometric outside pressure at that point takes over. talking all this magazine computor stuff is a never ending argument. this has been done my engine is living proof . guys will look right at it hear it run and continue to argue. I can set in traffic for three hours does not load up, run hot, plugs stay nice color. This takes carefull tuning carbs have to be correctly jetted, correctly re-built. If my compression was higher this set up would do nothing but get even better.

I guess it will remain me and C.W's secret maybee we should write a book patent it get rich. no reason to lie to anybody here. Reminds me of the myth you set a battery on concrete it will suck the charge outa it. dont knock a guys set up unles you have tryed it and failed first.