Learned A Little Something New Today....

[A383Wing]

Yea..I know....I'm old....but this one kicked my ass for 2 days.....

We had a 69 Dodge D-200 in the shop for a new 318 engine...all went well until it was time to run it after install

Truck was converted from points to electronic ignition, has Mopar dist, and GM 4-pin HEI module mounted to firewall...(see below pic for module style)...on one side of module are 2 pins..both the same size pin..one is for 12v power, the other goes to ign coil...the other side of the module has 2 other pins...one is smaller than the other...these two tabs go to the 2 wire connector on the Mopar distributor's pick-up coil....

Here's what kicked me...evidently it makes a difference how the 2 wires connect to the dist....if you connect them up wrong...timing will be off by 20* at idle, and when you rev the engine, the mechanical advance will retard the timing instead of advance it....guess the AC voltage generated by the reluctor inside the dist has a reverse effect on the module if connected wrong. Not sure what made me think of changing the wires around, but truck runs great now.

We changed out distributors (twice) and even the intermediate shaft thinking something had slipped...

I always heard of using the GM module in place of the Mopar ECU, thought about trying it myself, still may, mainly because they are easier to come by and less expensive to purchase as opposed to the Mopar ECU's which most parts houses fail to carry anymore

I'm gonna try experimenting with the 2 wires on my cars to see if it makes any difference in the way the distributor wires are connected to see if timing is affected or not with the Mopar ECU's

I'm tired, my 3 brain cells are taxed out...fell free to laugh yer asses off at my expense....

Bryan

[440]

Good ol GM HEI.... Cheap, readily available and reliable.... If I remember correctly they have a plug that prevents plugging it in the wrong way... I suppose if you adapted it to Mopar you wouldn't have that plug though...

I did have one fail on me however in the Burger king drive through which was a fun experience...... Shut car off so I could hear and speak to place my order... she wouldn't restart... luckily I had an Accel one in the trunk that I purchased from Kohlweise that morning to put in during the weekend.... Didn't get on my way till just after 11PM

[nascarxx29]

Seen the HEI conversion before .Ever see this other EI upgrade
http://board.moparts.org/ubbthreads/showflat.php?Cat=0&Board=best&Number=1163204&Searchpage=1&Main=1162235&Words=+72roadrunner&topic=&Search=true

[A383Wing]

I then yanked out the handy dandy Moparts electronic distributor wiring, and looked closer at my harness. The harness I have has a brown wire and a black wire going from the 2 prong plug to the Orange ECU unit. The harness is wired exactly backwards from what the moparts diagram says it should be! The brown and black wires are not swapped, so I think it was wired this way from wherever the harness came from, which is no telling where.

I yanked the harness out of the car and peeled back the tape next to the two prong plug and swapped the wires, heatshrinking and soldering the connections. I then put the harness back in the car, and no double fire!

I then hooked up one of my tachs with a reproduction board in it, and the tach worked perfectly, reading the proper RPM everywhere.

kinda what I found also...he also mentioned about the firing on the "leading" edge of the reluctor as opposed to the "trailing" edge...which is what we were experiencing. Once I swapped the 2 wires around at the dist, engine ran and started as it should