Engine Gurus Needed

[84 Silverado]

Question for the Engine Guru’s:
1980-1985 corvette 350 in my 84' Silverado was running like a sewing machine. I have no information about the engine other than that. About a week earlier, I swapped the Q-jet for an Edelbrock 1406, I used a vacuum gauge to tune it to the highest vacuum, played with the 2 air and fuel screws to get the best idle, the timing was dead on. I set the fast idle to come on and pull off in about 3 minutes and all was good and it ran great. Fast forward 2 weeks and I’m cruzin’ around town doing errands and I stopped to drop off some dead batteries at the local police station, completing that errand, I fire up the car drove about 100 feet to get back to the street and BAM!!! The loudest backfire I’ve ever heard happens, I mean it sounded like a 7MM Mag rifle shot. Needless to say, I was trippin’ as I was still in the Police parking lot.
After a couple of seconds of cranking, the engine fired up and I drove home. Pulled into the garage, popped the hood and it sounded like the valves on the drivers side were clicking. As I had never set the valve lash in this engine, I pulled both valve covers and set the lash at 0 on all of them, reinstalled the valve covers. When I fired it up this time, the passenger side of the engine was knocking like nobody’s business. It was not the rocker clicking like before, this sounds like a real knock, like bad metal hitting metal knock.
I’ve been messing around with these cars forever but I’ve never come across this before. I’m hoping that I just missed something and ya’ll catch my mistake. But I can’t explain why the gnarly backfire happened, then the rockers start clicking. I feel like the backfire and valve noise are connected, but again, this is way out of my engine knowledge.
If you need more information to trouble shoot this please let me know.

Thanks in advance!

 

[Tank6x2]

Maybe pre detonation? Pull plugs - keep it simple, look for a plug that got way to hot.

 

[Ricko1966]

What was your procedure for setting lash?

 

[PrairieDrifter]

Usually big backfires out the exhaust like that is an exhaust leak. Have you looked at your mufflers since the bang? May be exploded. Possibly a vacuum leak, especially since you have been doin work up top.

I am also curious of your valve adjustment procedure.

Hate to laugh at the situation, but having experienced one of those backfires(kinda) I was a couple blocks away and I wasn't driving lolol.

But I'll be damned if I didn't cackle out loud at that story In the police parking lot no less lolol you'll never forget that story

 

[87scotty]

Dizzy didn't spin on you correct?

 

[SirRobyn0]

Question for the Engine Guru’s:
1980-1985 corvette 350 in my 84' Silverado was running like a sewing machine. I have no information about the engine other than that. About a week earlier, I swapped the Q-jet for an Edelbrock 1406, I used a vacuum gauge to tune it to the highest vacuum, played with the 2 air and fuel screws to get the best idle, the timing was dead on. I set the fast idle to come on and pull off in about 3 minutes and all was good and it ran great. Fast forward 2 weeks and I’m cruzin’ around town doing errands and I stopped to drop off some dead batteries at the local police station, completing that errand, I fire up the car drove about 100 feet to get back to the street and BAM!!! The loudest backfire I’ve ever heard happens, I mean it sounded like a 7MM Mag rifle shot. Needless to say, I was trippin’ as I was still in the Police parking lot.
After a couple of seconds of cranking, the engine fired up and I drove home. Pulled into the garage, popped the hood and it sounded like the valves on the drivers side were clicking. As I had never set the valve lash in this engine, I pulled both valve covers and set the lash at 0 on all of them, reinstalled the valve covers. When I fired it up this time, the passenger side of the engine was knocking like nobody’s business. It was not the rocker clicking like before, this sounds like a real knock, like bad metal hitting metal knock.
I’ve been messing around with these cars forever but I’ve never come across this before. I’m hoping that I just missed something and ya’ll catch my mistake. But I can’t explain why the gnarly backfire happened, then the rockers start clicking. I feel like the backfire and valve noise are connected, but again, this is way out of my engine knowledge.
If you need more information to trouble shoot this please let me know.

Thanks in advance!

All any of us can do is throw out ideas and guess. If you could take some audio record or video of the noise and post it so we can hear it that would helps us help you.