Why am I running out of breath at 4-5000rpm

[blackened88lx]

Yeah, it might want a little more fuel. It seems a little lean.

 

[jrichker]

Got the AEM wideband installed today and went for a run. I'm idling at 11.6:1 and cruising around 12:1

On most WOT runs it starts off around 12:1 and moves up to around 13.6:1 at around 4500-5000 although I did see a 14.x once.

Would being a little lean up top cause it to stop revving?

Air/Fuel ratios:
perfect mixture for max economy and general driving=14.7:1
lean max power (best power) = 13.5:1
rich best power (extra fuel to cool the engine) = 12.5:1

The power valve increases the fuel at WOT. Check to see that it is operating properly.

See http://www.carbdford.com/ or http://www.jason.fletcher.net/default.htm for carb help.

I would look closely at the ignition side. A high speed miss due to poor ignition would be the prime suspect. Coil, plug wires and May Suddenly Die (MSD) box are the first places to check. Try bypassing the MSD box.

 

[C0V3R]

Also check to see that you are getting full throttle by looking down the carb while a buddy puts the peddle to the floor. Your secondaries might not be opening also.

Thanks for that! Turns out thats exactly what the problem was. The throttle had too much play in it so that it looked ok if adjusted from the engine bay but if someone trod on the throttle the play left the throttle 1/4 shut.

It now goes up to 6700 (before you run out of road) without blinking an eye!

Goes to show you should never overlook the obvious!

 

[olyfiveoh]

I would suspect the the cam. Not sure about the specs on your cam, but one that will delay the intake valve closing will increase flow at top end.

 

[Sicarius428]

That cam is good up to 6500rpm +. TFS stuff may lack a little low end but really comes in 2500 on up.
Kevin