I recently acquired a 40 Ford Tudor. I have some plans for suspension and cleaning up the rust on the body. It’s a pretty clean car. I’m relatively new to Flathead V8s even though I did have one in the past. Couple questions. - Will 2 Stromberg 81s be enough carb? I’ve never heard of anyone using them on a dual intake on a V8. I wonder if it’s just because they’re more expensive. I have them for a banger project that’s on hold until the 40 is going. If these will work, it’d save me buying two 97s. -I want to hook up the mechanical fuel pump and keep the electric one currently being used as a primer pump/backup. Advice on rebuild or purchase a new one? Guy I bought from says he rebuilt and it still didn’t function properly. Is it possible parts are mixed up/wrong pump? Best place to buy? -There’s a threaded hole on top of the intake I have. Any idea why someone would have done that? It’s larger than a 3/8 bolt, probably a pipe thread. I plan on plugging it.
The threaded hole is more than likely for a PCV setup. I’d advise instead of plugging it you set up a PCV system. Best thing for a flatty. Check your rubber feeder line coming from the steel gas line to the manual pump connection. I bought a new one and it was junk. The rubber was soft and sucked the line to a point I didn’t have enough fuel. 81’s??? Good info here. I’d sell them and replace with two rebuilt 97’s. https://stromberg-97.com/information/81-learn-more-about-less/
I think the threaded hole is for a fitting to connect the vacuum wipers. It's an odd place to put it, I'll admit, but I have a Navarro Universal dual manifold with one in just about the same place. Unless the engine in the car is modified, two 81's are probably the ideal choice for dual carbs. They will probably work best with a straight linkage. If you are going to try a progressive setup, the front carb is the primary on those types of manifolds. If you are having fuel pump problems, the best thing to do is send it to Charlie Schwendler in New York for a rebuild. It will come back working perfectly, rebuilt with alcohol resistant components.
Tubman is correct, you need manifold vacuum for both the wipers and the vacuum brake on the distributor...
You should be good with the two 81's on a stock engine. That hole you see between the carb mounts is a prefect location to get a vacuum reading. You can use this location for a number of reasons first the most important use to set the two carbs correctly. When you run two deuces both need to work as one this means at idle both carbs should flow the same amount of air. To get the carbs each flowing the same amount of air a Unisyn gauge is used. To get both carbs flowing the same amount of air your adjusting the linkage connecting both carbs. The correct linkage to use needs to have a left hand thread on one end and right hand thread on the other end that has the arms connecting to each carb's throttle shaft. Once the carbs are each flowing the same amount of air next the idle mixture screws need to be set. To set the idle mixture screws a vacuum gauge is used that's where that hole in the center top of the intake comes into use. Connect the vacuum gauge to that location you can now adjust each of the four idle screws so that the highest vacuum reading is seen on your gauge. When both carbs are adjusted as I wrote you will be set. Also as Petejoe wrote above this center hole is a good location for the line to a PCV valve and also if you have Vacuum wipers its a perfect source for those as well. Ronnieroadster
For fuel pump, contact then and now auto. They have good kits. No need to send off for extra $$$ rebuild. Make sure mating surfaces are flat. rebuilding fuel pumps is not rocket surgery.
As a kid my 59A powered Model A with 2- 81s needed more carburetor. Most posters suggesting 2-81's are ok, have not tried them.
I think you’re all set with Ron giving you how to set up the carbs! Bench test the fuel pump. If it pulls fuel on the bench you may have an incorrect length or worn out FP pushrod. Also could be a worn cam lobe causing low or no fuel pressure. If it’s a fairly fresh engine check the rear cam bearing to make sure it isn’t hammered in too far. That’s my 2.5 cents! Kick ass 40 you scored!
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