Jacobs Ignition Installation

Contributed By: John Jacobs

Well, I got my Jacobs Ignition System in the mail last week and installed it yesterday. I purchased the Omni Magnum Team with Ultra-fit plug wires (Part Number 361897) package, and paid about $400. I have a 1975 Jeep Wagoneer with a 360 V8 and the BID distributor system (an early AMC attempt at HEI.) I am using the stock coil, distributor and cap. I installed new basic Champion plugs gapped to their recommended .052" (yeah, it does seem like a lot.) The system comes with three basic pieces: the Omni-Magnum main unit, Secondary Trigger, and the new plug wires. The package also comes with all of the necessary mounting hardware.

The first step was to figure out where to put the main unit. The main unit is about 4" in length, 4" high, with a width of 5" at the base and 3.5" on top. It took a while to find a place, but I decided to go with the front wall on the driver's side. It is mounted between the radiator and the light. There is just enough room in there. I also chose this place because it allowed me to run the power leads to the battery by running them with headlamp wiring harness running in front of the radiator. To install the unit I marked my pilots, drilled 'em, then used the supplied self-tapping screws to attach the unit.

I then installed the secondary trigger on the driver's side wheel well using the same tactic. The secondary unit is approximately 5.25" x 2" x 1" (l x w x h) and also mounts with the self-tapping screws included.

Next was the wiring, which was not hard at all. I hooked the lead from the main unit to the distributor, and the lead from the secondary unit to my stock coil. I also changed my plugs and wires at this time. Then I took the power leads and ran them to the battery, following the wiring harness for the headlamps. Since the power leads aren't the longest I snaked them up the passenger side of the radiator harness and hooked them up to the battery. I taped and zipped-tied them *real* good too keep them from rubbing or touching something warm. Finally, I installed the included 15amp fuse.

The system was now ready to go. I re-checked the connections then hopped in the cab. First crank and it started, all right!! I hooked up the timing light and set it to 5 degrees BTDC. I took it out for a test spin and it seemed real good.. but-- when I really got in the throttle it started knocking like nobody's business. So I moved the timing back to 2.5 degrees BTDC (stock) and took it out again. Same thing, only not as noticeable. I was kind of bummed by this, but it was late and I didn't have time to tinker with it anymore.

I also should note that this was also present with the stock ignition system. I believe the knocking is due over-advance with the vacuum on the distributor. I am going to re-do all of the vacuum hoses and see if this helps. If not, maybe close the gap on the plugs a little.

As a final note, I came home from work today and decided to see how the Wag started in the rain (60s and steady rain today). It started on the first shot, but I am still having problems idling (once again pointing to vacuum problems.) After I let it idle for a minute I took off for a trip around the block. I got heavy in the throttle and I didn't notice the knock from yesterday. I guess it will be a work in progress...

John Jacobs
75 Wagoneer
Royal Oak, Michigan