Sudden backfire and won't start until I adjust AFR
 

So, I go to start my 454 with an Edelbrock 750 on it and it doesn't start...the starter hangs up like it's too advanced and backfires through the carb. I adjust the carb mixture a bit richer and it starts up and runs a bit shakier than usual, but still drives fine.

I get home, adjust the idle mixture again and the shake is gone and it runs fine, just like normal.

Should I be worried or no?

Re: Sudden backfire and won't start until I adjust AFR
 

What do you mean by 'adjust the carb mixture'?
If you mean the mixture screws, those are only for idle.
Was the motor cold or hot when you started it?

Re: Sudden backfire and won't start until I adjust AFR
 

I had to adjust the idle mixture to make it start and run.

It was in the middle. It had been sitting for at least 30 minutes, if not more.

Re: Sudden backfire and won't start until I adjust AFR
 

Now you got me confused!
Adjusting mix screws shouldn't change starting.

What was 'in the middle'?

What's your initial timing?

Re: Sudden backfire and won't start until I adjust AFR
 

I know! That's why I don't think it jumped timing or anything.

The motor wasn't warmed up or totally cooled down, so it was "in the middle" per se.

16*

Re: Sudden backfire and won't start until I adjust AFR
 

Pop the dizzy cap and check the weights aren't hung up.
Did you check your timing?

Re: Sudden backfire and won't start until I adjust AFR
 

Didn't check my timing today, but it was retimed in the past 2 months

Re: Sudden backfire and won't start until I adjust AFR
 

Lean and retarded makes backfires!
Perhaps the fuel was all boiled out of your carb from heat and contributed to the backfire.
Do you have a heat plate under your carb?

Re: Sudden backfire and won't start until I adjust AFR
 

I have a half-inch wooden carb spacer.

I figured it could have been the fuel boil. I just wanted to make sure my motor wasn't about to **** itself or anything.

Re: Sudden backfire and won't start until I adjust AFR
 

Coulda been a one time thing.
I had a bbf 460 that coughed every time it started.
If it does it again just look in the carb venturi first to see if you have any fuel.