Hot Rods Are you running multiple carburetors?

I was running 4 Holley 94's. I really liked how it ran. Straight linkage, 3.5" PVs .051 jets. The only issue was they leaked. No matter what. Even when I went through them to seal em down , they seeped. It got everything DIRTY. Then I went to 4 Nicely rebuilt Strombergs. They ran good but still had a little (teeny amount) seeping. Those are now set aside for my Olds motor and I went with new strombergs to see if the hype was real. It IS. Holy jeez these things bolted on and I had it tuned at an idle in 15 min, for 4 carbs. Smoother throughout the range than the holleys, and definitely more pep. And they are clean. No leaks. Big fan!

 

Not only on cars. Even go carts and just stationary engines in general.

 

These are Speedway carbs and they worked fine. A Unisyn is a necessity

 

Two Edelbrock 500 AVS carbs with straight linkage, Weiand WCA 408 manifold on the 390 Cad in my '40... Great throttle response!

 

Here is a pretty cool setup I just got done building for this 8hp. Runs smooth

 

What’s it going in?

 

It’s gonna stay on the ‘73 bird manufacturing go-cart for now. Fun little cart to destroy the yard with.

 

Here's a little video update. Got the idle down where I like it.

 

Dual 750 dp's on the 351c in my coupe...they work very..very well.

I've ran stromberg 97's and holley 94's in multiple configurations on flatheads/y-blocks.. You couldn't pay me to run any of them on anything again.

 

Hello,

Our first introduction to multiple carburetors was when my brother purchased his first new car in late 1957. He wanted a dual quad 57 Chevy Bel Air, but when he read some chatter about a new body style, a new bigger motor for the following year, 1958, he decided to wait. By the time the new models rolled into the dealer’s showrooms, he was all for ordering the top of the line 348 c.i. motor. (the actual top of the line was the same 280hp motor, but with a higher compression ratio and a solid lifter cam. But, the wait time was almost a ½ year for this model)

The three carbs were relatively easy to maintain and keep running well. It usually used the center two barrel and only when we stomped on the gas pedal, did the other two outside carbs kick in for extra power. The only time necessary to adjust the carbs was during our high altitude driving trips up into the 6000-7000 foot elevation in the local mountains of So Cal.

At the time, our expert mechanic friend from L.A. told us to adjust for altitude or the motor would not run correctly. it would run, but would feel like it is being choked to death upon acceleration. Once adjusted, it ran great, had the horsepower it should have and was one of the fastest cars, due to the adjustments. But, one had to remember to readjust the carbs once we got back down the mountains in lower elevations, or it would not run well.

Our friend had a series of carbs on his old motor in the 1934 Ford 5 Window Coupe. He like the dual quads for daily street driving, but, opted for the 6 Strombergs when making his runs in the A/Gas class portion of the Gas Coupes/Sedan Class at Lion’s Dragstrip. The choice was good efficiency at the daily street level going to and from high school, to the afterschool job and then cruising around. But he(we) found out that the Strombergs, despite the difficulty in tuning, made the most horsepower and had the best times for drag racing.

When we started our 1940 Willys Coupe build for the street legal Gas Coupes/Sedans Classes. We found a 283 SBC long block with an Isky Cam and aluminum pistons sitting in a small speed shop a few miles from our house. The price was right as it was not complete. But, a counter away in the shop, they had all of the parts necessary to put together a powerful motor. The main thing other than the Chevy truck heads was the 6 Strombergs on an Edlebrock manifold for the SBC motor.

The owner of the shop had a dual quad SBC motor complete and sitting on an engine stand. He said this was a good set up for the street, but at the drags, the 6 Strombergs would definitely be better. He also told us the steps in tuning/adjusting those 6 Strombergs for the top efficiency, while racing. So, now with a captive audience, my brother and I listened to what he was saying and bought the separate parts for assembly back at our small backyard garage.

Jnaki

At first, it was difficult once we got the motor together and installed it in the modified engine compartment of the 1940 Willys. It took some time to get it right, but, it ran great after adjustments and that was the starting point of our street legal Willys Coupe with an 283 SBC motor powered by the 6 Strombergs.
similar set up with 6 Strombergs

By the time April 1960 rolled around, we got our hands on a new Isky Gilmer Belt Drive for a 671 supercharger. We started our complete rebuild of the 283 enlarged to a 292 with all blower spec speed parts, rods, new heads, valves, pistons, modified/balanced crank, etc. We wanted a two port Hilborn Injection System, but it was cost prohibitive. So, we stuck to the tried and true 6 Stromberg carburetors on top of the 671 blower.

It took more adjustments, but once completed, the 671 292 SBC motor plus the 6 Strombergs ran like a top and even for the weekend street driving we did prior to racing at Lions Dragstrip, or just driving over to our local speed shops for a show and tell... that was fun.
similar to our 292 c.i. SBC motor

 

What they said.
Another "side sucker" freak here, and I find it simple & accurate to do my balancing with a listening tube.

My daily ......


My HAMBster ......


My present project ......

 

Yes, but only on different vehicles.

 

In the past I have run a 3x1 setup on my 170 in a 1963 Comet, 2x4s on my 272 Y.
My avatar is outdated, I currently have 6 multiple carburetor setups
SBC: 3x2 Holley 94s
3x2 Rochesters
3x2 Strombergs
I6 Chevy 3x1 Rochesters
Holley/Carter pattern 2x2 Holley 94s
Oldsmobile 215 6x2 Holley 94s
I am restoring a Studebaker Dictator intake and carb
Most of the setups have linkage that can be setup straight or progressive, depends on the
the driver or the size of the engine.
Setup and tuning are the key.

 

Saw this last Saturday…

 

From what I have read many times on here, mainly from Bruce Lancaster , - if running centre as primary, which is what your photo shows, block off secondary’s with a blanking plate and get centre carb set up and running correctly, then add on the others, secondary’s balanced with each other.

some good stuff here if links work, albeit slightly different carbs to what you’re running with....
https://www.jalopyjournal.com/forum/threads/links-to-holley-94-technical-info.286574/[/USER]

 

Thanks Clem! I hadn't seen that info on the 94s. Will check it out when I get a moment.

 

From what I can gather, the main difference is vacuum operated power valve in Holley, verses mechanical power valve in strombergs.
And stormbergs alway seem to run slightly smaller jets for same application.

 

Anybody out there know if there is a good thread on the HAMB regarding rebuilding Rochester 2G’s?

thanks all

mike

 

I like the 2gs too. This is my set up going into my 32. But I am of the more carb more motor school of thought. If you have a motor set up to run on 650 cfm. Stick to it. Over carb and motor and it never will run quite right. Just my 2 cents.

 

Clem - in addition to the mechanical / vacuum thingy, the functioning of the economizer / power valves is totally different.

The Stromberg valve has passages from the valve to the main discharge nozzles, so fuel from the power valve augments the fuel entering the discharge from the main metering jets. If the valve fails, the engine will run rich, but no fuel will flow when the engine is switched off.

The Holley valve has a passage directly from the valve into the intake manifold. Thus, if the valve fails, the entire bowl is drained into the intake manifold, whether the engine is running or not. This is the carburetor which is responsible for the phrase "leaking down".

Jon

 

On my 32 I have 3 Rochesters with proper setup ie no idle screws in front and rear carbs. So it usually runs on the centre carb and rarely it gets to use all three. I had a problem at one point where the front and rear carbs pushed fuel out even though not used. Turns out I had too high fuel pressure. I was using a Holley regulator that was a 6+psi . You can buy the lower pressure diaphragm and swapped that over and adjusted to around 3psi and problem went away.

 

What do you make for power with that setup? I have a 390 stashed for future use and am trying to figure out what multi carb set up I want. Right now I’m stuck on either the Weiand like you have or the Edelbrock like Dreddybear has.

 

What does this set up make for power? I have a 390 stashed away for future use and am trying to figure out a multi carb set up. Right now I’m kind of stuck on either the Edelbrock like you have or the Weiand like warbird1 has.

 

Not yet 30 years like Jim, but the pair of 650 Holleys on my 6-71 have been there 25 years. Took me 3 trys to find the right shop to dial them in, but they have been happy on my RPU for almost all of the 25 years.

 

Just the old stock two four setup on 425 engine that came in 1965 Buick Riviera Gran Sports. Still has the switch pitch turbo 400 that was bolted to this engine by Buick... yep, never separated as far as I can tell.

 

A pair of 750 Quick Times.

 

One for the rocker box thread as well.

 

My first multi carb set up was dual AFB's on a 67 GTO, then a Ford 428 CJ with triple hollys off of a T-Bird. That was way back in the early 80s. The several 426 Hemi's that I have been messing with all have dual quads.
My current masterpiece of ludicrousness is an eight carb set up on my early Hemi powered 31 Plymouth. It works very well. So far I have run 137 in the quarter with it, and on the highway it will pull down 14 miles per gallon. I’ll share my experience here on the hamb for anybody who wants to build something similar.
The engine is a .060 over 392 with a 5/8 stroker, 13 1/2 to one compression, and a .700 lift cam with 300 something duration. The carburetors are the bigger sized Holly 94's, with the 1-1/16 inch venturi.
The intake is in Edelbrock X.3, one of 15 that Vic Edelbrock senior modified for 8 carburetors to dominate SK boat racing.
It took a bunch of fiddling to get this thing working right. It’s not particularly hard to do, it’s just time and effort, testing and correcting. Then repeat.
The four inner carbs are primary, the four outer carbs are secondary, with a progressive linkage that starts to pull in the outer four when the inner four surpass 1/2 throttle. The carburetors use aftermarket aluminum throttle bases. None of them have power valves. Power valves are not needed, and would make tuning extremely difficult, especially with the huge overlap cam and low vacuum at idle. The secondary carbs do not have idle circuits. They all have accelerator pumps. I also installed adjustable main jets. This is not completely necessary, but since I race this car as well as driving on the street, I want to have that adjustability. I keep tabs on the air fuel ratios with a pair of Innovate MTX A/F gauges in the cockpit.
The linkage is built mostly of 5/16” x .035 wall stainless steel tubing with 10 – 32 stainless threaded rod inserted within and sticking out each end of the tube, with jam nuts and spherical rod ends threaded onto each end.
I don't particularly care for the look of them, but I used braided AN lines anyway. NHRA safety rules limit the amount of rubber hose that can be used, and I wanted something that can very quickly and easily be disconnected, and that would not put excessive strain on the fragile inlet threads of the carb body, but yet would deliver sufficient flow at low pressure.

Some things that I have learned: it is imperative that there is a very solid stop at wide open throttle that prevents the pressure on the foot feed from transferring to the linkage. You can see the stop I built in the picture, it is the cross bar at the front with the lightening holes and the adjustment bolt protruding. I did not have this at first, and the problem was that when I would mash the gas really hard, the whole linkage was under pressure against the wide open throttle blades. Things in the linkage would slip. So let’s say the arm that transfers motion from the cross shaft to four of the carburetors slips on the cross shaft. When you let off the gas, those four carburetors don’t close all the way. Not good. So building a stop cures that problem.
With the four primary carburetors all tied solidly together via the linkage, turning the idle screw on one carburetor affects them all. So with all of the idle stop screws backed out, and the linkage disconnected from each carb, then you set the linkage length to precisely fit the position of the throttle arm on each carb. Then you can equally turn each idle stop screw until you get the idle speed that you desire. It can be verified with a synchronizer gauge.
The idle mixture screws all get turned in and gently seated, and then backed out equally to achieve the highest idle RPM, so they always remain the same.
Since the intake manifold was designed for a boat, the carburetors were on there backwards. That worked okay on the street, but not on the drag strip. The fuel would slosh away from the main jets upon launch, causing a lean bog in the motor. So I had to re-drill the bolt pattern and turn them around, and refashioned the linkage to accommodate. Then I discovered that upon hard launch, fuel would slosh from the bowls back to the vent opening at the top of the bowl, and into the venturi opening of the carburetor causing a rich condition. So I covered the vent holes with a piece of sheet metal, JB welded in, and also a small piece of brass tubing pointed forward to allow for ventilation, but not allowing fuel slosh into the vent. You can see that in one of the pictures.

That’s about it. I’m hoping to improve on my previous best at the upcoming drag week event.