Holley HP install and tips

Sean Krupa

I run -8 feed -6 Return lines. Dual 340 pumps. Used to run 120lbers but wanted extra room for future so I moved up to 160s. I also maxed a Single Walbro 450 pump running mid 10s. Now I'm 10.2 Best so have plenty of fuel now.


So I don't see anything regarding using the stock distributor. I bought the GM Small Cap harness. It is my understanding that the white wire is tach signal to the dash. What I don't get, is how the coil gets set up. Anyone know?

Here is my thought, Using the Holley white wire labeled (points) to the harness white of the coil, power from 12v to the coil harness, should that be it? What happens when MSD is in the mix?? I have heard from Holley and Scott that MSD is not needed but I would be nervous to run the stock distributor running meth and a 76mm turbo at 25+ psi.

randy merritt

Donating Member
The Holley harness plugs into the stock distributor. It does not attach to the coil. I did not use the white wire at all. In fact, I think that Tyson fried his Holley by using the white wire.


So you're saying don't use the white wire from the main harness? Interesting, Holley told me to. So for the coil, do you just use a 12v source? Also, what about the MSD?

randy merritt

Donating Member
From my first post:

Loose wires:

Red with fuse - battery positive
Black - battery negative
Red/White - switched positive. I think I ran mine to the fuse box
Green - fuel pump. Either directly to fuel pump (if amp load is not to high), or trigger the stock or aftermarket fuel pump solenoid. This wire is capable of directly powering a stock or Walbro 255.
White - NOT USED
Yellow - NOT USED

randy merritt

Donating Member
My post disappeared, but no, you do not use the white wire. Look at my very first post in this thread. The coil just plugs back onto the stock connectors.

randy merritt

Donating Member
I'm going to write this down before I forget. I just had to relearn it again.


The evaporator pressure switch has two wires. The light green wire (input) comes directly from the a/c controls. The dark green (output) then goes to the factory a/c compressor control relay where it is controlled by the stock ECU. It turns the a/c on or off for certain engine conditions (WOT for example). In order to make it work without the stock ECU, take the dark green output and run it directly to the compressor clutch. The compressor clutch has two wires. The dark green, which we now have coming directly from the pressure switch, and a black ground wire.

A junk yard vehicle can supply the needed fittings as another option so you don't have to cut any stock wires. Find a female connector that plugs into the stock connector as shown in the pic (standard S10 stuff).


grab a pigtail going to your compressor clutch (make sure you get the right style of connector, they differ), and splice the two together. One wire for clutch, the other is clutch ground that goes to the factory ground location. No need to make a new ground.



Old Guard GURU
Got a lot done the past few weeks I'll be brief as most of this has already been covered...

I will definitely go more in-depth on the MSD box because I am still using mine.20200515_133822.jpg
Holley wiring is so small that I decided to solder the new connectors on.


Gear Grabber
Just to clear up, after reading through this thread is this everything that's needed to get one of these rolling on Dominator/HP? (ECU not included in list)

Universal MPFI Main Harness

Main Power Harness

HEI GM Small Cap Ignition Harness

Universal 6 Cylinder Injector Harness

LSU4 Bosch Wideband

3 Bar MAP