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Jacobs Ignition to fix the Mopar MPI ping?

897 Views 6 Replies 2 Participants Last post by  Sycho15
Has anybody had any success swapping in a Jacobs Omni Magnum ignition system to reslove the pinging and cold start issues associated with the Mopar MPI upgrade? I'm looking for something to increase the top end until I get the 4.0 head replacement. Any comments, positive or negative would be appreciated?

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With what you'd pay for the Jacobs, you could get a nice 'used' 4.0 head, even have some of the machine work done (valve job, deck, etc), buy a good quality head gasket, AND rent a torque wrench. If you're thrifty or have a buddy who does the machining cheap, you could probably even swing a HEI upgrade too. Either way, don't spend money on the Jacobs to try to fix a problem elsewhere, you'll only be dissappointed. Suck it up and dive into the 4.0 head. The increase in performance and mileage will be very rewarding. Then, if you still want the Jacobs, go for it. Might not have been the answer you wanted, but I hope it helped. Happy Jeepin'!

I have the complete mileage master system in my 454 blazer. Put it in with a totally gone thru motor, so can't comment on any improvements, only to say that almost 4 years later still going strong.
The one thing I hate about Jacobs is there attitude/customer service. I once had a coil grounding wire from a omni pak burn up on me, and they made me pay for the new one. Every time I've talked to them on the phone they've had the attitude like "spend some money or get off the line". For the price I expect a little support, y'know?
One more thing though-I think their spark plug wires are hands down the best by a long shot.

89 XJ, 83 CJ-7, 79 Blazer, 67 CJ-5
I'd suggest dropping by your local Jeep dealer and having the timing retarded. The techs have a tool called a DRB 2 that can be used to retard the timing in 2 degree increments up to -6 degrees. This usually solves pinging problems and they shouldn't charge too much (1/2 hr labor would be reasonable). Hope this helps.

Sounds like you need a chevy HEI swap.
I think cj-8/5.2mag made a very good point. I would try that first.
It has to be a timeing thing. After you get that fixed
the HEI would have to help performents at a lower cost.

One more suggestion, running a 180 degree thermostat may help also, if you installed the 195 one from the kit. A 160 would be too cold.

If you run a GM HEI ignition you can get an adjustable vacume advance from Crane Cams- it should be available at any speed shop. This has two things to help you adjust vacume. #1 you can put an allen wrench (supplied!)into the vacume hole and adjust it in 2 degree increments with two full turns of the wrench or #2 there is a little black oval with notches that goes on the rear bolt and you adjust it to hold the vacume arm further away or close to adjust vacume in 2 degree increments. I have JUST bought and rebuilt a HEI distributor to swap into my Jeep and all I need now is the AMC V-8 Distributor Drive gear...and some help from friends on getting everything adjusted and bypassing the stepper motor so I can rip out the computer and go under water up to the top of my windshield and snorkel!

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