Expect the unexpected...

[mk]

Wasn't sure where to post this, but I guess it falls under the category of always thnking about what you're doing and taking precautions.
Still, there's some things you just can't forecast...
A friend's got a '79 Dodge with a slant six that we suspect has a bad piston. I looked at it a couple of weeks ago, pulling plugs and valve cover to check it out and reassembling after I was done. Friend went out the other day to move it but couldn't get it started so I went over on wed nite to see why. Discovered the coil wire wasn't put back, so i did that and turned the key. Well, as it started there was a combination of a bang and whoomp and nice cloud of smoke that dissipated fairly quickly. Found myself looking at the valve cover sitting upside down on top of the engine, which was still running
Just before the valve cover lifted, the breather cap was launched straight up into the bottom of the hood and ricoched into the back of another truck parked about ten feet in front of the ol' Dodge. Sure blessed no one was standing there because they would have got a mouth full in addition to fried eyebrows...



mike

[robroy]

Good day Mike!

Found myself looking at the valve cover sitting upside down on top of the engine, which was still running

That's quite an event! The first time I read this, I misinterpreted it and thought that you found yourself sitting upside down on top of the running engine! I thought, WOW, that is quite strange, and must have been very uncomfortable, since sitting upside down even on some soft grass or a gymnastics mat isn't comfortable for many of us!

Robroy

[mk]

I'm guessing I'm going to find a holed piston when I pull that head this week as that's the only thing I can think of that would allow the spark plug to ignite the gas vapor built up in the crankcase. That little blast ripped off the bolted down valve cover and even pushed the dipstick out three inches.

mike

[Ranchero50]

Well, it is a Dodge...

Those slant 6's are supposed to be indestructible too...

[AlleyCat]

In his efforts to start it did your friend perhaps use ether ( starting fluid ) ?

[ford4x4fun]

[mk]

He's one of the best carpenter/builders around but not so much mechanically inclined. He said he just did lots of cranking and pumping the gas.

mike

[cdeal28078]

Was helping a friend on a 70ish Cuda with a built 383 try to get his started after some work. He cranked on it off and on for a while until I found the coil wire was pushed on but not enough. He cranked it again and all the gas in the exhaust ignited and ripped open 2 brand new Flow master 40 welded mufflers.
You think that is what happened here but maybe a couple exhaust valves were open enough at the same time that all of the blast went that way instead of the probably small, restrictive exhaust system?
clint

[mk]

This engine's had a dead cylinder for some time and a lot of oil is ending up in the air cleaner. I'm figuring an awful lot of gas must have been sitting in the cylinders from the attempts to start it and some found it's way into the crankcase probably via the bad cylinder. I'm looking forward to getting that head off so i can see if there is a hole in the piston as that's the only way I can imagine the crankcase fumes ignited. Got fresh batteries for the camera now so i can get a pic of the carnage on that valve cover.
I know guys that have had that 'expanded muffler' situation happen, usually after they've shut the ignition off at the top of a hill and then turn it on near the bottom. Makes a heck of a racket



mike

[DGrant09]

Glad to hear you two are ok Mike!!

These unexpected events are the pits.. I had a float stuck and filled the crankcase with gas.. Fortunately we did not try to start it before I checked the oil, which I do not always do.. I imagine we would have had quite the show if we had..

[mk]

Not necessarily... in a healthy engine, the spark is isolated from the crankcase by the piston/rings. This requirement is also the reason the pcv is a one-way valve, to keep a backfire through the carb from reaching the crankcase vapors.


mike

[DGrant09]

Thanks

[mk]

Finally got a pic...



Bad as it looks, it could have been worse. Note the hard fuel line over the head. The cover ended up flipped over under it; the force of the cover lifting pulled the fuel line out of the short rubber line from the fuel filter. As I was sitting on the edge of the seat looking through the gap between hood and cowl trying to process what just happened, I caught the sight of fuel spurting upwards from the fuel pump and it finally clicked that maybe it would be a good idea to shut it off



mike
( a thousand posts! )

[FreakysFords]

PURDY!!!! that valve cover's one for the shop wall.

Frank