Some of you likely saw where we had some fun (that I instigated) after with Scott @ Harms blowing up a muffler on his test stand.
It was a tune-up issue on initial startup.

Well, Karma, I guess.

Yesterday I'm driving my K10, with the buddy I'd bought it from years ago, just cruising along about 30 MPH.
Truck's been running like a watch, not a hot rod by any means, just a nice restored truck I'd just driven about 35 miles, speeds 25-60.
Suddenly it starts popping loudly and intermittently out the tailpipes, kinda like shutting off, then clears up but it's a lot louder.
Drove it about 6 miles home where it ran perfectly, just...louder. (Obviously it had hatched at least 1 muffler.)
Exhaust is just basic 2.25", "Xcelerator" brand "turbo" mufflers, H-pipe, about a year old.
Blew right muffler apart, left is swollen up like a puffer fish.

I'm wondering what the heck caused that, when the thing's running fine. Even the tailpipes have that nice medium tan/grey color inside.

That same scenario is pretty much what happened to my. I had a plug wire pop off one plug and that was enough to do the deed.

I forget what exhaust I had on it at the time, whatever chain store system the PO put on it but it popped the muffler.

So I had a mom and pop shop put in a full exhaust with a crossover and dual flowmasters. That thing sounded good.

Yeah I get that, or if the tune was way off. I've owned the thing 10 years, never an issue like that.
It's not too rich, no misses or anomalies, cruising smoothly as could be under basically no load, then BANG.
Felt like it was running out of gas right when popping out the exhaust, resumed its normal smooth running after a minute or so of trying to blow the mufflers off.
Tried to induce it accel/decel at the time, and afterwards, neither had any effect that would indicate a problem.
I'm gonna poke around at wiring, plug wires, and the HEI and see what's up.

An ign component went out makeing a part time miss on some cyls, letting unburned fuel exit from those cyls & travel downstream & the muffler ignited it makeing it explode. The coil would be my guess

That sounds like it,something shut off the ignition or spark momentarily and boom! Could even be a worn ignition switch itself.
RT

I think I found the problem.
Gut instinct was to look at ignition.
So, got to looking at the HEI, pulled the coil & cap, and the center button was in a couple of chalky pieces.
You could see a trail of powder running in 2 opposing directions.
How that thing ran so well coming home is beyond me.
I'm guessing that the button broke, and as it disintegrated there was a bit of crossfiring that went through the exhaust instead of the intake.
Side note: someone before me put an Accel Super Coil on the top, but the special screws that attach it to the cap have a black oxide coating that was kinda rusty.
The "while I'm there" means new cap, coil, cover, wires, air filter, and breather filter (a GM thing)...

When I was a kid we did this thing where you would coast down in second gear with the key off then turn it back on as you got up next to a car. At night with header mufflers on it would make a large fireball under your car and one hell of a bang.🙂
This didn't work out so well for Thrush mufflers.