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EFV-8 Club Forum / General Ford Discussion / Rough idle and back fires out of exhaust.

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Posted By Discussion Topic: Rough idle and back fires out of exhaust. -- page: 1 2     Maine 10-20-2019 @ 11:31 AM reply profile send p.m. Member Posts: 8 Joined: Aug 2018 33/34 Ford Engine ran fine after recent machine shop complete rebuild. Trial runs totaled 20 mile showed high water temperature and so, the radiator was sent out for cleaning and review. The trials continued for around 30 miles with success with the temp around 150 degrees. After sitting for about a month I started the engine and it seemed to run rough and lacked power and backfired out the exhaust on deceleration . During the rebuild, I replaced the rotor, inner& outer caps plus the wires and one dist. bushing which had some play, reviewed the coil contact points and setting and lubed all that is asked for. The spark plugs were manually cleaned and reset as they appeared relatively new. I bought the car summer of 2018 it seemed to run fine but found compression low in one cylinder so the engine was removed to rebuild. In regard to the fuel system, The tank was new, but I replaced the fuel line, installed an inline electric pump, new diaphragm in the mechanical pump and checked the float level. My last activity to fix the rough running and backfiring exhaust was to clean the spark plugs 7 out of the 8 were very black and replace the condenser with no luck to fixing the problem. With the engine running, removing the secondary wire at each plug, the spark will jump a quarter of an inch on each plug white/blue spark. Any suggestions: supereal 10-20-2019 @ 11:50 AM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 Looks like an out-of-time problem. Best guess is that the timing gear has jumped a tooth or two. The fiber cam gears tend to get fragile from years of service, and tooth failure isn't rare. Check with the shop that did the rebuild to see if the timing gear was replaced. It is also possible that the crankshaft gear has sheared it's key. 40 Coupe 10-21-2019 @ 3:45 AM reply profile send p.m. Senior Posts: 1646 Joined: Oct 2009 So it ran OK and then it sat for a while, after sitting it then ran poor. It is very possible you have a valve sticking . You may want to try MMO to free the valve. It appears the Carb. is running rich, what Carb. do you have and was it rebuilt? Try a compression test it may tell you what cylinders have the sticking valves. You might consider thermostats to get running engine temperature up since 150 is low. Did you retorque the heads, at least once, after your trial runs? Check the fuel pressure at the Carb. If you have a Stromberg Model 40 make sure not to exceed 2 1/2# Maine 10-21-2019 @ 6:46 AM reply profile send p.m. Member Posts: 8 Joined: Aug 2018 The timing gear was replaced during the rebuild. Although I didn't do a compress test when I first installed the engine I did one during my diagnostic tests and they all registered between 70-75# which I thought was low even on a somewhat cold engine. The carb is a Stromberg don't know the model but do think it is and was running rich even before the problem. The float was checked and is at 3/16". Pictures in parts catalog looks like it is a model 48. Don't know the fuel pressure at this time and if it is high how do I tame it? the electric pump is the carter brand 2-4# pressure. Maine 10-21-2019 @ 6:52 AM reply profile send p.m. Member Posts: 8 Joined: Aug 2018 The heads were retorqued after the first running of the engine. 40cpe 10-21-2019 @ 8:34 AM reply profile send p.m. Member Posts: 472 Joined: Jan 2010 Maybe stuck valve/valves after being not used for a while? Run Sea Foam or Marvel Mystery Oil through the carburetor as per directions. rustedorrotting 10-21-2019 @ 8:37 AM reply profile send p.m. New Member Posts: 124 Joined: Mar 2010 just ran into similar problems on my 41. the power valve was leaking and filling my crank case with gasoline which resulted in a rod knock. check your oil level. there is a place called Charlies speed shop in Florida that sells an inline pressure gauge and pressure regulator. Some folks here don't care for him, but he has been very helpful to me. Maine 10-21-2019 @ 11:57 AM reply profile send p.m. Member Posts: 8 Joined: Aug 2018 Talked with Jeff at the shop that rebuilt the engine. He can't come up with why the timing gears would fail so early, fiber gear is new and all press fitted tight. after further discussion on my activity he determined I should address the rich fuel problem. This was based on my the running of the engine right after recleaning the spark plugs. The engine ran fine for about 15 minutes smooth and the turned rough again and started to backfire at the exhaust when dropping back to an idle. I can't smell gas in the oil but it does blow black smoke when it runs rough. The carb is a Stromberg 97, and at this time, I don't know the jet size nor do I really know the vintage of the engine. the heads are 19 bolt cast iron. i MG 10-21-2019 @ 12:28 PM reply profile send p.m. Senior Posts: 1248 Joined: Nov 2009 Is the mechanical fuel pump new? Some of the new fuel pumps (off shore) out there have excessive pressure. There's been a rash of reports of the symptoms you are experiencing caused by excessive fuel pump pressure. Ideally you want 2-1/2 lbs. pressure - no more.... 37RAGTOPMAN 10-21-2019 @ 3:09 PM reply profile send p.m. Senior Posts: 1940 Joined: Oct 2009 HI Maine did you try using MARVEL MYSTERY oil in the fuel, I think you have sticking valves, especially the exhaust valves this happens when the engine is not broken in and sits idle for a period of time, worth a try ,,,,, also with the engine running, use a light and a mirror and look down the carburetor and check to see what is happening, is gas flowing over ?maybe a bad float or needle valve, causing overflow down the throat of the carb ? causing running rich hope this helps 37RAGTOPMAN MAINE This message was edited by 37RAGTOPMAN on 10-22-19 @ 10:23 AM

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