Ignition control module

[NMNorsse]

Circling back to the 9c1 police pursuit spec ICM (D1943A) the Delco OEM one is $115 at O'Reillys and $75 from Amazon.

EDIT- RockAuto has a Standard Motor brand one for about $20 + shipping. Standard Motor is good brand.

Off topic, the 9C1 police spec TBI injectors, which flow at 68 gph versus the OEM 55 gph on a 5.7 are like $200 each new from Delco. RockAuto has some remanufactured
ones by GB for $27 plus shipping and $30 core. Supposedly you can upgrade to the 9C1 injectors without changing the PROM or programming. That may be true, but I would guess that datalogging and making some adjustments would be better.

 

[Schurkey]

My 96 truck

Circling back to the 9c1 police pursuit spec ICM (D1943A) the Delco OEM one is $115 at O'Reillys and $75 from Amazon.

Which is fine...for a TBI vehicle. The '96-newer Vortec engines that have a distributor use a totally different module.

History of HEI ignition modules:
1974 (select applications) and '75 (all domestic) to the end of the non-computer era used a 4-pin module that's still popular with hot-rodders. The module grounded through a mounting screw, so there's 5 electrically-important contact points.

Early knock-sensor vehicles had one of two 5-pin module designs; the fifth pin retarded timing when supplied with a signal: + voltage (one design) or was grounded (the other design.) Module ground was through a mounting screw, for six electrically-important contact points.

Early computer-controlled vehicles had 7-pin modules, grounding through a screw for eight electrically-important contacts. I have a book--somewhere--that details the '77--78 Olds MISAR-HEI system. I don't remember what module that used.

Later (TBI) computer-controlled vehicles used an 8-pin module. Again with a screw as a ground. Nine electrically-important contacts.

96-newer "Vortec" engines with distributors went back to a 4-pin module of different physical design, and with different functions for the pins, remote mounted on a dedicated heat sink outside the distributor body (in part because the distributor body was now crappy non-conductive plastic instead of God's own aluminum.) The module is grounded via one of the pins, so only four electrically-important contact points.

I have seen pictures of an "HEI" module with only three pins. So far as I can tell, this was used only on European vehicles; a cost-cut "knockoff" of the true HEI system without the full HEI features such as variable dwell. I've never seen one of these modules in real life.