running 3x2 flathead pro/cons

49-53 flatty 0.30 over stock cam ect, thinking about a 3x2 setup, imput needed...for a every day driver..good the bad and the ugly

 

Most flattie gurus prefer 2-2's, easier to tune.

 

Know someone who is running a 3x2 with two of them capped with dummy carbs, only running on the center one. Is very happy with the setup.

 

3 is to much cfm for most flatties. you will be happier with 2 if you are doing it for the performance aspect.

 

2 is running all the time ,were3 just run the center one,i have 3x2all are running,but with progressive linkage richie...........

 

they are only 130 cfm each

 

save yourself a headache and go with 2x2 or a 4 barrel

 

I am running 3 Stromberg 97's on my late flathead......Eelco progressive linkage........runs on the center carb only most of the time.......the secondary carbs only come in when I mash it, which is not often.........very cool looking and reliable........

Choke on the center carb only......and smaller jetting and power valves in the end carbs.......works fine for me.....

CB

 

i run 3x2 with progressive linkage on a 50 merc and love it. on the next project im going to try 4x2...........why not

 

richie rebel..the 97s are 150 CFMs, some are higher..Your Flathead will run just fine with the 3x2 and progressive linkage..I wouldn't change jets or power valves and all three have the choke plates..Only the center one for choke operation..You could run Stromberg 81s, 135 CFMs..Lot of old hot rodders ran 97 primary and 81s as secondaries..
Duane.

 

so for a everyday driver, not a race car, what is the best combo ?

 

You'll get a dozen different answers to that...

...too subjective.

Virtually any setup can be tuned to run well on the street...

 

thats what i was afraid of... this sounds good so far,from another post, the 97s are 150 CFMs, some are higher..Your Flathead will run just fine with the 3x2 and progressive linkage..I wouldn't change jets or power valves and all three have the choke plates..Only the center one for choke operation..You could run Stromberg 81s, 135 CFMs..Lot of old hot rodders ran 97 primary and 81s as secondaries..

 

I ran 2 x 2 for a long time ran great and fairly economical. Put 3 97's on with straight linkage. It was like adding half another motor to it. The engine is a 3/8 x 3/8 with a good cam and electronic ignition. of course it's relieved ported and polished. Gave it enough extra power with that long arm in there that it busted the center main cap.

 

Huh, I have been thinking about running an 81 as a primary and 97s as secondaries (on a 215 Buick tho), would that be too far out of the realm of reason? Or is it that the 81 is so small that you wind up in the power circut of it (the primary) or into the secondaries too often?

Sorry for the hijack (if it is, it is on topic, sort of )

 

thanks, i was just looking for the best combo for everyday driving....

 

The advantage of the 81 is that you get into venturi-fed, hence properly metered, delivery earlier (at the cost of running out of capacity earlier)...I suspect that multi carb setups spend a surprising amount of time running on their off-idle circuit...look at the Ford discussion of this circuit in the Stromberg operation/overhaul instructions!
And do look up the 4-carb discussions; these seem to be functionally IR systems with most manifolds, meaning that a 4 might be too little carburetion for a flathead on which the triple is too much...carbs are subversive creatures. IR setup 350 nChevies happily use 2400 CFM setups on the street...think about that.

 

okay duane thanks i do run 97s didn't know they were 150cfm,my motor is 286 cu in all three chokes are wire open no problems at all,and ernie your right,its all about what your taste is,2carbs are opening all the time,more gas..richie........

 

Distilled down to the simplest terms...

Anyone running a stock or slightly modified engine (just a cam, just heads or something like that) will see improvement going to a 2x2 set up. With this, run straight linkage.

You would also see a slight improvement (maybe) with a 3x2 set up, but only with progressive linkage (either a single main carb with outer 2 kicking in, or 2 main carbs with single inner kicking in)

Remember, if you're using a vacuum only distributor (stock on 49-53) you will have to change that to run multiple carbs. This is another expense to consider.

In my opinion, run the 2x2 set up. The very slight (if any really) gain on a stock engine going to a 3x2 set up is not worth the added cost of a third carb and the cost of progressive linkage. Plus, on a stock engine, there's a real possibility that performance will DECRESS with a 3x2 set up at full throttle. A stocker can't really use 450 CFM of carburetion even at WOT.

Just my 2 cents...

Matt

 

I watched a dyno pull with a 3x2 & straight linkage on a bone stock 239 - it did fine & made more HP than stock or 2x2 (these were back to back tests single 97, 2x2, & 3x2). Power was only marginally better than 2x2 & AFR was on the rich side at WOT suggesting street use might load up plugs w/o working the jets/PVs. It did rev find - no bogs or anything - surprised the hell out of me.

Didn't watch, but same dyno, different engine - strong 276 - 3x2 made significantly more power than 2x2. During these pulls, a couple different 2x2 intake were tried - Offy Super made better power than Thickstun.

But you don't drive a dyno, nor do you drive around at WOT all the time. Streetability & driveability aren't always apparent when comparing peak HP numbers on dynos. Carb tuning & ignition timing will be critical when you're running lots of carbs in order to get the driveability aspect down.

 

I don't have a damn thing that runs to play with right now...but I suspect a lot of driveability and response answers are hidden in the off-idle circuit. A multi carb flathead is not even USING its main jets most of the time, I suspect. That idle jet might very well bear some attention in developing street response. Also, since engines naturally must spend most of their time at part throtte, vac advance is almost certainly much more important to power and response than generally assumed. Typical dyno runs can't even look at this...
Ron on Fordbarn has been looking into this, generally using SBC distributors to get easily tunable advance systems.
Yunick once opined that the reason racecars oft have plug fouling, especially under caution/slow running conditions, is their traditionl lack of proper advance at part throttle.

 

For a nearly stock engine, try a Merc four bolt carb and manifold. A bit bigger than stock, but not overwhelming. Look into a hot ignition too.

 

what about 3 94s

 

well decided on three 94s maybe 91-99 any sujestions...

 

What made you decide to use 94..cost?????
Duane..

 

Run two on a Thickstun PM7 - looks kool as hell, is cheaper than 3 97s and runs great!

But if ya gotts to have 3x97s have a go and see if u like ot with a progressive linkage. Hell theyre only carbs....easy to swap out !!

Rat

 

A bit off topic, but a my pal asked if he can use any flathead 3X2 intake on his -53 Merc (CM) engine. I assemled 2x2 Offy Ford flathead intake to similar mill years ago and I think i had to bore and grind intake quite a lot. So, is there any 3x2 special intake to Merc?

Thanks, Ari

 

i'm gonna throw a question in..

2x2 intake with 2 94's and electronic distributor with both vaccuum and mech. advance......will it work?

 

iam just getting ideas...but cost could play a part, i love the look of strombergs, way better....

 

so if i am going with 94, witch ones do i look for....