Crazy Multiple Induction Question!!!!

M

MandarinaRacing

Famous Member
OK I know I have asked this before.....but I'm a stubborn SOB......I'm still contenplating the idea of multiple carbs in the future....WEBER DCOE's or IDF's would kick ass, but the cost is prohibitive. So are there any other 2BBL carbs (3x2BBL) that I can use that are cheap and deliver as good performance as a single 350 or 500 Holley. I was thinking of three Datsun carbs, but the only thing is I don't know anything about them.....how 'bout some suggestions......XECUTE??????

Alex
 
Triple Rochester 2GC carbs would work. They used to be a kit to install them on VW beetle engines. I think triple Autolite 2bbls would work too. When you go to an individual runner setup, the carb cfm rules change.
 
I have wondered about the Varajet 2-barrel carbs. They are common here and cheap enough.
 
You can go with .98 venturi Autolite 2100s. They flowed only about 190 CFM, so if you had 3 of them, that would kick arse on a 200.

I'm not sure if you are considering this, but with 3x2V, with an inline 6, you can set up so each barrel of the carb feeds one cylinder. Just put a plenum divider in and divide each carb. Basically, it was act as 6 1Vs.

Slade
 
the Varajet 2-barrel carbs are superb. They are half a QuadraJet, but French made, and just as hard to tune. Same issues as all the Qjet...great if you have 16 metering pins and hangers and jets, and a Tech Test3 dyno, but way beyound us mere mortals.

I've looked at just running a sideways 350 cfm #2300 Holley to feed the log 60% of the time, and then some really rare #2300 Holleys used on the front and back banks of the 1968 to 1970 Mopar 340 Six Packs. These were vacuum operated from a 4150/4160-style vac sec dashpot, linked to the throttle. Vacum tripped them in, with an overide from the throttle lever over 2/3rds throttle. Mount these carbs on the outside of the stock 350 Holley 2bbl, and you can tune the engine to use the ~ 155 hp capability these carbs have. When the vaccum signal from the main ventur drops, the secondaries open the outer throttles.

This is sort of like a six-bbl carb running like a 4-bbl.

I'd estimate a single #2300 350 with two 56 jets for about 85 hp total if the two outer carbs weren't working. Set the power valve to 6.5"Hg. The use two #2300 350's with no choke horn, and both power valves blocked off each. Then jet to twin 45 jets each. These yield about 57 hp each, for about 200 horsies total. As long as all else is cammed and valved , compressed, and geared to hack the pace. Even that may be to tame a jeeting for this set up. Perhaps an evil 300 hp fire-breathing engine is hiding under this kind of carb set up. Then you'd need 66 mains on the centre carb, and 56's on the outers, by my calcs.

The advantage is the set up runs lean, on the centre carb, most of the time, but under wide open throttle, you've got gas b-a-d.


That's 6.65 sq in of carb area wide open throttle, the same as a #4011-800 cfm 4-bbl carb full tilt, but only a little 350 cfm car (in fact, a 250 cfm carb) most of the time.

What would be really cool is to take the operative choke of the centre carb, and use #6425 650 cfm Holley 2-BBL ram tubes, which are like #4500 Dominator tubes. Shove six of them mean weeds out the bonnet, and see the road ahead clear like the way before the Running of the Bulls!

Whamo, make shift Webers, at a third the price.

If it works on an eight, it works on a six!
 
XE wrote:
I've looked at just running a sideways 350 cfm #2300 Holley to feed the log 60% of the time, and then some really rare #2300 Holleys used on the front and back banks of the 1968 to 1970 Mopar 340 Six Packs
Click to expand...

You mean like these????

6packCarb.jpg


These 3 carbs would total 1350 cfm, how " cammed and valved , compressed, and geared to hack the pace " are we talking about here???? It does sound like a great idea!

I think the Autolite 2100 would be a better option, but would have to block the intake to seapate the carbs right?

soooo....what would it be?????

3 of these
2100%20ls%20s_20021028215703_t.jpg


or......

3 of these

6packCarb.jpg


or....

TRHEE OF THESE !!!!!!!! :twisted:

s0-80600.jpg


Alex
 
I was just surfing evil-bay and there are a lot of Solex, Mikuni, Dellorto, and webers out there pretty cheap. There was one set of triple solex 40mm sidedrafts (same as 40DCOE) for $169.....Many more sets for uner $200.
 
THX Jack, yeah I've seen those, the only thing that kinda bothers me is that they're DCOM's and not DCOE's supposedly there no good.....anyway, been looking at Mikunis and Kehins lately.....it's been a really slow day here at the office so the mind wanders..... :wink:

bye

Alex
 
Motorcycle carbs wok well. 4 750 Honda carbs work good the largest ones have accelerator pumps in them. Ultimite would be the Ed Vac now Edelbrock Quick Silver series. The Quick Silvers are cool constant velosity single metering system automaticly altitude cominsated. Easly mounted to log manifold by braseing tubs with flanges 2, 4 or 6 of them.
 
Over the last 9 months I've been here, I've come to the conclusion a wild six needs to be mild and wild. Just cruisin', it has to run like a Rochest Qjet, really lean and with a high air speed. Something like a stock log In-liner, in fact. Then, under load, it needs to have a well distributed air/fiel mix, with all cylinders getting a hit of bubbly.

Weber DCOE's do this easily, they are supper adjustable, but are needing a cut off log with a custom or Lynx intake adaptor. And the have to fit the spring towers.

:idea: No. 1 is the "vaccum tertiary" triple 2100 or 2300 (not the split 4500's, unless you plan on 1300 hp normally aspirated :twisted: ). These are likely to j-u-s-t fit if you are carefull with a tubing set of brace bars. The issue for me is making the jetting and linkages work. The vaccumm operation is a no brainer. The linkage is a lot more complex. But it has all the features we'd like...lean off the gas cruising, full bore on the gas.

:idea: No. 2 is the idea of running them all together. Just like a set of IDA's or IDF's. There is a constant air velocity if the carbs are turned in to mate up with the individual ports. The two center ports are not spaced the same, so it spoils a complete independant runner intke system, but I'm certain it can be made to work. The Holley is the pick, all ciruits are fully adjustable. What is the difference bewteen triple IDF 44 running 35 mm chokes and a set of 500 cfm Holleys ruuning 42.8 mm throttles and 35 mm chokes? It's all in the progressive jetting. I guess the Webers atomise better than Holleys, but there is complete adjustability at a fraction of the cost with them.

I'd say a full 200 hp engine may need six 49 jets to discharge the 1100 cc/sec needed.

Lots to think about!
 
Well I found an article on the rebuilding of a six-pack carburetor set up. The inboard carb it's just like a regular 2300 2BBL....the outboard carbs are a little different. They have (as XE stated) a vacuum operated diaphragm that opens the blades. These carbs DO NOT have idle mixture screws, an accelerator pump, jets, power valve or a choke assembly. They are either "on" or "off" . Apparently this system tends to be unreliable (wouldn't imagine why?) according to another article. This set up would elimanate the need for a crazy progressive linkage. The only problem now would be locating these carbs, apparently no one does a complete re-build kit for the outboards that includes the vacuum diaphragm. I'm very much into this idea, I'm still in the research mode, since $$$ is scarce I always start way ahead on things I wanna do.
Here's the article link....
http://wwnboa.org/h2300r.htm

Alex
 
Alex,

Why not try the same vacuum operated idea using 3 1 Bbl carbs?? The center is operated with regular linkage, but the outboard 2 are operated with the vacuum secondary diaghrams off a holley 4 bbl??

You can get different size secondary springs to dial in the appropriate time for the secondarys (outboard carbs) to open up.

That was always a idea I had in the back of my mind :wink:

Doug
 
I've already thought of a crazy set up like that but with a twist....one 2bbl in the center and two 1bbl carbs in either end. :shock:
I remember asking a question a while back about wich set up was better ( two 1bbl, one 2bbl, three 1bbl) are answers were very subjective. For the most part I think a multi carb set up is mostly for show, but on the other hand the Pontiac guys and Mopar guys claim that the rush in acceleration when the two outboards kick in is impressive. I'm in no means (time or money wise) in a hurry to do this. It's just that a hi-po inline does deserve to be unique.

Alex
 
Absolutely. The transfer slot is just a simple device that triggers secondary cut-in. It just has to pick up air speed differential between both the secondaries and the primaries.

It's just a means of sizing the tubes to duplicate the vac sec set up. The Mopar set-up is my pick. It's brainessly simple. But I haven't sussed out how it works exactly, yet.... :duh: :stick:
 
Vood you like to consume the Holley Grail for Mo'Powa?

Bloody slant guys. They are at the cutting edge and we are worried about the morals and ethics of shoving a single 500 on a 200 cuber... engine :wink:

Just a note on some mistakes I've made in my thinking too.

Error One: Triple Holley 500's would be okay for a mild 250 or a wild 200 . As a vaccuum tertiary set up, like the 340-6 Pack, they would need to be jetted the same for each cylinder. I made a mistake, wasn't thinking. When you delay the action of the outer carbs mechanically or by vaccum, they must be jetted a similar amount so that the deliver equal amounts of fuel at wide open throttle. MandarinaRacing, your on the right track.

Error Two: If you were able to build a screameer 250, then those split carbs you posted, the 51mm throttle, 43 mm, 1.6875" venturi #4500 Dominators could work very well on an engine reving to 6500 rpm tops. The Aussie 265 Hemi Chargers used 45 mm Webers with 40 mm venturis with a power band to 5500 rpm, but it could rev to 6500 at a pinch.

Checkthis link here for carby specs

38|#4500-|1050|4-bbl-|2.000-|1.6875--|4.4731|18.5-|2.000--|1.6875--|8.946--|~282ft/sec|328|656|
 
i got a better idea direct port electronic fuel injection :P :P

and if you really must persist with them nasty carbies then i'd go for six (yes thats 6) 38mm (or there abouts) motorcycle carbs it'd be the ducks nuts!!

cheers.joe.
 
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