General AFR Guidance (Holley Tuning)
Does anyone know if there is an accurate chart available that shows the difference in accelerator pump cams? I found a few online, but they all seem different.
One reason they vary is that there are several possible pump levers, so it depends on the carb. Also the contact point of the arm can be alterered - in fact it often has to be when changing pump cams. There may be other reasons too.
That said: This one is a copy of the one from the Holley catalog (and I've had Holley tech e-mail me the same)
http://racingfuelsystems.myfunforum.org/Holley_Pump_Cam_Chart_about16.html
a Chart version from Holley posted here
http://racingfuelsystems.myfunforum.org/viewtopic.php?f=25&t=754
Another on a 4150 in this threads
http://racingfuelsystems.myfunforum.org/viewtopic.php?f=25&t=642
Another thing I noticed is that cruising at a constant 2000-2,500, AFR is around 14 and WOT is at 15.
That seems like the PV wasn't opening or the rpms were low or the load was light. Full load, full throttle should have dropped AFR into 12-13 range. It might not show on the meter immediately but should for the bulk of the pull or run.
I'm guessing it would be wise to tune the pump shot and idle first, then work on cruise and WOT.
Idle, off-idle first and hold off on pump shot as long as you can stand it. Should be able to slowly and gently open throttle from idle with no stumble. Once the mains are fully flowing, somewheres near 60 mph for most dependng on setup, no pump shot should be needed (primary side or vac secondary carb). Personally, I get frustrated with the stumble 'cause I'm testing on the street; and if you do too, just put more shot into it knowing you'll rework it once the idle, idle-off idle is sweet.
In theory its best to work steady state tuning from idle, transfer and then main circuit. Then do the WOT. This is because the the idle/transfer systems take from the main well. The transfer slot also can contribute air back into the main circuits at WOT. However personally, I don't see an issue getting WOT once the idle/transfer is pretty close. I feel safer jetting and making any air bleed changes for the WOT runs, at least on the primaries, then coming back and seeing if the high speed driving (65 mph, 3000ish rpm) can tollerate leaner main jets. If so,then the PVCR will need to be increased (Holley). If not, then move onto secondaries and fine tweak the pump shot.
