Model A Engine and Dual Carbs

[Railcarmover]

Model A trans bolts up to the clutch housing on the Cletrac HG..gives you enough reduction to doze with it..

[wingski]

I love the pictures of the downdraft carbs. Is that car of yours running? If not, get that thing running perfectly with the original Zenith or whatever before even thinking about dual carbs. I don’t want you to have to go through all the crap that I did trying to get it running with dual carbs. I’m very serious about this because if you don’t know that that engine runs perfect on one carb, you’ll be second-guessing yourself constantly about what is going on with the dual carbs.

And, for your sake and your cars, try to have another set of eyes available when setting up those dual carbs. Car fires are no fun at all.

Mike

[Ray in La Mesa]

I have a '28 roadster pickup with John Deere yellow wheels & Brumfield 7:1 head. Those and the twin "B" side by side carb updrafts on my home made stock A intake with an exhaust elbow braised on gives it about 25% more power, with the same milage, using stock jets(each carb thinks it's the only one there).

[Railcarmover]

This handy little device takes all the guesswork out of tuning dual carbs..or you can do it old school with a straw to your ear and listen to the air rushing into the carb...some guys swear by that. I've tuned 4 cylinder engines where one carb is dedicated to two cylinders, way more sensitive than the model A common intake runner most manifolds have. Once you've tuned them where they work correctly you'll never go back..Proper planning prevents piss poor performance, big old Strombergs are sexy but way too big for the application..Dick Steinkamp hits it with the 150cfm, carbs that flow higher than what the engine can handle will give you trouble..I've found going under the total flow rate gives better driveability and a better burn.

[PC/SR]

Railcar's "flow meter" is great for getting carb balance, but there is more to tuning than getting the air flow equal. Usually using bigger dual throat carbs are going to result in a bit gulp of air and a lean mixture when you stomp on it with some coughing and spitting, and it takes trial and error to eliminate that. (See Dodge, #38) Nothing wrong with the carbs, they are just not right for the application.
The three main variables are idle adjustment, main jet size and float level, and throw in the accelerator pump adjustment just to add to the problem because the kits usually have a different length pump shaft than stock on the Holleys (not a problem on the Stoms.) Add in the Holley power valve on dual carb applications (you must use aftermarket valves for dual use) and it gets sort of tricky. Work on the power valve nozzles.
For ordinary street driving, use the Stromberg 81s or the Holley Model 92s(.875 venture) and things are pretty easy and good. If you want more, the Holley 94 and Strom 97 are fine but a bit more tricky to get right and not much different in performance from the 81's for most street applications.
For more HP, use the bigger Holley EB and EC series from the '54-56 OHV, or the big Strom 48 but as Railcar says, too big for street driving.

[Railcarmover]

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^^^^Amen^^^^ power valves and accelerator pumps on high flow rate carbs only add to the issue. Basically 200cuin can only handle so much fuel. Working within the engines flow rate makes life easy....but down jetting and tweaking a big carb and hitting it right is like tapping a prom queen....good shit when you nail it

[Bob Bidonde]

Throttle response will be better with a single 2V carburetor than dual 2V carburetors. My favorite setup was a single 94 on Burns intake manifold, a Mallory dual point centrifugal advance distributor, a performance grind camshaft and 6:1 head. Not only did this setup give much gas mileage than stock, but the engine ran efficiently between 2500 and 3000 rpm.

[Ronnie Lawson]

20170717_204237.jpg20170717_204256.jpg
I have a setup that I want to sell. PM me.

[Barry B./ Ma.]

My 29 coupe has a Mitchell overdrive, stock 3:78 rear, 5.5 Snyder head and touring cam and I run 55 to 60 with plenty of power running a stock single Zenith carb. If I was to run any faster I would need to look at the brakes, different wheels, steering and tires. It feels like it could run all day at that speed range but things get busy handling wise over 60 with stock suspension. Take things a step at a time.