Let's look at another variation of a performance ignition system upgrade.
This system is now installed on a '73 t'all with performance built 392 (9.0:1 cr and cam) described in this thread:
http://www.forums.IHPartsAmerica.com/readers-rides/4072-dd-known-chunk.html
As seen in that thread, the major drivability issue was created when the engine was "professionally" rebuilt because an attempt was made to retain the entire oem emissions system including the carburetion and ignition system. That simply won't work and I have no doubt that is why the vehicle was parked after acquiring 3,000 miles of runtime over 20 years ago!
I've now taken care of the fuel system issues and a carburetor has been installed that is adequate for the engine spec though the final dial-in has yet to be done.
That leaves the ignition system needing attention. So what I've done here is typical of our ihon members who are looking at performing an ignition system upgrade but have a budget to work within. And that starts with the distributor.
So...in this case I'm going to leave the breaker point-equipped distributor alone initially. Again, typical of what most of our customers face. This Holley distributor was replaced with an a-1 cardone reman unit at the time the engine was built, so it's as fresh as can be. The dwell has been set to 30* and base timing performed. The distributor has an oem advance curve suitable for egr...so that also has been left alone. All we're going to do here is add an aftermarket capacitive discharge box and a matching coil to the breaker point distributor.
By incorporating the cd box into the ignition system, the current across the breaker points becomes almost nil, that in turn adds greatly to the life expectancy of any breaker point set. The deciding factor regarding point life then becomes wear on the rubbing block, these points are now capable of running 50k miles if the point cam is kept lubricated.
So the system as you see it here consists of a Holley point distributor (stock), a new prestolite distributor cap with male terminals (modded to properly install on the Holley distributor body), msd helical-wound plug cables (8mm od insulation), an msd blaster ss "e" core ignition coil that matches the output characteristics of the cd box, and an msd 6a capacitive discharge box.
The msd box is virtually identical in operation and performance to the mallory 6 box described in the earlier posts. I have no preference for one over the other, the "digital vs. Analog" stuff doesn't make a shit to me! In fact, msd actually buys the mallory digital box and re-labels it under their own brand! Likewise...a "rev limiter" feature is certainly useless on an IH tractor motor (even a built one).
The add-on auxiliary fuse/distribution panel is not part of the system, that is simply a convenience point for adding in additional vehicle system loads to the battery. The two circuit breakers seen in that panel are for the electric trailer brake controller and for protecting the charging line that feeds the trailer (dual batteries) also. In the future...a sound system might be added to the mix, an underhood work light, and an auxiliary b+ power connector.
The msd box incorporates internal circuit protection and should not be connected to a fused b+ power source. In this case, b+ for the box is simply taken right off the additional battery feed to the fuse block. The msd box harness is then grounded right to the inner fender which has been properly cleaned and bonded to the negative side of the battery/charging system.
The oem coil/mount was simply removed intact and stored in the truck box for an emergency backup in case the msd system ever fails. The oem coil wiring connectors (including the "resistor" wire) were insulated and taped back into the loom also where they are easily accessible. No oem wiring is used with this system other than the distributor breaker point wire run that connects to the msd box. Everything about this wiring work is easily reversible on the side of the road if need be.
