Loud pop (backfire)....then died. Looking for confirmation on the problem. (1 Viewer)

[Major Nelson]

So I took my 77 out for a short drive yesterday. Everything seemed perfect -temp, oil pressure, volts.....about a mile from my house had a really loud backfire (literally sounded like a gun). Then the engine died. It wouldn't restart with the key, but I was on a slight downhill and just popped the clutch and it fired back up and was operating fine. When I went to slow down for the final turn it stalled again (200 yards from home). Towed it to my house and pushed it into its garage spot.

My first guess was it was going to be something to do with the carb....when i opened the hood I noticed the ventilation had popped off the PCV valve. After some more research I'm also thinking I need to pull the distributor to check the housing sub assembly and spiral gear.

Was hoping i'm on the right track in diagnosing the problem.

 

[micruz60]

Might have been built-up gases in the distributor?
That would be my first investigation, to make sure it was not grenaded internally.

 

[Pighead]

A backfire could blow the hose off the PCV, and introduce a large vacuum leak. Maybe why it didn't want to start. But why the back fire?
Naturally check your valve clearances, and your timing. And make sure every plug is sparking.
Probably not an exploding dizzy gasses thing, they usually blow the cap apart and it will not run even with bump starting

 

[Malleus]

I had that happen to me, when my smog pump exploded. Sent shrapnel into the engine. Bad day all around.

 

[1969FJ]

That happened to me and the issue was the distributor. The bearing on the shaft was worn and my timing was off also. I put a new distributor in, added pertronix, and timed according to vacuum and never happened again.

 

[tornadoalleycruiser]

HEI distributor? Or stock? Hei's can pull the shaft down and eat the magnetic pickup causing this issue

 

[Major Nelson]

HEI distributor? Or stock? Hei's can pull the shaft down and eat the magnetic pickup causing this issue

stock

 

[igotta40]

When mine did that it was just the ignition point gap, and the points contacts were pretty worn & burnt. It sounded just like a high powered rifle shot.

 

[Rookie Wrench]

I had the same, don’t remember who said it but the rule of “90% of carburetor problems are ignition” proved correct as usual

You are on the right track with the dizzy, check points and timing!