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EFV-8 Club Forum / General Ford Discussion / 1937 Backfire!

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Posted By Discussion Topic: 1937 Backfire!     mzahorik 06-27-2019 @ 12:15 PM reply profile send p.m. Member Posts: 209 Joined: Nov 2009 I've been working on eliminating the thru the carb backfire on hot starting of my 1937 Ford for a while. It is very annoying. The car starts fine cold, then for example drive to the car station for fuel, stop the engine for 5-10 minutes and restart. The engine would loudly bang through the carb and then refuse to start. You would have to wait 30-40 minutes to cool, before it would start again. This last week I have really dug into it and I think I have improved it some. First I found low vacuum. My windshield wiper motor was leaking, a lot! I plugged this off and the restart backfire was reduced significantly. BUT, now I had a after fire in the muffler, Just as load. So the first problem was a lean mixture, due to the vacuum leak. Now I think I have a rich mixture. And in fact I did. The float level was high. My fuel pump is fine 3# nearly on the head. The float needle seals great. But setting the Stromberg 97 float level is a bear. I tried to do it dry, but that didn't work. Doing it wet with the engine running is something I do not like to do, but that is how I found the float level to be high. After lowering the float level quite a bit, the car was a little hard to start, but no bangs! So I figured that maybe I lowered the float level too much. After raising it a little, maybe 1/16", it started better, but the back fire was back, only much smaller. My vacuum gauge reads about 17#, a little low. I figure that I either have another vacuum leak (the distributor valve is OK) or late ignition timing. My next step is to order an new intake manifold gasket. And check the timing. I wish there was a way to connect up my timing light. There has to be a way to mark TDC on the crank pulley and time this bugger. Mike ken ct. 06-27-2019 @ 1:32 PM reply profile send p.m. Senior Posts: 1513 Joined: Jan 2010 Float level MUST be set after your inlet seat fitting is tightend to the max. set at 1/4 " on the very end of float (flat section) opposite the hinge end. 3# is on the border line of too much. They run better at 1 1/2 to 2#. Idle mix screws out from stopped 7/8 to 1 1/4 turned out. I have been rebuilding strom's for 30 yrs. ken Isidor . 1-203-260-9780 MG 06-27-2019 @ 2:18 PM reply profile send p.m. Senior Posts: 1248 Joined: Nov 2009 Is the vacuum reading steady? Have you checked to see if the spark plug wires are plugged in correctly at the distributor - 1 to 1, 2 to 2 etc.? BUCKAWHO 06-27-2019 @ 2:34 PM reply profile send p.m. Member Posts: 96 Joined: Feb 2016 Hi....Timing.....you can use a twelve volt battery from another car to operate the light, then connect the light to spark plug wire as normal. BT mzahorik 06-27-2019 @ 3:06 PM reply profile send p.m. Member Posts: 209 Joined: Nov 2009 Ken, that is about where the float level is now. The needle fitting is in tight with a new gasket. Idel screws about 1 turn out, but they don't do much. Usually they will change the vacuum reading. So I think I hstill have a vacuum leak. MG, The vacuum reading is steady as a rock at 17" HG. I'm pretty confident that hte gauge is accurate. The spark plugs are wired correctly. Buck, I have thought of that, but what does one use for timing marks? Thanks Mike 40cpe 06-27-2019 @ 5:29 PM reply profile send p.m. Member Posts: 472 Joined: Jan 2010 Some have used fancy machined devices for a timing pointer, but most just use a stiff wire fastened under a bolt on the front cover and pointing to the front pulley. Use this pointer to make your reference marks by the dead stop method. If you aren't familiar with the dead stop method, we can fill in the blanks. TomO 06-28-2019 @ 8:22 AM reply profile send p.m. Senior Posts: 7243 Joined: Oct 2009 Have you checked the rotor for rotational play? Have you checked the inner caps for carbon tracking? Have you tried adjusting the vacuum brake with more tension? Have you checked the total dwell by connecting your dwell meter to the condenser tab on the distributor? If the car starts and runs fine , but just backfires when hot, I doubt if the initial timing is off by much, unless there is wear in the distributor. Each mark on the side is equal to 2 degrees, you can try retarding the spark by moving the slider. If this works, take the distributor off and send it out to have it repaired. You may still have a problem with the carburetor. Look down the throat when the engine is off and at running temperature. If you see fuel dribbling down the throat, have the carburetor rebuilt. Tom 37RAGTOPMAN 06-28-2019 @ 2:57 PM reply profile send p.m. Senior Posts: 1940 Joined: Oct 2009 hi I would start by taking a compression test and check the spark plug for being clean, if dirty could cause issues, check gap on the vacuum is the needle steady ? no flutter ? seems to me the engine is running to lean, maybe you have a clogged jet somewhere, how are the spray jets, are they pumping streams of fuel ? check with in engine NOT RUNNING, what is the compression in the motor ? all even,? maybe a sticking intake valve ? the motor run even, no misses,? When I went to school for auto mechanics, the instructor said the LAST thing you check is the carburetor, float levels do not change normally,. but floats go bad, I would start by removing one spark wire at a time, to see if it make any difference, while running, be careful use special insulated tool if one wire make a difference, this could be your problem, hope this helps, good luck my 2 censt 37 Ragtopman supereal 06-30-2019 @ 2:34 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Most backfires are due to a vacuum leak somewhere on or near the carb and intake manifold. A cracked hose to the windshield wipers is one common source. Another is a cracked fitting or line between the carb and the distributor, depending upon the year and type of he vehicle. Be sure the gasket between the intake manifold and the block is intact. Backfires through the carb usually ruin the power valve and let fuel seep into the intake, providing fuel for the backfire. To check, remove the carb. Be sure the bowl has fuel in it, and set it on a sheet of paper, If you find gas, you will know where the problem is.

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