Any hints on tuning for a big cam?

[Tom Sharpe]

Bruce Plecan wrote:

> IAC motor trimmer?.  Can I ask for you to expand on that?.
> What for IAC count do you run at idle
> Bruce
>
> >Mine's about 20% rich at idle with 10 deg retard from normal. the iac
> >motor trimmer is also at minimum to reduce the hunting.    Tom S

It's an Edelbrock adjustment factor - set from the calibration module. "When
the Idle Control is ON, the ECU will try to keep the engine running at the
Target Idle RPM. As the RPM at idle deviates from the Target, the ECU will
respond by changing the air flow through the IAS. ( Ford IAC) The Idel Speed
Activity factor is one parameter that the ECU uses to determine how much to
change the air flow. if the factor is too low, the system will be slow to
respond to changes in idle speed. If the factor is too large, the system will
overcompensate causing the engine to surge or rapidly hunt up and down for
the correct idle speed."

Allowable values are +-50% in 10% increments. "Normal" idle for big cams is
rich (but not enough) and advanced. My engine has 10.5 CR (measured), 0.000
deck, and 236 deg @ .050 (Hydraulic) with 106 centers in a 6" rod 406 SBC.
The result is 13' vacuum at 950 rpm and 17 at 1100, and enough throttle
response to pull the wheels. The blower roll (surge) at idle was so violent,
it would spin the tires and leap forward with both feet on the 4 whl. disk
brakes.

I made it very rich, it has 28 lb. inj. with 50 psi delta (intake vacuum
compensated regulator) and 5 ms pulse at idle. It loads up at 6 ms and idles
rough at 4 ms. The spark is retarded to about 20 deg at idle.  It's not a
puppy, but my wife can drive it now.  The 5 ms pulse is about the same at 70
mph cruse (2500 rpm).    Tom S