Topic: occasional miss


fenbach    -- 06-04-2014 @ 7:06 PM
  my '36 runs fine except for an occasional miss. no regular pattern to it, just a momentary hesitation now and then as if someone shut the engine off for a split second. it feels like one piston just doesn't fire now and then. of course, i can't tell if it's always the same cylinder. i have a skip haney coil and a recently rebuilt distributor. but can't remember if the miss coincides with the rebuild. advancing the timing a few degrees didn't make any difference. i haven't tried retarding the timing yet. any ideas??
thanks.


fla48    -- 06-04-2014 @ 7:44 PM
  Have you tried the resister on the coil, or inside the distributor for arching?


TomO    -- 06-05-2014 @ 7:33 AM
  Have you checked the ignition switch for worn contacts?

Tom


supereal    -- 06-05-2014 @ 7:42 AM
  I would expect an ignition problem, likely sparkplug or plug wires. If you have nonmetallic plug wires, or the regular type, one or more of the end terminals may not be making complete contact. With metal type wires, we solder the terminals a both ends. If your plug wires are older, there may be a "leak" inside the conduits from cracks in the insulation. Inspect each spark plug to see if it shows deposits. If black instead of tan, it is probably being fouled. A skip now and then, particularly when under load, such as a steep grade, isn't unusual. It is also possible that you have a sticky valve or a weak valve spring. A compression test will tell you if the valve train is involved. A bit of lube, such as Marvel oil in the gas, may help, but don't overdo it, or plug fouling is likely.

This message was edited by supereal on 6-5-14 @ 7:56 AM


fenbach    -- 08-09-2014 @ 7:38 PM
  i think maybe the rotor was shorting the spark to ground now and then because i see a small crack on the surface of the rotor starting at one of the 2 tips. that's my best guess, anyway, but i couldn't get it to short out on the bench. i had the distributor out twice, cleaned it and put in an NOS rotor, but i'm not 100% sure the rotor was bad because i was swapping parts and making adjustments all along. i also wiped some oil off one of the moving point arms. i'm not about to remove the distributor again any time soon to retry the old rotor! but i'll send it free to anyone who wants to experiment with it.
i didn't do a compression check, but did hook a vacuum guage to the intake manifold. the reading was absolutely steady. i also put in new plugs and new plug wires early on. they didn't make a noticeable difference. the old plug tips looked good. and the resistor was good.
the tips of the plug wires that i got from bob drake weren't soldered to the wires, by the way. which probably won't make a difference with such high voltage but still and all worth doing, and easy enough, i'd say.
thanks for all the suggestions. lastly,
using a couple cut off bolts to position the distributor on the engine is a tip well worth repeating i have to think.

This message was edited by fenbach on 8-9-14 @ 7:48 PM


supereal    -- 08-12-2014 @ 8:26 PM
  We always solder the terminals on both end of each plug wire, and the high voltage wire from the coil to the distributor on models where the coil is not distributor mounted. This requires metallic wires. The carbon filament cables are an invitation to problems, and should be avoided. Don't count on the voltage to both jump a gap and fire the plug.


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