CDI+ Install notes for an early G-body with an SC 3.0 motor

[Michael D]

This is a brief description of a two stage process brought about by the failing MSDS (Red Box) plus Blue coil solution.

The fix I sought was to address the tendency of the motor to run rich and be sluggish over 3000 rpm.

C.I.S was already replaced by PMO 40mm carbs and emissions ancillaries plus aircon were removed at the same time.

Stage 1: Plug and play replacement  using 6-pin CDI+ and new harness which included new Green-wire connection for breaker-less distributor. The early G-bodies do not have the Tacho (purple on black) wire terminated in the 14-way connector, but the stock vehicle harness presents a two-way connection with tacho and ignition switch in the same location as CDI is mounted. The coil was replaced by a Black version. The new 6-pin harness was not strictly necessary, but made for a tidier solution. Stage one established that the install worked and ensured that static timing and idle were correct ( 7 BTDC at 870 rpm ).

Stage 2: Preliminary testing of the distributor over the desired rev range indicated that although the built-in spring / weight arrangement had been changed from stock (C.I.S), the new advance curve did not get much above 20 BTDC and could not rev easily above 4500rpm. PMO tech support advised up to 35 degrees total advance. Using the internal advance capabilities, I worked my way up to a curved giving 34 degrees total advance by 3000 rpm and the motor revs easily to 6000 rpm now.

In the process of installing the advanced features of the CDI+ I discovered that the non-racing version of the computer link  has rather fragile conductors and so inserting the connector too firmly does run the risk of  damaging at least one conductor if too great a force is employed when removing the link cable from the CDI+. 

Also, if the two flying leads for shift light and launch control are unused, they should be completely insulated and taped out of harms way to avoid accidental grounding.

All that remains now, is to do get some dyno time to check the power output and AFR to see if there's any room for improvement in the mixture settings and Advance curve.

Otherwise , I am very content with the resulting performance improvements.

Michael D

Edited June 11 by Michael D
added details