OPEN 9:00 to 5:00 PM EST (Mon-Fri)

Casper's Electronics 109039 86/87 GN TO HOLLEY ENGINE HARNESS
Casper's Electronics 109039 86/87 GN TO HOLLEY ENGINE HARNESS
  • SKU: 091-109039

Casper's Electronics 109039 86/87 GN TO HOLLEY ENGINE HARNESS

Shipping calculated at checkout.

CASPER'S ELECTRONICS has made several thousand engine control harnesses for the Grand National since our first one in 1996.  From stock ECU's, and right down the line of all the aftermarket ECU's, the next installment is our new Holley to GN engine control harness.  We’ve taken the most requested features and included them across the board in all of these harnesses.  With a strong focus on upgradability and reliability down the line, much of this harness is modular allowing upgrades over time by simply plugging in the appropriate harness.  

Casper's Electronics has been providing the highest quality components for the Turbo Buicks since 1988, celebrating 35 years of providing parts to the Buick community!  CASPER’S has a robust distribution network for our parts with many value-added suppliers.  Check with your favorite parts supplier to see what bundles they have to offer!  Or, drop us a line!  We’d be happy to point you in the right direction.  

A few features of the BASE harness…  

* 2 MAP LOCATIONS - factory location to utilize factory boost/tach module - second located at the back of the intake which feeds the ECU 

* 70A FUEL PUMP FEED- easy plug and play upgrade to your fuel pump with 8 gauge wire.

* UNIVERSAL COIL CONNECTOR - Use smart coils, truck coils, original CCCI, or any future options - completely plug-n-play.

* BATTERY CABLES / POWER DISTRIBUTION - Included with all harnesses including appropriate fusible links and ground straps. 

* FAN CONNECTION - Available and driven by 40A relay. 

* CAN BUS - Under dash and under hood. 

* ALTERNATOR FIELD FIX - Built in. Keep that alternator charging!

* AUX CONNECTOR - With Inputs/Outputs, including sensor return, +5V, switched 12V, constant 12v and ground available, add auxiliary connections under hood without cutting or splicing.  

* FACTORY INTEGRATION - If you use the factory CCCI, your factory tach will work.  If you use the factory MAP, your boost gauge will work (analog dash cars).

* POWERMASTER - Feeds for powermaster on all harnesses.  

* A/C - Included on all harnesses.

* FUEL / OIL PRESSURE - Connectors included on all harnesses. 

* SEALED RELAY BOX and FUSE HOLDER - 3 x 40A relays, 1 x 70A fuel pump relay - corresponding fuses for application.

How to order this harness:

BASE HARNESS - These are all exactly the same.  It will come with everything outlined above.  Next, you will choose what coils and injectors you are running.

COIL HARNESS - One is included in the base harness price.  If you choose to upgrade later, it will be 100% plug and play.  Choose ONE of the following... 

  • Stock CCCI
  • Holley Smart Coil (5 wire)
  • LS Coil (4 wire)
  • Request special coil configuration

INJECTOR HARNESS - One is included in the base harness price.  If you choose to upgrade later, it will be 100% plug and play.  Choose ONE of the following....

  • EV1 Injectors (same as stock GN harness)
  • EV6 (USCAR) Injectors
  • DENSO Injectors
  • Request special injector connectors


  • 8 AWG 70A Fuel Pump Hotwire Kit
  • FlexFuel Kit
  • Boost Control Kit
  • Holley E-Dash Plug-n-play harness
  • Coil mounting brackets for Holley Smart coils or LS coils in factory location
  • Request a new integration

ALL the harnesses listed above are built to the highest standards, ensuring correct operation from the get go and the reliability you’d expect from an OEM harness.  All wire used on these harnesses is automotive spec 125*C rated, brand new, crosslinked TXL and SXL wire cut by machine.  All terminations are done by press and continual in-process inspection occurs throughout production.   All harnesses are electronically inspected for point-to-point continuity as well as resistance and serial numbered before they leave our facility.  This is the benefit of decades of experience building engine control harnesses.  The same production lines and equipment we use to build harnesses as a Tier1 supplier to the OEM’s are used to produce these exact harnesses.

Contact Us Now to Speak with one of our Professionals in High Performance!
PHONE: (586) 294-4404
FACEBOOK: @FullThrottleSpeed
E-MAIL: steve@fullthrottlespeed.com