MP electronic ignition conversion kit

[zhandfull]

What is the difference between the new ballast they supply with the kit and the old ballast on the points type cars.

I'm converting this 72 Dart from slant 6 and points to V8 and electronic ignition. I have an orange box and wiring harness. Thinking about using those two items along with a factory stock 1974 318 electronic distributor. Don't have the ballast can I get one from local auto parts store? Part number?

 

[BillGrissom]

Yes, but you need to know if your orange box has 4 or 5 active pins. Measure the resistance from pin 5 to ground. If infinity, it is a dummy. Some later ECU's didn't even have a 5th pin. If a 4-pin ECU (most after-market ones are now), you need just a single ballast resistor (for the coil). I think it is 0.5 ohm for both electronic ignition or points, but could be different PN's. The 5-pin ECU's need the dual ballst (4 terminals), where the 2nd resistor is 5 ohm to protect the ECU itself. I think that was only the earliest ECU's, but rockauto is unclear - showing both single and dual ballasts for all 70-76 cars.

To add more confusion, some coils had internal ballast, so don't need a ballast resistor. I have one labelled "for use with electronic ignition" that I recall taking off a 1980's Ram Van. I am currently trying it on my 65 Newport (w/ electronic ign) without a ballast, and so far I haven't noticed the coil getting too hot, so I expect it has internal ballast. It measured ~2.5 ohm, but hard to measure so low. It appears that most after-market coils today are labelled "for use with external ballast" if they require one.

 

[zhandfull]

Sorry missed your post till now. I have the 4 post orange box.

The car still has the stock slant 6 ballast resister. In the past when I have done electronic ignition conversions. The kits always supplied a new replacement resister. However this little project, I'm doing with some spare parts that have been laying around. So I was concerned about if the 72 Dart slant 6 stock resister would work or if it needed changing. Car is now 318 with factory electronic ignition distributor out of a 74 Valiant and MP orange box and harness. Car starts and runs fine right now, just hate to burn something up.

 

[BillGrissom]

Should be fine. I would think if anything the original points ballast would have more resistance. If it won't harm points, it sure won't harm the ECU, nor the original coil. Measure the voltage difference from BATT- to coil+ and compare to the spec for a 74 car (~8 V?). If you don't exceed that, it should be fine.