Our newly purchased 1977 D800 with air brakes has a Holley 4150G on it. I have rebuilt it using the manuals and quite a few tips gathered online. The missing piece of the puzzle is how to tune this beast. The factory configuration of the various components is unlike any other Holley I have worked on.

First, the idle mixture screws are on the secondary side. Supposedly the governor magically controls the primary idle mixture per the Holley manual. There is an idle speed set screw (no idle mixture screws) on the primary side and I set it @ .020 exposed transfer slot along with the secondary.

Also of note is the distributor on this setup. It is and electronic tach drive deal with vacuum lines going to and from the carb. One vacuum line is connected to ported vacuum and the other goes to the governor dashpot.

With all of that said, is there any reason why I can't put a non-governed carburetor in the 4150g's place with a regular distributor? Being a '77 with electronic ignition the distributor is plug and play.

For what it's worth here is how I have it setup:

Primary:

-no idle mixture screws)
-64 jet (factory was 58? never had a jet that small in anything)
-Two stage PV, acted like a 1"-10" when tested

Secondary:

-idle mixture screws 1.5 turns out
-76 jet (was a 74)
-no PV


I'd sure appreciate any insight on this situation. It's getting harder and harder to find a mechanic that worked on stuff like this.