Hey guys, I have a 77 2F, my dizzy literally just blew up with a bang and pieces all over the engine bay. Backstory, I only drive in the summer, and have only had it out a few times this year. I drove about a half hour away, pulling a trailer, to get new wheels and tires (and the trailer to lug the old ones home). New wheels and tires got installed, and some new kicks on my trailer, and right when I was backing out of the garage bay, my clutch slave cylinder bit the dust. No leaking, no warning. I managed to start up in gear and limp home, leaving the trailer behind. I just installed the new slave cylinder, started it up and BANG!. I do have updated ignition from a 78, getting rid of the points. Cap was damaged enough to just turn it over and the rotor is also destroyed. What would cause this?
Distributor cap blew up
- Thread starter Dianna
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Living in the Past
SILVER Star
I would check your oil dip stick for a smell of gasoline. An electric arch is not going to expose like that. Probably twenty years ago I used an old school self contained jumper start. It has an off on switch to isolate the jumpers battery. Are starting when I switch it off the the unit blew up. Only thing I could figure the vehicle was running at high idle and jump starter battery was leaking with the high charge from the vehicle's alternator. Battery in the jumper was sealed and believe it had a leak the the gases were contained inside the plastic housing..
The only time I saw a distributor cap blow up was when a coworker sprayed something in it to dry it out after washing the engine off. I don't remember what it was he sprayed as it was back in the 80's. Obviously he used something flammable.
I had one break apart after putting on cheap crap and rotor from the parts store. The rotor was hitting inside the cap. Pieces weren't all over the place.
I had one break apart after putting on cheap crap and rotor from the parts store. The rotor was hitting inside the cap. Pieces weren't all over the place.
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- Thread starter
- #4
All OEM parts, no startling fluid, etc. It started and immediately... BAM. I am just grateful it didn't do this on my long drive home, as I had to let it stall at every light and then start it up again in first or second gear to get home.
Does the vacuum advance work? Maybe gas fumes leaked in from the manifold thru the diaphragm. The OVCV didn't start until 78 so if it was hot and you don't have the carb fan the fuel can boil in the float bowl and get into anything connected to the manifold.
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If it wasn't from an actual explosion from a flammable substance under the cap, all I can think of is contact of the rotor and cap. Does the shaft have enough movement to allow the rotor to contact the cap? Are the parts old enough to have just failed/cracked enough to come loose where they contacted each other? Weird one for sure. 
Ozone? is that the stuff that builds up inside the cap? that's why there are those vent tubes on the cap that, in a 60, go to an inlet filter and a vacuumish source.
look in the 60s tech for more explosion stories
look in the 60s tech for more explosion stories
- Thread starter
- #8
This is going to be my issue. I retrofitted a line to my air cleaner, I drilled a hole to get vac advance, as someone here suggested. I had my hood open the whole time I was working on my clutch slave cylinder, and it’s hotter than the surface of the sun in Ohio here today. It was definitely an explosion, not just the rotor hitting the cap!
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So about 1976, in my wife’s VW Beetle, I was driving on the interstate and bang, car quit. When I lifted the hood (the one in the back of course), the distributer cap was in several pieces, hanging by the ignition wires. Lucky enough I had several of her hair bungies hanging on the shifter, so I bungied the cap back together, and made it home.
I had actually done this to myself, did a tune up that weekend, new cap, new plugs, points and rotor…..one of the clips that hold the cap wasn’t seated and the cap popped off, rotor hit it, and distributer cap carnage followed.
I ended up also replacing the distributer because the cap/rotor interference actually bent the rotor shaft…..for you, make sure the shaft did not get bent….have someone turn over the engine while you look at the shaft,,,,ensure NO shaft wobble observed.
Moral of the story….insure the rotor is fully seated on the shaft, make sure the cap is secured tightly, with the cap ‘key’ lined up with the notch in the distributer body.
I had actually done this to myself, did a tune up that weekend, new cap, new plugs, points and rotor…..one of the clips that hold the cap wasn’t seated and the cap popped off, rotor hit it, and distributer cap carnage followed.
I ended up also replacing the distributer because the cap/rotor interference actually bent the rotor shaft…..for you, make sure the shaft did not get bent….have someone turn over the engine while you look at the shaft,,,,ensure NO shaft wobble observed.
Moral of the story….insure the rotor is fully seated on the shaft, make sure the cap is secured tightly, with the cap ‘key’ lined up with the notch in the distributer body.
Living in the Past
SILVER Star
While it probably wasn't the cause I mentioned itgas on the dip stick is because if the diaphragm in the fuel pump is leaking you could wash out the bearings on the crankcase pretty quick. That's a bigger problem than a destroyed distributor cap. Doesn't take a minute to check and doesn't cost anything.
True, the ozone in there would be a strong oxidizer for anything flammable.
I don't know that I have seen one blow up, broken from bad bearing/bushing in the shaft allow the rotor to strike the contacts - yes. Wiggle the rotor toward and away from the engine and bumpers - it should have very little play.
Vac leak in the advance/retard mechanism could draw in vapors from the crankcase. Bad fuel pump, blow by from the rings, crack some where in the oil passage/gasket allowing combustion gasses in - 140 psi combustion pressure could leak into 50 psi oil.
Compression check dry and wet. +1 for oil sniff test or put in a diode electric fuel pump and bypass the mechanical for a while - makes a great spare, and you can transfer fuel easily.
Vac leak in the advance/retard mechanism could draw in vapors from the crankcase. Bad fuel pump, blow by from the rings, crack some where in the oil passage/gasket allowing combustion gasses in - 140 psi combustion pressure could leak into 50 psi oil.
Compression check dry and wet. +1 for oil sniff test or put in a diode electric fuel pump and bypass the mechanical for a while - makes a great spare, and you can transfer fuel easily.
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- #13
I should have mentioned, no gas smell on the dipstick. When you responded and didn’t know the answer, I knew I was screwed, lol.
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Big cap distributor venting?
Always something I’m not sure of! First picture is what was on her compliments of PO….. OEM air cleaner/carb has been on for quite a bit - Would the vent hoses off my distributor be routed correctly? So…. I can cross this off my not sure of list (search thus far hasn’t yielded a definite...
forum.ih8mud.com
- Thread starter
- #16
That is how I vented mine, drilled a hole to mount it in my air cleaner. Seems plausible to get fumes from there in intense heat that build up in the cap, right?This came up with the algorithm on the bottom of the page.
Big cap distributor venting?
Always something I’m not sure of! First picture is what was on her compliments of PO….. OEM air cleaner/carb has been on for quite a bit - Would the vent hoses off my distributor be routed correctly? So…. I can cross this off my not sure of list (search thus far hasn’t yielded a definite...
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- #17
I appreciate all of the responses, and saw how much editing I needed to do on my "voice to text" post from earlier, lol. I walked away from that mess after the cap blew up, left my tools and everything where they were because I tried to pick them up and they were like hot lava, lol. I went to a friend's house who has a pool for the rest of the day! I have a large cap dizzy I have been wanting to install, but still need to find a dented side cover. I guess I'll put that on the top of the "to do" list now. I hope it was just a fuel vapor issue, or maybe too much NOS. 
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- #18
I was disappointed to discover the cap is unobtanium 
Fortunately, I have a 78 parked in a field at my parents house and was able to battle the wasps under the hood (without getting stung) and pull the cap and rotor from that. Both of them appear to be new, I guess I am on the clock to find a dented side cover and get my 60 dizzy installed, or I should just bite the bullet before I get any older and weaker, lol, and stab the 60 series I bought from Gary a couple years ago. After I installed the cap and rotor, it fired right up and runs better than it did previously. The fuel vapors had to have traveled down the vac advance hose into the cap, but there is another vent on top of the cap that I would think would have exhausted the fumes enough not to combust. If my hood was as thin as modern day hoods, I have no doubt I would have a dent!
Thanks to all who chimed in
Fortunately, I have a 78 parked in a field at my parents house and was able to battle the wasps under the hood (without getting stung) and pull the cap and rotor from that. Both of them appear to be new, I guess I am on the clock to find a dented side cover and get my 60 dizzy installed, or I should just bite the bullet before I get any older and weaker, lol, and stab the 60 series I bought from Gary a couple years ago. After I installed the cap and rotor, it fired right up and runs better than it did previously. The fuel vapors had to have traveled down the vac advance hose into the cap, but there is another vent on top of the cap that I would think would have exhausted the fumes enough not to combust. If my hood was as thin as modern day hoods, I have no doubt I would have a dent! Thanks to all who chimed in
Well the chineesium Delco I bought off Amoron looks nice. I pulled the split ring spacer from my old real Delco, the cam gear and put it on the china unit. It fits and rotates but it not long enough to drive the oil pump - should have checked with the dial caliper instead of just using the eye crometer. Today I'll move the part back and re install the old delco. I guess I'll have make a new bushing for the top end, as the bottom seems free of play. The Delco was lock and I couldn't set the timing so at least that's fixed.
Update measured china with dial caliper seemed to be really close, removed their way to fat oring. Unit slipped in and with a little bumping of starter with the remote switch, it sat right down. Used key to whirl it over YEA OIL Pressure
Update measured china with dial caliper seemed to be really close, removed their way to fat oring. Unit slipped in and with a little bumping of starter with the remote switch, it sat right down. Used key to whirl it over YEA OIL Pressure
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