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| | | | Joined: Jun 2023 Posts: 102 'Bolter | | 'Bolter Joined: Jun 2023 Posts: 102 | I’m running a reproduction carburetor and it has been running fine but it started backfiring in the carb last time I drove it. Any ideas what is going on. It is driveable like it is but I can even hear it slightly while I’m driving it. I’m wondering if the fuel mixture needs to be made more rich.
52 Chevy 3100
Jesus said to him, "I am the way, the truth, and the life. No one comes to the Father except through Me." -John 14:6
| | | | | Joined: Oct 2021 Posts: 6,761 'Bolter | | 'Bolter Joined: Oct 2021 Posts: 6,761 | Check all of your ignition components, first, including timing. Make sure your vacuum advance is working.
That said, the last time this happened to me, it turned out that the carburetor needed to be rebuilt. Since it was a FrankenCarter carb, I purchased a real rebuildable YF core and rebuilt it.
I believe the problem was the accelerator pump leaking or not working at all - I forget.
My experience with knockoff carbs is not good. Fake Autolite on '66 Mustang is horrible. I wish I had known how bad the modern knockoffs were before buying it.
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
| | | | | Joined: May 2015 Posts: 11,039 Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums | | Housekeeping (Moderator) Making a Stovebolt Bed & Paint and Body Shop Forums Joined: May 2015 Posts: 11,039 | An intermittent connection in the ignition wiring could also cause what you're experiencing. It would be like the points opening prematurely and firing a spark plug too early. Worth checking as well as the carburetor. I had a truck at one time that would backfire and die. I replaced the resistance wire from the ignition switch to the coil before determining that the coil connection (slip-on type) was loose. A quick squeeze with pliers fixed it.
Kevin 1951 Chevy 3100 work truckFollow this saga in Project JournalPhotos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together. | | | | | Joined: Mar 2010 Posts: 10,273 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,273 | The wire between the coil and the distributor goes through a lot of flexing every time the vacuum advance rotates the distributor. It requires a durable type of wire to withstand that for a long time.
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: Feb 2016 Posts: 1,985 'Bolter | | 'Bolter Joined: Feb 2016 Posts: 1,985 | If the ignition checks out ok, I would suspect a sticky/burned valve or an exhaust valve that is not opening.
1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy
| | | | | Joined: Feb 2004 Posts: 29,772 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,772 | I use high flex wire for multimeter test leads from the coil to the distributor. It has dozens of strands of very fine wire, and doesn't break at the terminal ends like normal primary wire. That wire is available on Ebay in a couple of insulation colors, usually red and black.
Jerry
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| | | | | Joined: Jan 2014 Posts: 3,681 'Bolter | | 'Bolter Joined: Jan 2014 Posts: 3,681 | Lots of good ideas, here. I’d favor the ignition theories mentioned above.
However, if you have a LEAN backfire that could do some ugly things in fairly short order. Might be worth at least checking the plugs to see if any are unusually light colored.
If so, lose the repop carb. Do that anyway, but do it faster if you see evidence of super lean running.
1951 3100
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