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Posted By Discussion Topic: 1937 starting backfire -- page: 1 2     mzahorik 08-27-2018 @ 2:40 PM reply profile send p.m. Member Posts: 209 Joined: Nov 2009 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 carcrazy 08-27-2018 @ 5:01 PM reply profile send p.m. Senior Posts: 1672 Joined: Oct 2009 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. mzahorik 08-28-2018 @ 7:02 AM reply profile send p.m. Member Posts: 209 Joined: Nov 2009 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 supereal 08-28-2018 @ 11:59 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 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 mzahorik 08-29-2018 @ 10:34 AM reply profile send p.m. Member Posts: 209 Joined: Nov 2009 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 mzahorik 08-30-2018 @ 4:35 PM reply profile send p.m. Member Posts: 209 Joined: Nov 2009 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 TonyM 08-30-2018 @ 6:51 PM reply profile send p.m. Member Posts: 459 Joined: Sep 2010 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 TomO 08-31-2018 @ 8:23 AM reply profile send p.m. Senior Posts: 7256 Joined: Oct 2009 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 mzahorik 09-01-2018 @ 7:24 AM reply profile send p.m. Member Posts: 209 Joined: Nov 2009 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 TomO 09-01-2018 @ 7:31 AM reply profile send p.m. Senior Posts: 7256 Joined: Oct 2009 Mike, I have seen new rotors that will move as much as 1/16". Tom

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