| mzahorik | -- 08-27-2018 @ 2:40 PM |
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I finally got my 37 ford to start and run good, but there is a (sometimes LOUD) backfire right at startup of the engine. There doesn't seem to be a backfire problem at other times. The car also seems to have an exhaust leak. I can not hear a loud exhaust note, but when driving with the windows open you can smell the exhaust. I'd like to correct this backfire, where should I start looking? Thanks Mike
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| carcrazy | -- 08-27-2018 @ 5:01 PM |
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Does it backfire through the carburetor or out of the exhaust? Intake backfires can be caused by too much spark advance or too lean a fuel mixture. If your car only backfires right after a cold start, I would suspect that it is too lean at that point. You can minimize this lean condition by using a little more choke until the engine warms up.
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| mzahorik | -- 08-28-2018 @ 7:02 AM |
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Thanks for the reply. Yes, it backfires thought the carb. Puzzling though, sometimes it sounds like a cannon and other times almost nothing. This kinda led me to believe that maybe there is a leaky valve? Anyway, It's been so warm these past few months that I have not used the choke at all. This morning, I drove the car to the gas station, which is less than a mile away. After that short drive and the car sitting for the time it took to fill and pay for the gas, the backfire sounded like a 105 going off. I'll try the choke, but I think there is more to this problem. Thanks again, Mike
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| supereal | -- 08-28-2018 @ 11:59 AM |
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Check both distributor caps for carbon paths. They are hard to see, but act as a short circuit. If you have original spark plug wire is the metal conduits, that can also cause crossfire that will cause backfire thru the carb that will eventually destroy it. This message was edited by supereal on 8-28-18 @ 11:59 AM
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| mzahorik | -- 08-29-2018 @ 10:34 AM |
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Well.... for the last couple of days, I've been starting the 37's engine in a different way, in an attempt to see if enriching the mixture would help. With the engine cold and the ignition switch off, I'd crank the engine for 1-2 seconds with the choke closed. after that, start the engine as normal. So far so good no backfires, but I have to watch for flooding it, which I did once. So I connected the vacuum gauge and I get a steady 19 inches. The needle is not perfectly steady, the needle will move about the thickness of the needle, but I think that is OK for the age of my motor. That makes me think that there is no vacuum leak or it is small. What else would cause a lean mixture? This motor has the metal conduit for the spark plug wires. Recently I redid the distributor and closely checked the caps etal. Looks OK. What would you suggest about the conduit? Temporary run separate wires to isolate crossfire? Mike
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| mzahorik | -- 08-30-2018 @ 4:35 PM |
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Well..... I have tried a half dozen cold starts with just using the choke being pulled out half way, again no backfires. My other cars do not require the use of the choke at all until the temperature drops to 45° 0r 50°. Not sure I know why, but I can not argue with success. I'll have to learn how to start this car exactly, when warm. Thanks for the help. Mike
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| TonyM | -- 08-30-2018 @ 6:51 PM |
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The 1937 Ford Owner's Manual states "Pull the choke button out" before starting the engine. After the start then push the choke button in to maintain smooth running as the engine warms up. When engine warms up, push choke button all the way in. I start my stock 1937 Ford in this manner with no problems. . . . 78-730B
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| TomO | -- 08-31-2018 @ 8:23 AM |
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Mike, Backfire through the carburetor can be a timing problem. Remove the distributor caps and try to move the rotor in the plane of rotation. If it moves, you will have to replace it. You should also check the timing of the driver's side set of points. If they open too soon (gap too wide) it will give you a more advanced timing. The timing check should be made on a distributor machine, by a competent operator. Also do the checks that Supereal suggested in his reply. I would be concerned with the exhaust leak. CO is odorless and could be filling you cabin without you knowing it. Use your hand to feel for exhaust along the manifolds and pipes, if you cannot hear the noise of the exhaust escaping. Tom This message was edited by TomO on 8-31-18 @ 8:24 AM
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| mzahorik | -- 09-01-2018 @ 7:24 AM |
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The ignition should be sound. I had the coil rebuilt, the points were set on a machine. The caps are new. Although I still have to something with the spark plug wires. The exhaust seems to be leaking at the junction between the cross over pipe and the exhaust pipe. There is a slot in the exhaust pipe that allows the pipes to easily go together, the end of the slot is open to the air, maybe 1/8". I can see a black soot trail there. Same thing at the back of the muffler and the tail pipe. Also a small leak on one of the muffler seams. I don't see anything at the exhaust manifolds to the block. I had them off a few years ago looking for the same thing. The pipes are rusty but seem solid and the muffler still has much of the galvanizing on it. Hate to spend money on something that still works. I'll try and seal it up prior to replacement. Thanks Mike
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| TomO | -- 09-01-2018 @ 7:31 AM |
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Mike, I have seen new rotors that will move as much as 1/16". Tom
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| mzahorik | -- 09-01-2018 @ 12:52 PM |
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OK, I recheck it. Could be when you are not looking for something you can miss it. The next item to change will the spark plug wires, to see if that changes anything. I have been trying to drive the car everyday. Today when I thought that the engine was warm and would not need the choke, I didn't use it and there was a mild backfire. Maybe it is more than just the choke. Mike
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| mzahorik | -- 09-01-2018 @ 1:08 PM |
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Started to look around for new spark plug wires. First my old ones are not original type. They are the more modern rubber insulation with a 90° rubber boot on the plug end. Looking at the vendors they have what looks like cloth covered wire with bare ends. I'm not looking for appearance, but want functionality. I'm thinking that the new more modern ignition wire would be better. Any opinions? Mike
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| carcrazy | -- 09-01-2018 @ 7:01 PM |
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Use the original type of spark plug wires which feature the solid metal core wires. These wires won't lose conductivity due to heat or age. They are readily available from MAC's and many other vendors at reasonable prices.
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| mzahorik | -- 09-03-2018 @ 8:41 AM |
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Today I started to look for the exhaust leak. But the big problem is that it's HOT! So, after the parts cooled off, I made an adapter that connected my air compressor to the tail pipe. I throttled down the pressure and turned it on. I was surprised that the exhaust manifolds and manifold to pipe seems to be fine. The big leak is at the back side of the muffler. I think I can get those parts apart in seal it up. Then I'll apply the compressed air again and re check the more down stream connections again. GEeezzzz, now it's raining again. Mike
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| mzahorik | -- 09-04-2018 @ 12:50 PM |
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Well..... it finally stopped raining and apparently we are not to get anymore for a couple days. I can't remember such a wet August/Sept in my 70 or so years. The compressed air found two significant exhaust leaks. I bought some Permatex exhaust sealer and pasted up the holes. Seems to work. It should hold until I can afford a new exhaust system. My old system seems to have been a cobbled system, but is still in good enough shape to last for a few years. I also checked the sloop in the rotor. There is some, but not 1/16", maybe 0.020" or so. Anyway it's too hot to do more today. Mike
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| mzahorik | -- 09-05-2018 @ 7:16 AM |
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Last night while driving the car, the fan belt was torn up. Today i have to find a replacement. Mike
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| TomO | -- 09-06-2018 @ 6:49 AM |
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Mike, any rotational movement in the rotor with the engine stopped, will affect engine timing. If you continue to have the backfire, have the distributor serviced by a competent shop. Tom
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| mzahorik | -- 09-06-2018 @ 7:44 AM |
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Tom ,there are three places that there can be some of this sloop. 1st between the rotor and the shaft, 2nd between the shaft and the cam adapter and then between the adapter and the cam. I have an older distributor on a newer engine. Somewhere along the line, the car got a short block, a 59A. The older attachments were retained. I don't think that I can remove the amount of sloop that exists here. If there is 0.030" sloop divided between these three spots. Next time I have the distributor out I'll check to see if I have a better shaft. Thanks for the help, I appreciate the insight. I found a belt at Tractor Supply and it was only $17. Mike
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| paulb@remax.net | -- 10-02-2018 @ 1:40 PM |
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Sorry for the ignorant question, but I thought pulling the choke out cut off the air supply thus making the gas mixture leaner or richer. Sounds like it works, but seems to be the opposite of what logic suggests.
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| mzahorik | -- 10-03-2018 @ 8:53 AM |
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If you don't ask questions, you will never know. When you pull the choke out the mixture will become richer. I think what is happening is with a lean mixture, the burn time is much shorter and the flame will burn while the intake is still open. With a richer mixture, the flame time is retarded and the intake valve has more time to close before the flame front reaches the intake valve area. This is my thoughts anyone else is welcome to chime in and correct me if needed. Thanks Mike
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