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1931 Buick carbureation/ignition problem


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Have rebuilt carburator, and fuel pump, all new ignition parts, has both mechanical and electric fuel pump capability, no air leaks. Engine idles perfect with no choke but will not accelerate or run at speed with out at least 1/3 choke. Opinions please. Thank you.

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One question that might be of help to others. What is the history. Is this a car just purchased, or redone, or have you had it some time and did it run fine before the work.

Sounds like typical updraft carburator. How is the heat exchanger between the exhaust and carburator? Does it function and how is the control set? I generally run, with about 10% choke on my '32 until the car is quite warm.

John

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Most 20s & early 30s cars require some choke until they are up to temperature. There are two jets in the Marvel carb. I suspect the high speed jet may have a crack in it or you could just have the float adjusted too low.

Inspect the jets for cracks and solder as needed. Then run a drill down the jet to make sure no solder remains to restrict flow.

If your cork float is original, replace it with a new cork float and seal it with Krazy Glue (it will not react to modern gasolines). Make sure the float is adjusted so the fuel level is just below the top of the jets.

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If after checking and resetting your float and looking at your high speed jet, the car still acts the same way you may want to drill out the high speed jet. Gert a set of numbered drill bits between 61 and 80. Use these bits and find the size hole that is there now. When you have sized the hole, try grabbing a drill bit two sizes larger and drill the nozzle out. Alcohol in modern gas like to be set a little richer than straight gas.

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Hi, purchased car last Nov. It is virtually orgininal 32 K verified miles. Been working on it through out the winter inbetween restoration of 1929 Model A PU. Heat riser was welded shut sometime in the past. No linkage. Carb was leaking badly and was quite dirty and gummed. No matter how warm it will not run without the choke at least 1/3.

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Something else to consider is the fuel iine. I wrestled with a similar problem when I bought my '31 Buick 8-57. The original carburetor and fuel pump were rebuilt, checked out, and fine-tuned, and I still had fuel supply problems. Come to find out that, although the total mileage on the car was only 25K, the original brass fuel line had acquired, over the years, a veneer that was enough to reduce fuel supply to the carburetor. The fuel line had to be replaced, (and the gas tank was also cleaned out and relined). Then, no more problems! (Restoration Supply has brass tubing.) Good luck!

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Suggest you clean out the carb very carefully, using compressed air to make sure all passages are open. If it was gummed up, chances are there are still passages plugged or restricted. Also make sure the flapper is free to move smoothly. I assume you still have the original Marvel updraft on this car.

I would not drill out any jets at this point, that is not a reversible process and replacement jets are hard to come by. Assume the car ran reasonably at one time, you just need to clear out the obstructions if there are any. That's what it sounds like to me. Note that turning the flapper screw inward will richen the mixture. My Marvel has a major needle valve on the bottom and I have found the high and low speed mixture to be very sensitive to this needle. I am not sure the 31 Marvel has the lower needle, but it it has one, I suggest you open it a quarter turn or more.

You could also have a vacuum leak, intake gaskets can fail just from sitting. Put a vacuum gauge on the manifold and check that out. Probe with an unlit propane torch to look for vacuum leaks, the engine will speed up if you find one.

Good luck, welcome to the mahvellous world of Marvel!

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