why did this happen????
 

soooo....my pickup has been running great. finally got the stop lights and signals working. i've been taking it out up and down my street to see how it's running. everything seems good. i backed it out today to do some body stuff. i was finished for the day and turned the key to put it back in the garage and BOOOOOMMMMM!!!! I'm real surprised somebody didn't call the cops. my ears still have some ringing in them

why in the world did this happen??????
'67 SWB 250ci

Re: why did this happen????
 

You may be running really rich and pumped a bunch of raw fuel through into the exhaust that ignited when you fired it back up.

Re: why did this happen????
 

ok, i am 2 turns out on the air/fuel screw. it had some minor sneezing through the carb and i had read i should open it up a little (air/fuel mix). I'm pretty sure i should start over with the tuning process. it was at 10*

Re: why did this happen????
 

When that happened to me it was from a broken timing change. One muffler looked like yours and the other one was like a pumpkin. But looking at all the soot inside of the case it is definitely running rich.

Re: why did this happen????
 

HAHAHAAAA!!! The same thing happened to me a long time ago! I thought someone took a shot either at me or near me... I jumped and sharted all at the same time...:exit: ohhh man I would have loved to have been a fly on the wall when it happened to me. Americas funniest material. My carb was very rich at the time too.

Re: why did this happen????
 

bet your timming chain is worn out

Re: why did this happen????
 

Whatever caused it had to do with unfired fuel then firing. So could be timing chain throwing strokes off. Same thing will happen when going down the road, shut engine down while in gear, and turning key back on. Raw fuel is pumped by wheels turning engine operating fuel pump with no spark, then spark, and KABOOM!! Could be just too much raw fuel, but probably combined with a timing issue

Re: why did this happen????
 

This exact same thing happened to me when I was 19, I had a 67 panel and the boys and I were ending our night with some grub. When we finished and went back to the truck, guys in back,(no seats) I started to crank it and BaBoooomm!!! One guy hurt his knee from banging it on the wood floor. I still laugh when I think of it.
Turned out to be nothing but a loose distributor. Had mufflers replaced the next day.

Re: why did this happen????
 

I thought the 250ci didn’t have a timing chain

Re: why did this happen????
 

When I was an idiot kid I used to do this intentionally. I once did it to a guy on a bicycle under an underpass... and you now know roughly how loud that must have been! You turn the ignition off, coast the engine, let it pump the exhaust full of fuel-air mixture, turn the key back on... BOOM. Though I somehow managed to never blow up my exhaust.

Anyway, now that I'm older and wiser, I'll just reaffirm what others have said here: unburned gasoline in the exhaust ignited.

Generally, you need some kind of a timing glitch to fire it off in the exhaust though. So there might be two different (or related) problems contributing to this one.

Re: why did this happen????
 

My math teacher in high school used to tell a story about his brother and their dads cadillac and that eventually they grenaded the muffler.

Re: why did this happen????
 

This is correct. The 250 has gears and I don't think they can wear out enough to cause this.

Re: why did this happen????
 

As a teenager, I had a 73' F100 that could easily do the same thing. Pass someone walking along the road, kill the ignition for a second or two, and watch them in the rear-view mirror, as they wonder what happened. And here I thought I was the only one.

The truck's still around, but parked in the blackberry brambles at the moment. It was my great-grandfather's last "go-to-town" vehicle. It needs a bit of work, but it's not leaving.

Re: why did this happen????
 

That's funny! When I was a kid! Imagine what I can figure out!!!!

Re: why did this happen????
 

This thread is the funniest thing I’ve seen all day! I know, I’m 30 but have the maturity of a 16 year old still. Thanks for the laugh Dave!

Re: why did this happen????
 

When I first looked at this, it appeared that there was hole in the bed. I was thinking about how loud that would have to be.

Re: why did this happen????
 

Had this happen on my 71 c10 250 6cyl. Was adjusting the points with a feeler gauge and hopped in the truck and the truck would not start. In my rush to admire my accomplishment i failed to re install the rotor. Then I goofed again and failed to put rotor in correctly. Tried starting truck crank crank and then the rotor must have been close enough to get a terminal and Boom, Blew the muffler wide open. . Wife and kids came running, ears rang for 2 days. On a positive note every piece of dirt and rust scale under the truck was blown OFF.

Re: why did this happen????
 

10 gauge or better by the looks of it! I am still chuckling...

Re: why did this happen????
 

I used to do that intentionally when I was 16 with my 65 c10 with a 283 manual choke and manual transmission with the same results. In this case it is probably due to a rich mixture and late timing.

Re: why did this happen????
 

I was out on New Years Eve on A1A in Florida doing this passing friends when one muffler blew out. True genius behavior considering the plan was to drive back to MD the next day. Such a nice ride listening to lop-sided exhaust up I-95 with a worn out steering box that made it like driving a tug boat. Real fun with out of state plates when a State Trooper would get behind me and I had to keep it moving steady w/o making a lot of noise and keeping my hands at the bottom of the wheel so he couldn't notice the excessive (1/3 turn) play. It was serious shuffle the wheel time sweatin' bullets keeping the blatter blap to a minimum. Never got pulled over, though

Re: why did this happen????
 

thank you guys for the replies!! i just got home and I'm fixing to go "re-do" the mixer and timing.

yes, y'all are correct about the gears.....no chain

thank you all again......I SAID THANK YOU AGAIN!!!!.........sorry, i couldn't hear myself saying it.....im still deaf:lol::lol: