Well, Here we go. Smack dab in the middle of the nicest summer we here in Buffalo NY have seen in my lifetime. I have had a intermittently poor running 1946 59ab Ford Flathead for 6 weeks now. Background: The car is 12 volts and other than being rich it has purred like a kitten for close to a year. Started easy. Idled very nice. Ran smooth. No issues. Then shortly after changing the fields in the generator from 6 volt to 12 volt, the car developed a stumble ( in the middle of a ride! ) under any load. Still it started easy and idled fine. I changed the plugs the other night with seemingly good results. Test ran the car and back to smooth running all around. I then ran it about 10 miles to an ice cream shop and my son even remarked " The car had never ran so smooth or sounded so good." Parked the car for about 40 min and when we left to go home the car ran horrible all the way home. Today I replaced the rotor first, no luck, then the condenser , still no luck. The stumble/ cough kinda clears up if I get on it hard. The battery, cap and wires are less than a year old ( maybe 500 miles ). The gas is good and flowing well. Stock mech pump with new diaphragm. Timing is like 17deg total with 18in of manifold vacuum. The stumble under load comes and goes suddenly. I'm stumped. Suggestions?
Sounds like a problem I had recently with a friends car I wasn't familiar with. I replaced many of the same things you did...plugs, points, condenser, etc. and sometimes the car ran great after making these changes and sometimes without warning or seemingly any reason, it would run like crap, if I could even start the car at all. Turns out there wasn't a ballast resistor in the electrical system. Could it be, now that your generator is putting out 12V, a resitor would bring the voltage down a bit where it should be? I found I was getting around 14V in the system, and basically cooking the coil, and causing it to run like yours is.
Yes a ballast resistor is in place. I have actually touched the coil after each outing thinking the same thing and it's only warm to the touch. I cleaned "filed" the points and no change either. The change from Champion plugs to Autolite 216s was a major improvement for two start ups only. And the voltage regulator looks fine ( clean as a whistle ) to me. Every bit of wiring in the car is new as of a year ago. and again it ran fine for close to a year.
Vacuum leaks can cause symptoms like this too. Runs great at idle, then when under load and vacuum drops, it stumbles and has no power. Had this problem too once, where a vacuum line was disconnected from one of those dual fuel/vacuum type pumps. The hose was actually sucking itself shut while at idle, and then when under load with less vacuum, it was opening up causing it to stumble or die. Check any potential vacuum sources for leaks?
Good eye! Someone was paying attention. It's a Hexagon intake. Road tested it yesterday after the rotor change and now not only does it stumble all the way home but it backfires too. NEW: I noticed the tachometer every once in a while, not read correct. Even drop to zero for a split second here and there. Could my tachometer be shorting out my ignition or could my tachometer be showing me my ignition/coil is skunked?
What type of distributor are you running? I'm leaning toward a short in your ignition not caused by the tach. Change those wires.
Just a curious question.....I noticed the fuel pump appears to run its output line (copper?) back into the firewall. Another copper line comes out of the same firewall opening and over to the carbs. Probably nothing to do with the current problems but I was wondering why the fuel system was plumbed that way.
Go back to basics, 3,things make a car go, fuel, air and spark. If spark good, and it should be after replacing most of the ignition system, i would look at carbs/fuel system, power valve, acc pump etc. look for dirt, blockages etc. I just put kits through my 97's, marked difference in drivability. Sent from my iPhone using The H.A.M.B. mobile app
Generator was polarized yes. But 97 I did have issues with the new generator making voltage. There may be something in what your getting at. The intermittent problems only started after the generator was changed. It's a stock crab cap dizzy. Mac VP the copper line appears to run into the fire wall but look close it just exits toward the rear and two 90 degree bends have the line coming right back to the carbs. Kind of an illusion. If the coil is going will a car idle well and clear up when ya romp on it?
Disconnect tach, as you can't yet tell whether that's showing an ignition problem or causing one. REMOVE THOSE LITTLE AIR CLEANERS AND GIVE CAR A SHORT RUN!!! Really! those things are often trouble, and this is a quick and easy test. Just two quick elimination tests before digging into ignition.
Definitely sounds like a primary ignition problem to me, too. I second Bruce's recommendation, disconnect that tach. (it is wired directly to the primary) Just have to remark on the clean layout and finish of everything underhood. Just gorgeous! My wife is anxious to build my '47 Merc flathead, this pic will light her fire for sure...
two questions... what is the disconnected hose laying on the intake... and are you missing an intake bolt?? sure looks like it edit, nevermind, just realized it's the alignment pin
That pic was taken at the time when I was wiring the car, and that hose is just a length of canvas sleeve to ultimately cover the few wires. Gonna pull the tach wire tonight when I get home from work.
OK When you changed the fields to 12 volt did you change polarity? ... if you are now negative earth the instructions for polarizing need to change too, the method also depends on how the new fields are earthed too. Did you use a new 12v regulator? If you changed polarity did you remember to change the coil primary wires ..i.e positive to power, negative to distributor/points. I ask this because you said the miss went away and then came back when you changed spark plugs. Saying that you also say it runs rich...depending on the fuel you use the plugs may well be incurably fouled... which will be exacerbated if the coil polarity is backwards.
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