There are what look like transfer slots in the secondary barrels, should they be completely covered when the butterflies are closed or should they be partially exposed like in the primary barrels?

 

4 corner idle, or no?

 

Is 4 corner idle when it draws fuel from all four barrels for idle? I don't know if it is. It's a Holley 4160 list 80457 and I have an 80508 that has the same slots.

 

Doesn't really matter if it's four corner idle or not, because even two corner Holley's have a basic idle system ( non adjustable ) on the Secondary side.

The Secondary side is not as critical as the Primary side but the Secondary side butterflies should not be closed all the way, nor should the Transfer slots be exposed too much.

You can adjust the Secondary idle to get the Primary blades in the correct position re Transfer slots.

 

I called Holley and they said to back the screw out until the secondaries are completely closed and then turn it back in 1/4 turn, this is about .010 inches which is the spec.

 

Nothing like getting it from the horse's mouth (rather than the other end, as we know all too well... ).

 

This would be a basic starting point. The more camshaft duration your motor has the further you can open up the secondary throttle plates at idle. This lets the airflow be shared between the primary and secondary barrels at idle ensuring the primaries are not open too far ( with larger,low vacuum camshafts). This static setting would be for motors with very high vacuum at idle. (like with a stock cam)

 

That's a good point. The solution I've always heard for primary plates being open too far during idle is to drill small holes in them so you can back the idle screw out.

 

You can also install a PCV valve with a higher flow rate or run TWo PCV valves [one in each vlave cover, along with suitable vents] ( double the airflow), as well as open up the sicondaries a little. using these methods will get you where you want to be without drilling throttle plates even with a radical cam. The engine doesn't really care where it gets the extra air flow from. Nothing stopping you from making your own homebrewed "Idle Ease" (adjustable extra air bleed in the PCV)

 

Hmmm...I like that. Nice and simple, easily adjusted. :thumbs up: