How realistic is it to run 4X2's on "street" flathead?

I want to talk to reality here & not bench racing lore....

How realistic is it to run 4X2's (using 97's not the more widely used 81's on a 4X2) intake on a light roadster?

That set-up just looks so bad *** that I'm half tempted to just go for it.

 

If you've got the parts...very realistic. Why wouldn't it be?

 

I'm fortunate (or lucky) enough to have all the stuff. I've always read that 3X2's on the street flathead is too much. With that logic, I always ***umed that 4X2's would be way over kill.

I was fortunate to pick up a nice Edelbrock 4X2 that I was going to run on my FED. I'm going to use 3X2's on that instead of the 4X2 set-up. So I have the intake hanging on the wall & would like to use it.

 

Very, I ran this setup for a year . 81 and 97 at difference times

 

I still don't see how you could get anywhere near decent performance out of 600cfm in a 239ci motor with one of the worst volumetric efficiencies you could imagine. considering 600cfm is good for a decently built 300+ cube overhead......

 

Flatdog:

Did you have any problems running it with 97's? I heard your 4X2 set-up @ Magungie and before you came over the hill to enter the show, I thought your car had a souped up SBC before I was presently surprised to see it was flathead. That motor sounded and was bad ***!

Remember: this is really going to be a street car.

 

I'm putting 4x2's (97's) on my sedan, I am going to try it without progressive linkage at first and see how I can tune it, motor is 284 cubes, ported and relieved with a larger intake valve. It will still be a while down the road until it's finished but I feel confident I can make it work properly. If it doesn't work with straight linkage then I will try the progressive and adjust accordingly. I'm going to use those oval shaped air cleaners on this as well.

 

you'll never get it to idle right with 4 idle circuits, and your standard street RPM range will have no torque. hope you got big gears in your rear end to keep that thing wound up to where it will run right

 

This might be a somewhat different case than the 3-2's...these 4 carb stups are barely manifolds, generally--they have a straight shot from a carb barrel to port, and small connecting p***ages only. If they act more like an independent runner setup than like a manifold exposing several throats to each intake pulse, considerably more CFM would be fine. Problems in mixture caused by reverse pulses when engine is off the cam might be worse...
I've never been near one of things, but I do believe this must be viewed differently than just a triple with another set of holes.

 

Bruce:

You are correct on your observation. The equalizing ports (if you want to call then that) seem smaller than a regular manifold 2X2 or 3X2 manifold.

 

I perfered the 97s,Funny story leaveing Rhinebeck about 6 ,7 years ago my buddie a couplle cars behine mein traffic at the fair ground heard two guys argueing about my car.One guy said it had to be a chevy because no flatmotor could sound like that.

 

It can be done. HAMBer john Ford Man built this Coupe....it was about the baddest thing on four wheels..........I hate the changes that were made to it after he sold it though. It ran four '97's and was a great running car.

 

Thnaks guys. I'll really leaning towards doing it. What the hell, it's only a chunk of metal if it blows up, right?

 

they have an article in this months Ol' Skool RODZ mag about this question. check it out its a lot of info that will help you out for sure

 

Not to sound too out of it & knowing that mags are months ahead, which month's issue are we talking about? Thanks. I'd like to check it out.

 

You'll have a lot easier time setting it up with straight linkage. Just be sure that you have all the ****erflies closed and all of the throttle arms off the carbs are parallel with each other. You would have 600 cfm available but it wont pull in more air than it can use. you just have to get it jetted properly, I run 3 97's straight and I beleive they're jetted 43 or 45 , can't remember. It ran like a son of a gun on a 296 with a good cam. I'm pretty sure you can make it work. Good luck STafford

 

Thanks. Yeah, I was planning on running it straight. I wasn't planning on going as big as your engine, maybe 286. That may hurt the bottom end as well.

Seems like it will get all the air/fuel it would need. What cam did you run in your set up? I have a couple to choose from & just sent two cores out to Clay Smith for regrinds.

 

Hello...Both of these setups, that I built ran good..The one with the adaptors ran a little better because of the progressive linkage..Feedback from the buyers
DO IT
Duane

 

This one belong to a HAMBer and runs real good, there's a video of it running posted here (Woodward Dream Cruise) but I couldn't find it withe the search function..

CC

 

Here are some purely theoretical thoughts on this: Need for carburetor capacity goes UP from 360 degree manifold to 180 degree manifold to individual runner manifold. The flathead 4 carbs typically are not true IR designs, as there are substantial connecting openings, but I would suspect they behave generally as IR's--they are not at all like the setups used in normal 180 degree FH manifolds. The IR design is also compromised a bit in the carbs, since Strombergs have a bit of common space between barrels, unlike Webers and such designed for IR use.
On a pure IR setup, each cylinder making an intake stroke sees one carb barrel, period. On a 180 manifold, each intake valve has full access to half the total number of carb barrels and some extra flow probably from the others.
This means each barrel can be tuned for its cylinder without having to cope with manifold problems, it means you examine CFM one barrel at a time, AND it means the pulsing that's going on in the flow at less than high volume/cam tining at sweet spot conditions can drastically mess up mixture, since it is not damped by overall flow pattern through manifold. On a short manifold like these, there might well be air moving in/out/in at some times at low R's with rough cam. Venturis work pretty well in both directions, so this can be a real problem, as well as motivating NHRA to mandate carb covers long ago! Anyway, I think these things are closer to being IR's than manifolds, focusing on the normal aftermarket fours, not log or adaptor types, and CFM and tuning considerations will be completely different than a 3X2. And I don't think they will be happy with progressive linkage, either.

 

Make sure you buy that Edlebrock carb sync tool. Just my $.02

 

Bruce:

Wow, that is some pretty heavy thinking in the logic department. Makes sense & it will be interesting to see how it plays out. I agree with your IR mapping & do not think progressive linkage would suite this application well without starving some of the cylinders as it is designed.

Thanks for taking the time to post

 

Here's one way to look at IR, keeping in mind that this isn't a true IR entirely and that there are LOTS of considerations and oddities in one barrel feeding one hole...

Look at a stock flathead with a 97: split manifold allows little crossover, so each barrel is feeding four cylinders...when an intake opens, one cylinder is drawing from one barrel. Most would say this engine is undercarbed and would go faster with more...
Now throw a triple on the same engine: Again, 180 degree split manifold, when one intake opens, one cylinder sees three barrels of carb...many would suspect this engine is over carbed if close to stock.
Put on the 4 carb, and view it as an IR...now one cylinder opens, it draws from one barrel again...with unknown amount drawn from those connecting p***ages.

Shocking thought: Could it be that 3 carbs is too many, so putting on four will be about right???

I dunno. Never tried any of this. But this is a different animal from other flathead manifolds, not just another multiplier...there are interesting Vizard articles on putting an IR type setup on a SBC Chevy using Weber clone type carbs...for a SHOP TRUCK! The purpose, full achieved, was not for racing but to give this lump a diesel torque curve without the expense of a diesel engine!
Another random thought: The natural habitat of the flathead 4 carb manifold useta was on fuel burning race engines. I think part of its purpose was to simply increase the number of holes for fuel as much as it was for air! Nitro carries along its own oxygenation, and the quan***ies needed are hard to flow through carbs originally made for gas, even on the ultra simple Stromberg with dump tubes discarded!

Now, whereinhell is Flatdog?? He's actually run one on street and track...

 

This is not true. Bruce (as usual) hit the proverbial nail on the head. If you study these intakes closely, you'll find that they are much closer to an individual runner intake than a plenum type. They are two completely different creatures to tune and CFM requirements are different.

Now, that being said, not all 4x2 Flathead intakes are the same. There are some out there that are true independent runners where each carb feeds 2 ports and there is zero balancing between cylinders. Duane has a picture of one in his post above. These are very difficult to get tuned and a real ****** to make idle at less than 1,000 rpm or even higher. They have almost no bottom end but work well at w.o.t.

The beauty of the 4x2 from Edelebrock, Weiand and Grancor (the 3 types I have currently in the shop) is that they for the most part act like and independent runner set-up, but still have just enough balancing between cylinders that it makes it much easier to run than most guys think. The best of both worlds if you will.

I hope we have helped more than confused you. LOL One other thing to consider is that progressive linkage might not be such a good idea on these intakes because of their design. You may end up with some cylinders running lean at cruising speeds. Also, progressive linkage is usually not necessary on such a light vehicle. Heavy cars with lots of carbs will "bog down" just off idle if the intake charge velocity is not kept high enough. In your case, the weight is not an issue and the load not very high on the engine and it will pretty much take whatever you give it.

Matt

 

Progressive linkage will not work right on a Weind man. I tried it.I given some thought to what Bruce said, it makes a lot of sence,My car seemed to run out of air flow with the 81s,deffinlly pulled better up stair with 97s. Car proformed just as well with 3 97s on Navarro man.

 

Wow, that is some pretty heavy thinking in the logic department. Makes sense & it will be interesting to see how it plays out. I agree with your IR mapping & do not think progressive linkage wouldn't suite this application well without starving some of the cylinders as it is designed.

Matt:

I'm in agreement with everyone regarding the progressive linkage.

Flatdog:

I'll be reaching out to you soon. Thanks again. Interesting that the 3X2 Navarro ran the same. I've always read that the Navarro 3X2 ran real well. I have one of his earlier 2X2 intakes.

 

What about this intake where the runners looked siamesed together, this is the one I have in mind.

 

Is that an Evans?

 

Yes I have the same one, this is just a picture on the computer.

 

What do the actual p***ages look like in arrangement and in size of longitudinal p***ages?
I have Evans 2 and 3 manifolds, and they have that molded lump look too, but insides are pretty normal 180 degree flathead looking.