A/F readings

[FLYBYU]

Would a cracked header change my A/F readings. I'm running at about 75 mph at 7500 rpm and A/F reading is going between 10.8 to 11.1. Cpr header with 2871 turbo, excell exhaust. When it starts cold it sounds like a little ticking noise but it goes away when it warms up. Any ideas before another teardown

 

[Turk]

I had 2 cracked headers. They will usually show a drop in boost on a long pull.
None of mine made any noise; just slowly dropped 2-4 pounds boost after 3-400'.
I never noticed a change in a/f ratio but not saying iit,s not possible.

 

[wienerwater]

We talked about this before, in my case, loose header bolts. It would make a difference, since with the turbo spinning, you would get a vacuum effect through the crack, or any open source, causing extra fresh air entering the system. It would show a bit leaner, more air being measured off the sensor.
In my case, it was a ticking when I let it sit for maybe 10 minutes after a ride, then restarted it.After maybe 20 seconds, things would expand and seal it a bit, ticking seemed gone.I assumed the leak, and had 4 loose header bolts. Fixed and A/F less erratic and realistic now.

 

[fullthrottle800]

Not sure but my FJO A/F gauge shows --- today not happy at all.

 

[chrisinparts]

same thing just happen to mine. took it apart and 3 header bolt backed out. put new ones in and all is fine.

 

[FLYBYU]

and so the tank comes off again