Huge backfire, no start

[1978911sc]

She’s a 1978 SC. Recently had the top end redone. All new gaskets, seals, and hoses. Took her out for a drive. Ran great for an hour and half. Didn’t really push her that hard at all. Came into a corner, slowed, downshifted and all of a sudden lost all power. She backfired loudly and died. Now she wont start. Turns over just fine, but nothing.

Anyone have any thoughts on where to start looking?

Thanks in advance.

[john walker's workshop]

Take the air filter cover off and see if the pop-off valve popped out. If there is one. Then check if the top and bottom of the plastic intake airbox separated at the seam. If you see any screws out or 1/2 way out, that's an indication.

[boyt911sc]

Your airbox has been compromised. You need to do a smoke test to locate and identify the source of your unmetered air.

Tony

[Joe Bob]

If you had a professional wrench do your top end and he/she didn't install a or off valve or inspect your air box, feel free to go out and slap the crap out of them...

[pmax]

Originally Posted by Joe Bob

If you had a professional wrench do your top end and he/she didn't install a or off valve or inspect your air box, feel free to go out and slap the crap out of them...

Yep.

I assume "All new gaskets, seals, and hoses" means soup to nuts.

[john walker's workshop]

Split airboxes can be a fire hazard if you keep trying to start the engine with the cold start injector spraying fuel.

[mike sampsel]

If it's not your airbox, check the plug-in to your CDI box. I had a similar experience (loud back fire, quit running, no start) until I got the loose plug in tight.

[pampadori]

That's how my car grew internal throttle bodies.