Missing 40 flathead

68HILLBILLY

68HILLBILLY

Senior Member
hi guys need some help from some experienced flatheads. my 40 sedan started missing bad all of a sudden yesterday. fuel pressure seems fine( fills a pop bottle quickly) not running rich , idles but not as smooth as before .checked voltage to coil it is about 6 full volts with engine off ig. swtch on (sounds like resistor is not working). has a good strong blue spark on drivers side cylinders weak (very weak on all 4 passenger side cyl.s. I believe it is a rotor or points issue on pass. side of dist. This is my first running and driving pre war v8 ford so I need a little help. does the dist. have to come out to service the points and rotor button? looks like it does. can dist only go back one way? have a 39-48 manual but it doesn't show this operation , shows mostly the newer crab cap dist. any advice or thoughts appreciated . is there a shop manual better for just the 40 model? by the way already replaced the condensor and car does have modern coil adapter kit. thanks
 
could be loose spark plug wires one the pass side inner cap. Points will not cause this, nor will a rotor button cause this. I have seen the plug wires pulled loose from the inner cap and still look ok on the outer cap.
 
If you have a modern coil on there you will need to know if it has an internal or external resistor. You might be running through two resistors.There are two sets of points but they work together to get a long dwell , one set is not designated to one side of the engine. If it were mine I would find a stock coil and have Skip in Fla. to rebuild it and make sure the resistor under the dash is good.
 
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>>>started missing bad all of a sudden >>>blue spark on drivers side cylinders very weak on all 4 passenger side >>>

Check inner caps both sides before digging any deeper.

Jack E/NJ
 
I'm going thru the same thing. Had Bubbas rebuilt the dizzy, replaced the coil. Now i'm going to check spark wires for grounding out or weak spark at the plugs. Ran good until i left the switch on still can't find the problem. These Flatheads...
 
Check the passenger side inner cap to make sure the wires are seated in the cap and that the cap is seated in the distributor. Make sure that the gasket is between the inner and outer caps and that the bail locks between the 2 bumps on the outer cap.
 
THANKS for all the info , we are having some nice weather right now and was hoping to drive it some more before winter. thanks
 
Ken Crans said:
I'm going thru the same thing. Had Bubbas rebuilt the dizzy, replaced the coil. Now i'm going to check spark wires for grounding out or weak spark at the plugs. Ran good until i left the switch on still can't find the problem. These Flatheads...
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Ken; You may have fryed :mad:( burnt ) the contacts in the ingition switch its self. and or the wire from the switch to the resister on the firewall. and the wire from the resister to the coil, you can "ANNEAL" a wire to the point it will show voltage at the other end, BUT not carry current (:confused: amps) to fire the coil....a quick check, run two parallel wires, both "sw.to resister"... and "resister to coil" try to run the engine, for ...is it fixed ??
Now to the ing sw. take the wires off and mark em.... the two screws that hold it on the column drop is the what holds it together, wrap some masking tape around the switch to hold it together, take the two screws out, and the sw. comes off and stays together, when you open it up, be somewhere you can keep everthing together, there are some small springs,and and a sliding contack , to clean and keep in place. sorry to be so longwinded, ..hope it helped ...or makes sence..... OLD....BILL :cool:
 
Dual points one set may have closed on you, my 36 runs rough when that happens. Check simple things first.
 
Thanks for all the info.. I will try the jumper wires. Hey Hillbilly, did you get yours fixed? i looked at the wires in the caps. Looks like they are loose. That's probably the problem. Just got back the dizzy from Bubba for the second time. i need to get it all back together to see what happens. thanks guys.. . Ken
 
TOOK the caps apart on dist. everything looked ok but was not able to work on it too long . still running rough. had to go to work (2nd shift). will dig a little deeper later this week. thanks again for all the info. and good luck with yours as well. when I get it fixed I will post the problem. believe it is something minor that just popped up this past weekend. had always run fine before.
 
same thing just happened on my 40. pull the dist. take off the coil. make a mental note of the timing mark and then remove the bolt. now remove the large nut only on the advance and it should keep its settings. slide the center section out of the back of the housing and then you can remove the rotor off the center shaft and have ample clearance for adjusting the points. mine seem to have worn where they ride on the octagon in the middle so i had to put a rat tail file in the adjusting hole of the bottom plate of the points and open it up a bit. to get my .013 gap. but it sounds much better now. im gonna switch to a crab with bubbas electronic conversion so i can avoid this happening again in the future. now reverse it and make sure when you put it back to pay attention to the offset of the tab on the back of the dizzy.
this is what i did if anyone has gripes with it i just dont know any better. feel free to tell me im wrong. but this seemed to help me. good luck
 
If you left the ignition switch on the insulation in the coil could be damaged. Get a stock coil rebuilt by Skip and end your coil problem for ever. Also I have seen several rotors that the phonolic material broke down internaly and the brass bus bars which carry the spark from the brass brush band to the ends of the rotor jump a spark to the shaft that the rotor is mounted to. When the phonolic is black that is carbon and acts like a resistor which carries the voltage to ground. This is a resistive short, not a dead short. G.M.
 
>>>blue spark on drivers side cylinders very weak on all 4 passenger side >>>

Since it seems to be a unilateral problem, check for crossfire or leaks in the spark plug wires if they're old. Are they bundled together in the old steel tubes? Related to what GM suggested, what kind of condition are the caps in? If a rotor was leaking to the shaft, it would likely affect both sides not just one side.

Jack E/NJ
 
wires are older and still in the metal tubes, I just don't want to start changing everything out. all these thoughts and ideas give me a lot of things to check , I just need to be patient and check one thing at a time so I don't have to back track or buy everything new. thanks again.
 
If its weak on one side it can only be cap .wires or plugs .Check again that its not weak on all .run a jumper wire direct to the coil .from the battery .run this for only a few Min if without the resistor
 
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Thanks for the input you guy's are offering. Got the truck running today. She flies now. I was the one who left the switch on, burned up the points. Had Bubba rebuild the dizzy and put it back in and didn't run right. Seems when i took the outer caps off the helmet one of the wires came loose. and the external coil wire was bad . Long story short, i got it back together and no miss! Thanks Friends Ken Crans
 

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