Replaced a cracked header & now it backfires

Yea, I'm stumped too. I get that it might be a timing issue, and timing is adjusted by the ECU based on the sensors input. I've also read that backfiring thru the intake is a lean fuel condition.
All I can think is to take it apart again. But what would I be looking for?
 
I don't know what to tell you to look for but yes taking back apart might help you figure out what or why it's doing this. Becasue it only started after you'd replaced the exhaust header I'd say something happened during reassembly. Maybe as you start taking back apart you'll find something you missed or where a wire or hose got pinched?
 
Airjunky said:
A buddy of mine suggested maybe a valve bent recently. The backfiring would be compression coming through.
Click to expand...

While stuff can happen unexpectedly when doing other work I'd guess it's pretty rare so I'd be looking at what you removed and installed when you did the exhaust before I'd be chasing other issues.
 
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Went to O'reilly's today & borrowed their fuel pressure gauge. I did it twice, and it showed I had no fuel pressure..... zero. Even when I pushed the pin on the Schrader valve, I just got a few little drips out.
I don't get how, if I really have no fuel pressure, that the damn thing runs at all.
I'm going to check the gauge on my Chevy Avalanche & make sure it works right. There is no o-ring inside the cap or the pressure gauge cap.
 
So the fuel pressure gauge from O'reilly's proved to be inaccurate. I have around 49 psi of fuel pressure.
At that point I figured it was time to remove the intake and exhaust that I had installed and started this mess. I'm pretty good at it by now so I had it done pretty quickly. And found nothing.
So next we decided to do a leak down test. We had done a compression test earlier and found each cylinder between 125 - 132 psi. The leak down isolated the problem to cylinder number 5. We manually turned the crank and the #5 exhaust stroke was leaking badly. Pulled the valve cover and sure enough, one of the cylinder #5 rocker arms was limp. Pulled the head and found out why......

KIMG0660.JPG
 
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