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Discussion Topic:
Rough idle and back fires out of exhaust.
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40 Coupe |
10-22-2019 @ 5:43 AM
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Senior
Posts: 1674
Joined: Oct 2009
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The typical float setting for a Stromberg is 11/32" down on the free end from the top of the bowl. The standard factory jets are: Model 40 or 48= 0.048" Mains and #63 power valve Model 97=0.045" Mains and #65 power valve. They should all be marked. The original Carb for the 34 was the Stromberg Model 40 which is nearly identical to the Model 48 used in 1935. By 36 Ford changed to the Model 97 for better fuel economy. Ford Strombergs used an all metal input valve needle some aftermarket needles have a Vitron tip which is not stable with alcohol fuel. Not a good idea to run more that 2-1/2# of fuel pressure it can cause input valve to leak and excessive fuel in the float bowl. If your above this level I suggest removing the electric pump and have your original pump rebuilt by Charlie Schwindler. Excessive fuel tends to wash oil film from valve stems and rings
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Maine |
11-03-2019 @ 2:54 PM
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Member
Posts: 8
Joined: Aug 2018
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At this time I believe I solved the problem by addressing the rich gas problem, rough running and backfiring at the exhaust. the combination of going through the carburetor, running Marvel Mystery oil in the fuel supply and then running the car on the open road at 50 mph and a total 15 miles. On the existing 97 Stromberg carburetor I installed new jets .044, emulsion tubes, a designated 97 model power jet, idle jets and idle screws, and the new Grose jet that allows higher inlet pressure. The accelerator pump looked new but I did replace the pump check valve. The existing main jets were marked .045 but one had orifice almost twice the size as the other. I also decided to install a new diaphragm in the pump as I had it on hand. So the 97 Carburetor is from a 1936, is there some way to identify the year of the engine? With winter weather on the horizon, I put the car away until spring. I learned a lot through this problem and appreciated all the suggestion I received. Next spring after some more road trips I'll check the spark plugs to see if the fuel mixture is ok. Thanks to all of you who gave me so much info.
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flathead4rd |
11-04-2019 @ 8:22 AM
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New Member
Posts: 169
Joined: Oct 2009
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Sounds like you have solved your problem. I just thought I would add my own experience with the same exact problem for future reference. After checking all the possible problems I could think of including resetting the adjustable lifter clearances and still having the backfire out of the tail pipe, I decided the only place left to look was at the plug wires. Sure enough, #1 plug wire was breaking down and causing a weak spark. It would fire just enough to almost go unnoticed. Replaced it and problem solved. A lot of hours spent on such a simple solution.
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Maine |
11-05-2019 @ 2:32 PM
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Member
Posts: 8
Joined: Aug 2018
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During the time the engine was being rebuilt I went through the distributer . replaced the rotor (key was worn resulted in some drive play), one bushing on driveshaft had play so it was replaced, reset points (looked good ) replaced inner and outer caps and the spark plug wires. When the problem developed I checked the spark at each plug and it appeared ok but I did have a new condenser so I replaced it and still had the problem. At one of the members suggestion, I checked the voltage at the coil and it was low at 2.4 volts, so since I had a new resister I replaced it and got 3.3 volts but no change in problem. Just so nice having a great teem from the members working with you to solve a problem. Thanks for your input.
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40 Coupe |
11-06-2019 @ 4:23 AM
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Senior
Posts: 1674
Joined: Oct 2009
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The 33-34 engine block does not have a breather passage on the front of the engine block. The breather came into use after 34. Look at the bottom of the engine at the front, RH side of the oil pan and see if the small triangle shaped breather is there or if the block above this area has the breather passage.
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sarahcecelia |
11-06-2019 @ 9:04 AM
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Senior
Posts: 1182
Joined: Mar 2013
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Back firing out the exhaust can be retarded timing. We used to do that as kids to make them backfire like that!
Regards, Steve Lee
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supereal |
11-14-2019 @ 12:16 PM
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Senior
Posts: 6819
Joined: Oct 2009
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Check the engine with a vacuum gauge. One possibility is that you have an exhaust restriction. This allows an engine to start and idle, then the vacuum drops as the car is run. It can be from a carbon filled muffler. If you tap the muffler with a hammer, and you get a dull thud, it is time to replace the muffler. I have seen them so filled that they were hard to lift! If you don't have a vacuum diagnosis chart, I can post one or email it if you leave a message in my box on the header of this site. The vacuum gauge is still a very valuable diagnosis tool, and we use it often at our shop.
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