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

I would love to see a drawing of the runners on this manifold.

 

I'll stop down either the end of this week or next week at lunch time.

 

I'll see if I can get a picture tonight and post it tommorrow for you.

 

I've heard some anectdotal evidence that many engines run better with 4x2 than 3x2 - perhaps Bruce has the thinking right - 3 is overcarbed, but 4 is just right!

 

Here are the pics of the Evans 4 carb intake, I don't know if you guys will be able to see but the runners are divided a bit.

 

The only Evans 4X2 intake I've ever seen besides yours is a picture in D. Batchlor's Dry Lakes Book. Great find!

Joe:

How much chop did you give the Tudor?

Tim

 

Obviously, it's hard to tell in the pics - almost looks like common plenums for each pair of carbs with balancing chamber in the middle....

 

Hey Tim the chop is 3". I tried getting pics of the inside of the intake more but they just wouldn't come out visible.

 

What would be a better carb then; 97,81, or maybe holley 94s? I have to imagine 48's are WAY too big, and from what i pick up from you guys 81's dont have the cfm to feed the motor on the top end. So what would work best?

 

Flatdog's the one with the road experience, but find out size of his engine...I'm guessing 94's would have problems with pulsing causing erratic behavior of enrichment valve, but that's a SWAG on my part.

 

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

Yup.

Over the years I have set up at least 40 Edelbrock 4 carb manifolds for flathead engines.
All of these engines but one were over 300 ci. It was a 286.
I used Stromberg 48's on all of them with straight linkage. About half of these engines were in street type rods. The others were in race cars. They all idled under 900 rpm. Various cams.
The 3 carb manifolds I tried seemed to be just right but the 4 carb definetly made more hp both on the dyno and in the seat of the pants. All were very drivable with no flat spots. I even tried Hilborn injection on the street on 2 engines. Worked fine but it did have a flat spot by design.
I could move the flat spot around to different rpm's but could not eliminate it.
One thing both 3 and 4 carbs share on big flathead engines, the throttle response is almost instantaneous.
I have injectors on my 324 ci flathead engine in my race car and they make 1/2 second lap time better than my 3 pot. I don't have a 4 right now.
Pete

 

Pete1:

Is this cam grinder Pete from WA? If so, cool!

Bruce L. was talking about cams & that how intake pulsing might also effect the way the 4X2 set-up works. Any thoughts on this & some cam numbers that would help this situation?

Thanks

 

Banjorear. Yup that's me. The snow is gone and it is back to raining.

Yes, Bruce is right, there are pulses in the intake system.
Usually the narrower the lobe seperation (more overlap)
there is, the more pulse. Early engines with long duration cams would show a lot of fuel siphoning from the top of the carbs at high speed even if they were shielded from the wind force. This was blowback from the pulses.
This can be alieviated some by making the intake runners longer, either below the butterflys or above (ram tubes).
The length of the runners can be adjusted so they will actually give some positive pressure ram in one rpm range.
The 2 cams I had the best success with when running a 4 pot were the Potvin 425 and the Offy #4. The Offy cam is a radius lifter type and was the inspiration for Isky to do the 404. The #4 has a slighty less rate of lift so it will turn more without exceeding the mechanical limits of the valve train. The hp output from the 2 cams was virtually the same.Both of these cams in a big engine will work great on the street.
Pete

 

I'm think altitude added below carbs would be better than ram tubes above.
Below, pulses might end and get yanked back the other way without too much happening, whereas if the go through and revese above carb extra fuel is added as pulses go through venturis...hard stuff to think through and harder yet to find out what's actually happening with a lot of invisible air movement, changing with RPM...
I think a non-existent tall 4, tall like an Offy super dual, might be nice...
And if that Evans shown is as it looks, two nearly separated 180 plenums at ends of engine--that would be yet another picture: two throats available to each port, and some smoothing effect from more cylinders pulling through each throat...

 

Damn, Bruce!

You just keep coming up with more to think about. How about this offer: I'll get it the manifold on the engine and I'll take off the windshield. You can hang/lay on the gas tank as we drive & you can do any test you'd like....

 

All the info your getting is just words..Put the setup together and run it, see what happens and adjust from there..
Short and simple..
Duane

 

Yeah...this post does get the tuner impulse going. I've got a 276...I think I know where I can ge an Edelbrock 4....have 81-97-LZ-48 Strombergs for graduated response, and some articles around covering some of the issues...
This is a really interesting new thought here.

 

And remember--these things are the reason NHRA reuired those tin shields over the carbs on all those dragsters! You can check your mixture visually as it goes out and back in!

 

No kidding? I always thought that was to provide the carbs with "dead" air flow over the carbs.

Learn something new everyday...

 

Most agree that carbs like dead air space better than local forward-facing scoops...but NHRA had a rule about covering the carbs in the books...I'm sure it was based on something dramatic and nasty. Rule was there in the early sixties/late fifties--don't know how old it was. Radical cams, carbs, timing problems, last minute pit thrashing screwing up details...bomb factory.

 

Yup - the reversion is often referred to as 'standoff'; on later model engine tests, it's always neat to see that an engine runs better (and makes more HP with the air cleaner on. One of the reasons has to do with fuel standoff containment; an engine tuned to a specific A/F ratio can run stupid lean without the air cleaner. I did an engine once for a guy who had a lot of earwax on this subject; I ended up rebuilding it the next year after he burned a piston.

The thread does indeed provoke thought; thanks for recommending it!

 

BTW, if anyone is looking for an Edelbrock 3 pot ready to bolt on (with 48's,fuel block and linkage),
let me know.
Pete

 

Hello...Your on the right track.Strombergs 81..97..48, all perform better with the choke attached..Bench testing has been done and proven..
Duane..
ps..Point is, don't modify a Stromberg...

 

Duane:

100% agree with that. Seems like they got it nailed pretty good when it comes to performance vs. simplicity.

 

...i feel half retarded right now. Anyway, anybody got any other tips or advise.

 

Never personally worked with 4X2 on flathead, even though I'm entitled to wear the T shirt saying "been there, done that, wore out the Tshirt". when it comes to flatheads, in the days when they were fighting to compete with the OHVs that were entering the dirt oval modified scene.
And at the Lakewood Park track in ATL, a 1 mi dirt oval, I watched Jack Smith put a flathead powered '34 coupe in victory circle against just about every engine you can imagine. I looked the car over as close as right beside it, close enough to see the throttle linkage and it was direct, not progressive. IMHO, progessive is good for 3-2s,2-4s,and 6-2s only. As almost always, I agree with Bruce as concerns utilizing balance passages and progressive linkage on a 2-2s or 4-2s and not having problems.
Dave

 

Just a thought, but if you're just using it on the street, and you just want the aesthetics of it, why not dummy up some of the carbs?

 

This setup is on my avatar coupe but ready for a change in looks
so will sell the complete SBC setup for $1,000.
Rebuilt large logo 97's, NOS eelco linkage, and fuel block.
PM me with any questions.

 

well struck, Strange Agent

 

Because most of the 4x2 intakes don't have equalizer passages/tubes and you'd have "dead" cylinders not receiving any fuel...