KABOOM! when hitting headlights.....

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clementine

Flight risk
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Took out duster this morning to go to remodel job I have been chipping away at. 12 miles one way. 72 /6 duster...stock... Dude was sleeping so I spared him the noise and chalked it up to having a cruise with little traffic. Back in car about 5 miles into trip home and under light load up an on ramp and I hit the headlights on.....sounded like a gunshot, very crisp. Lost power for a split second, hand was still on headlight switch so power off on switch, car regains power and Im off on highway and ran fine all the way home. left running in drive for visual inspection, nothing jumped out at me. turned on/off/on/off headlights with no symptoms.

1. There was a harder than normal start this morning, ususally a two pump and touch the ignition to start and goes right to high idle.

2. I have a small exhaust leak at manifold but only something heard under power...very small.

3. A year ago I drove it 40 miles to adjacent town and had the carb (1bbl) loosen up on me and got her tightened and then no prob.

4. It needs some adjustment as in drive idling it will have a slight miss or something every 3 sec or so. Seems timing related.

5. I have a lockout something or other disc with little square holes in it that I havent put in....just been driving it.

Where did the shot come from? I would assume through the exhaust but I have not heard any more of an exhaust leak, no hole in muffler.

Need to check plugs......but I thought Id be lazy and just ask you:rolleyes:
 
Check your ignition wiring. Both times I had this happen (more than 30 years between incidents) was due to interruption in ignition. The first time was a loose coil wire. The second was a broken distributor lead. Unburned fuel momentarily accumulated in the exhaust. When ignition was restored, it lit off the fuel with a boom.
I have no idea how your headlight switch could be part of the equation.
 
Check your ignition wiring. Both times I had this happen (more than 30 years between incidents) was due to interruption in ignition. The first time was a loose coil wire. The second was a broken distributor lead. Unburned fuel momentarily accumulated in the exhaust. When ignition was restored, it lit off the fuel with a boom.
I have no idea how your headlight switch could be part of the equation.

You spelled out most of what likely happened but missed the bigger picture... The headlights drew enough power to cause the point of high resistance (probably the bulkhead connector) to momentarily go open.. Thats what cut the ignition but the engine was still turning so air was still passing through the carb which caused the exhaust to get loaded with fuel, when the circuit closed & the engine fired again it lit the fuel in the exhaust...
 
You spelled out most of what likely happened but missed the bigger picture... The headlights drew enough power to cause the point of high resistance (probably the bulkhead connector) to momentarily go open.. Thats what cut the ignition but the engine was still turning so air was still passing through the carb which caused the exhaust to get loaded with fuel, when the circuit closed & the engine fired again it lit the fuel in the exhaust...
Well, if that's not reason enough to put headlights on a relay, I don't know what is.
Both times it happened to me, it was a much more obvious cause and effect.

See the broken lead?
100_0809.JPG


The result:
0503131058-00.jpg
 
Well, if that's not reason enough to put headlights on a relay, I don't know what is.
Both times it happened to me, it was a much more obvious cause and effect.

See the broken lead?
View attachment 1715959850

The result:
View attachment 1715959857

Nice!!! :lol: I did that once... It wasn't quite like yours, I shut the ignition off intentionally attempting to create a backfire... But left the ignition off just a little to long... :rofl:
 
It was a blessing in disguise. Those were Hooker High-Drones that literally sucked out loud.

My brother showed me ignition switch backfire trick on our old F-100. The muffler on that was probably for a semi. It was four feet long and at least eight inches in diameter. He didn't blow it apart, but it wasn't for lack of trying!
 
Ill check the ignition wiring. I blew up a muffler after forgetting the coil wire during a start after swap.

But heres the thing. When I pulled the headlight switch, It first 'boomed' then died for a spit second. I dont remember it having any time to load the cylinder.

Ill check ignition.
 
Clean your bulk head connection. The load of the lights cut the main power to the ignition switch for a split second. . It will be the fusible link wire at the bulk head. They always get corroded due to the material they are made of.
 
Clean your bulk head connection. The load of the lights cut the main power to the ignition switch for a split second. . It will be the fusible link wire at the bulk head. They always get corroded due to the material they are made of.
When I take that puppy apart to inspect/clean....am I supposed to use diaelectric grease in there? I still dont understand that stuff. Is it for grounds only?
 
The ends come out of the bulk head, Clean them and then use dielectric grease. I remove harnesses glass bead the whole bulk head and all the ends on all used harnesses if corroded while together in a cabinet. I only use clean fresh glass beads that have not been used for cleaning parts. It actually cleans without dulling parts, Plastic and metal.
 
Sorry Dave I've no idea. Hope you guys had a good trip out east and back
 
Well Ill try to update this thread when/if I figure it out.
I almost sounds like the lamps have a short somewhere, or the voltage dropped low when they were activated, the coil could have simply discharged a spark at the wrong moment when that occured, causing the bang. Were You talking an FBO plate to limit the mechanical advance?
 
Yes. I havent put that in yet......you running one?
No, but I may on My SB project, I checked them out a while ago. Have to see what advance slots I have in the "collection" here first, may not be needed.
 
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