| istrum | -- 10-12-2023 @ 2:28 PM |
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Hello from Little Rhody R.I. My '46 flatty has gotten very meticulous ever since I parked a month ago. She's backfiring out the tailpipe on acceleration. Idles fine, new carb and electronic ignition. I'm suspicious about the power pump in the rebuilt carb. plugs are blackened from idling for too long. Unfortunately I don't have a timing light.. I'd appreciate any help from from you guys! Thanks, Mike Jackson
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| carcrazy | -- 10-12-2023 @ 8:47 PM |
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Backfiring out the exhaust pipe is most often caused by ignition system problems where the spark is not sufficient to maintain complete combustion in the cylinder. I would throughly check out the ignition system first. Another cause of exhaust system backfires could be exhaust valves that are leaking which allows fuel/air mixture to finish combustion in the muffler.
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| istrum | -- 10-13-2023 @ 4:37 AM |
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Thanks Carcrazy, I will start with the ignition system changing the plugs and check timing. I'll work my way from there. I did pull a plug yesterday and it was pretty fouled up with carbon. when it was running it smelled rich w/ black smoke. Could it be the power valve in the carb or air fuel mixture? It's a rebuilt Holley 94. I ordered a new power valved from Charlie Price anyway. Thanks again, Mike Thanks, Mike Jackson
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| carcrazy | -- 10-13-2023 @ 8:02 AM |
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It could be any of several things: Idle mixture screws out too far allowing excessively rich mixture Failed power valve leaking fuel past diaphragm or incorrectly made PV preventing gasket from sealing Wrong carburetor calibration for your engine Check the main metering jets (MMJs) to see if they are the correct size - somewhere around 48 or 50 should be a good starting place (if my memory serves) . If the mixture is still too rich as indicated by carbon fouled spark plugs (assuming the engine does not burn oil), go to leaner MMJs (lower number marking on jet) until you can get the engine to run properly. A vacuum gauge can give you a lot of information about the mechanical condition of your engine. A compression gauge reading of a cylinder that is lower than the others can indicate a leaking exhaust or intake valve. A timing light is essential to set the ignition spark advance.
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| istrum | -- 10-13-2023 @ 5:34 PM |
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Hello Carcrazy, Well, I replaced the plugs and tweeked the timing and she runs like a sewing machine as they say...except after idling for a few minutes the plugs are carboned up already! I turned the left side needle to close and backed it out, did the same to the right side needle, I turned both sides 1 1/2 turns but the engine didn't change at all. All I can think of is the carb is out of adjustment. I haven't done a compression test yet. Thx, Mike Thanks, Mike Jackson
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| sarahcecelia | -- 10-22-2023 @ 1:47 PM |
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You only need a timing light to check the advance timing when you rev the motor. You can set the initial timing staticly. (1) Take a test light; attach the alligator clip to the output side of the coil; and ground the "IcePick"end. (2)Then turn the motor by hand until the little notch on the crank pulley is just to the left of (passenger side) of the timing mark. (3)Turn the key on; and turn the motor by hand clock wise; when the test light lights up; that is where it is timed! The only time you really need a timing light; is to check the timing advance when you rev the motor.I set many cars timing back in the day using this method; before I could afford a timing light! Hope that helps you; Steve Lee This message was edited by sarahcecelia on 10-22-23 @ 1:53 PM
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| sarahcecelia | -- 10-22-2023 @ 1:50 PM |
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You do know the those 2 mixture screws are only for idle mixtures,right? Regards, Steve Lee
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| JayChicago | -- 10-23-2023 @ 7:03 AM |
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"I turned the left side needle to close and backed it out, did the same to the right side needle, I turned both sides 1 1/2 turns but the engine didn't change at all" That seems to me to be pointing to a problem with the carburetor mixture. I would not mess with the timing yet.
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| 51woodie | -- 10-23-2023 @ 7:13 AM |
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Istrum; If you have any question about your carb, send it to Charlie Schwendler in New York. I had problems with the carb on my '46 being over rich, even though I had confirmed the float setting was correct, and the "power valve" was correct and properly seated. I could not figure out what the problem was, so I sent it and my fuel pump to Charlie. He worked on both, tested them on his shop engine and I had them back in a very short time. He found that someone in the past had oversized the main jets, so he replace them with the correct size. The engine now runs clean, with nice light brown spark plugs. cas5845@yahoo.com 716-662-9159 I don't have any "timing marks" on the stock 59AB engine in my "46 Coupe, and unless you have a non stock engine, it is not likely your engine will have any either.
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| 37RAGTOPMAN | -- 10-23-2023 @ 7:26 AM |
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HI BACKFIRE with the air cleaner removed , and engine running,use a mirror and a light, see if there is dripping of fuel going down the carb, if it is it could be a needle and seat or a float problem, regulating the fuel also check the pressure from the fuel pump , it could be too much, I think 3 pounds is where it should be, might be a time to get a vacuum gauge and fuel pump tester , if you do not have one, test before replace, hope this helps, 37 RAGTOPMAN, Maine This message was edited by 37RAGTOPMAN on 10-23-23 @ 3:01 PM
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| istrum | -- 10-23-2023 @ 5:22 PM |
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Hello 51woody, Thanks for your input and you are right, I can not find a mark on my crank pulley.. I think I will contact CAS5845 thx again, Mike Jackson Thanks, Mike Jackson
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| JayChicago | -- 10-24-2023 @ 5:47 PM |
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Mike I think you are taking the right path. Charlie Schwendler is renown for doing excellent rebuilds.
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