750 vs 850 vs 950 Holley

nm9stheham said
Interesting.... What do you guys think causes this? Maybe too much air above the emulsion holes? (Oops the idles may not have a real 'tube'..)Or something unstable in the airstream higher up? Just curious....

The higher locations allows air to get on the other side of the IFR when manifold vac is low enough.

skrews said
I don't know what the reasoning is behind the high IFR. Part of me thinks its just monkey see monkey do engineering.

Does seem that way. I've seen a few of these builders occassionaly post explanations. Maybe I'll find them and start a thread just on that.

yellow rose said
I have one of the queer applications because every time I lower the IFR the car doesn't idle nearly as well. I have spent enough time on it that I gave up and moved them back up and let it go. Everyone I know moves them down, but for whatever reason, mine want to be up.

One use of a high idle position is providing a shot of extra fuel from the idle up-well. When the throttle is opened wide flow changes direction and goes from the idle upwell into the mainwell. This seems to be the reason secondary metering plates have the restriction up high. Maybe you have a situation where that extra shot is just what is needed. Mark Whitner's mentioned this, and Tuner explains it in post #23 here: Secondary metering plate vs Secondary Metering Block?

edit: Mark mentions it here, but in reference to the emulsion well.