| tubetype | -- 07-15-2015 @ 11:44 AM |
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51 ford-vic. with large 4 barrel carb. Engine missing at high RPM. Plugs and wires OK. Timing correct with vacuum from carb ok. Has electronic ingnit. Dist. cap looks OK. Can't tell if it ingn. or fuel starvation. Any thoughts. BUD
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| ken ct. | -- 07-15-2015 @ 6:22 PM |
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Are you running with original loadamatic dist,if so you could have a vacume issue.Orig. does not use normal vacume. OMO. ken ct.
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| TomO | -- 07-16-2015 @ 7:19 AM |
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You can check for fuel starvation by performing a fuel delivery test. To check fuel delivery, you need a graduated 16 ounce or larger container to determine the amount of fuel delivered in a measured time. Disconnect the fuel pump line from the carburetor and direct it into a graduated container. Crank the engine long enough to get 2 ounces of gas in the container and then continue cranking for 15 more strokes of the pump. The pump should have delivered 6 more ounces of gas. The electronic ignitions have been very troublesome on the old cars. Tom
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| tubetype | -- 07-16-2015 @ 2:40 PM |
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Dist. has vacuum advance. As back up I have electric pump.No difference in higher RPMs.. Holding at 60 MPH (when missing starts) I have tried pumping the accelerator and get no change. Could I have sigh speed jets clogged in the carb.. I ready to put in points and Cond. to replace electronic device.???? BUD
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| TomO | -- 07-17-2015 @ 6:51 AM |
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Bud, You could have a plugged fuel line and pumping the accelerator or using the electric fuel pump would not help the problem. Do the fuel delivery test and if the car passes that test, then look for ignition problems. The stock Ford distributor requires ported vacuum for the vacuum part of the advance. A change from the stock carburetor could affect the advance curve and drivability. I don't have any experience with electronic ignition on the flathead, so I cannot give you a good diagnostic approach other than going back to a point ignition and a stock carburetor. You may get a diagnostic approach at the HAMB. Don't just start replacing parts unit you go broke or fix it. Going back to stock would make it easier to give you a diagnostic procedure. Tom
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| tubetype | -- 07-20-2015 @ 8:32 AM |
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Thank you for your thoughtful replys. Fuel test and then if necessary place with points. BUD
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| carcrazy | -- 07-20-2015 @ 1:20 PM |
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An engine can miss at higher loads due to several different causes. Ignition which is adequate to fire the spark plugs at idle and low speed/load conditions may not be sufficient with the increased combustion pressures generated at higher speeds. Are you running solid metal core spark plug wires of low resistance with effective insulation. Are the spark plugs set at the proper gaps for the ignition system you are using. If the gap is too wide, the spark won't be able to jump it at high speeds. The secondary main metering system of your 4-barrel carburetor may be too lean to support combustion once you open up the secondary throttle plates. There could be blockages in either the air inlet tract leading to the carburetor or the exhaust system that are choking off airflow through the engine at high speeds.
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| DD931 | -- 07-23-2015 @ 3:24 PM |
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If the problem is worse when accelerating at high RPMs it's likely to be the plugs.
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