[Tom Vaught]

Going to slowly get back up to speed on the posts by starting with a short one this morning, Hope everyone had a great Christmas Holiday.

Today I will talk a bit about the emulsion circuit (in general) and the high location IFR (Idle Feed Restriction) vs the historical low location IFR (Idle Feed Restriction).

The picture I have posted shows a "5 hole" Emulsion design, a upper Idle Feed Restriction, a lower Idle Feed restriction (Historical position) and the Angle Channel for the Main Metering Circuit.

1) The picture suggests:
a) Open up the Angle Channel to .160" drill size.
(This adds more fuel flow capability to the carb boosters, as easier to pull fuel thru a larger channel quickly.)

b) Drill out or unscrew the Holley "Upper Idle Feed Restriction". This will allow the reversal back to the "Lower Idle Feed Restriction" location. That mod was ALWAYS a bad idea.

c) Install a new "Lower Idle Feed Restriction" like the Holleys had for many years that worked great. Lots of idle instability with the High Mount Position IFRs.

The HP Metering Block shows the 5 Hole Emulsion capability which works ok with vast amounts of Dyno time on a NASCAR High RPM Race Mode vs Yellow Flag Fuel Economy Parade Lap Mode calibration.

Most tuners block the #2 and the #4 Emulsion Holes on Drag Race type carbs. Some even block the bottom #5 hole. Some think that it helps at the very top of the MPH curve. Most would see little benefit vs the old 3310 and 4781 List Number TWO HOLE Emulsion Circuit with calibrated holes at the #1 and #3 positions.

So the HP Metering Blocks can be FIXED if you spend time putting them back to what the old metering blocks Emulsions positions were and move the IFR back to the lower position. JMARKAUTO, TUNER, Shaker455, (All excellent Tuners), Myself, and others do this "reverse mod" often.

Unless you have access to a lot of Dyno Time don't mess with the Emulsion Circuit and instead just use the design from Holley had for years that worked very well on the Older carbs.

Tom V.