Helping a friend with his Model A Hot Rod. Before we open up a can of worms, I am fully aware of the complexities of this. It is a stock engine with upgraded 12volt solid state ignition system, dual 97's mounted on an "Equalizer" manifold and a megaphone style open header. (all brand new stuff) Idles ok, but really snotty, when you try and give it gas. Did a compression test(all 65psi) and tried to set the timing where it ran the smoothest. He is only running on the front carb. The jetting is a mid level size(have yet to pull carbs apart) Attempted to totally block off other carb, from the gravity fed gas tank. So...question is, am I fighting a losing battle with these 97's?? and should I attempt to create some backpressure, by installing a baffle in the header?? I am fairly well schooled in all engine performance diagnostics, but no real experience with one of these. Will try and post some pictures off my phone.
I don't see a fuel pump or pressure regulator. Strombergs need about 1.5 to 1.75 psi to run properly. Too, is the gas tank full and is there any crud/crap in the tank. One other thing to check is the shut off valve inside the car.
No fuel pump, just gravity feed. Tried just running fuel line to front carb, no changes Blocked off the header, a Little bit and it seemed to be more responsive Was thinking of building an adjustable baffle for header Sent from my iPhone using The H.A.M.B. mobile app
Ran a Holley 94 on my banger powered pickup for a long time with few problems, gravity feed for a while then installed a fuel pump and regulator. The gravity feed worked until I tried to go up a long hill with a partial tank of gas and had to stop and wait for the carb to fill up. The rear carb will be drawing air unless it is blocked off which will cause it to lean out, even with the butterflies shut it draws air. A friend blocked the rear carb off with a sheet metal plate between the gasket and carb. I ran about 10 degrees of advance at idle and tuned the springs to have about 30 degrees total advance (different springs from Mallory), was running a header through a muffler. Don't think you will ever get the carbs right as long as the rear carb is open into the intake, will even effect settings at idle.
I have two friends here in MN that have tried and abandoned the Equalizer manifold; one with a Winfield flathead, and one with a Riley two-port. Both had issues getting the manifold to flow with both carbs, and one of them tried running just the front carb with poor results (like you're having). The fella with the Winfield flathead eventually milled the dams out of the inside of the manifold which made it work like a conventional dual intake. The guy with the Riley took off the Equalizer and went with a single Stromberg, which outperformed the dual carbs on the Equalizer manifold. The key is, he didn't make any other changes; no ignition, plug, or timing changes, no changes on the exhaust side. The intake manifold was clearly the issue. If you have access to another manifold, either a single or dual downdraft, I would recommend giving it a try. By the way, the Riley is now sporting dual Strombergs on a Burns manifold and runs like stink.
Restore gas supply to both carbs. Make sure choke is all the way open on both carbs. Then change the accelerator links on both carbs to the summer setting so the initial gas charge is not so rich when you accelerate. If you have vacuum wipers, temporarily cap off the port on the manifold supplying vacuum to the wipers. Fire it up and use a vacuum gauge while it idles and adjust the mixture idle screws on both carbs until you get highest vacuum reading (all four screws should be the same number of turns out at this point). Now with vacuum gauge still attached, adjust timing until highest reading on vacuum gauge. Clamp down distributor. Now see how it responds.
Header supplied more heat than you can imagine Thanks guys!!! Sent from my iPhone using The H.A.M.B. mobile app
Here is a story my father told me. He raced a track roadster at Soldiers Field in Chicago right after WW2. All the flathead powered cars were running dual carbs. Andy Granatelli thought they were running too fast for the track, he wanted to slow them down. So he made a new rule, only single carbs would be allowed. The next week end everybody showed up with stock 2 barrel manifolds with a single carb. And they set a new track record.
A few thoughts: (1) Know nothing about this manifold, so no comment on the manifold. (2) On all dual manifolds I have seen running one carb is ALWAYS worse than running both, due to average cylinder fill density. (3) Original carb on Ford A was updraft with a fuel inlet much lower than the location on the downdraft carbs. Gravity feed is going to be marginal at best, PLUS (4) The Stromberg was designed for a pressure fuel pump (Stromberg specified 3 psi at the carburetor) and the orifice on the fuel inlet valve is designed for this pressure. Running gravity feed, even with the fuel inlets at the same depth below the fuel tank as originally designed, would necessitate changing the stock fuel inlet orifices to a much larger diameter or one runs the probability of not keeping the bowl(s) full of fuel. (5) Two two-barrels is a lot of air on an otherwise stock Ford A engine. Jon.
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