The following describes how to upgrade the Ford DuraSpark ignition in 258ci (4.2L) I-6 CJ's and YJ's to Ford's TFI (high energy) ignition. All 1978 to 1990 models used the same Motorcraft distributor and ignition and so are eligible for this upgrade. If you have a 1977 or older 258ci (which used a Delco distributor w/breaker points), you can still do this upgrade, but you have to find a Motorcraft distributor and ignition module from a 1978-1990 model.

The Motorcraft Duraspark ignition is one of the most dependable ever released from the factory. The distributor itself is a very good unit, and can easily be tuned and used for extreme performance upgrades. The limitations of this setup include the small 'well' type distributor cap, the short rotor, the low energy spark plug wires, and the low output ignition coil, which are all antiquated:

• The distributor cap design is left over from the 1920's. (WWI technology)
• The plug wires haven't changed in any distinct way since the 40's. (WWII technology)
• The ignition coil is still based on the oil-filled units that appeared in the 1920's. (WWI)

This upgrade will bring your Jeep ignition system into the mainstream 80's technology. It uses as many stock, off-the-shelf parts as possible so they can be replaced at any parts store, which keeps costs down and insures availability of replacement parts. Try to stay with factory groupings - if all the parts are from the same year, it makes it easier to remember where things came from.

The Ford Thick Film Integrated (TFI) coil is Motorcraft's answer to the GM HEI coil, and out-performs GM's HEI by 1-1/2 times, The TFI coil works with all Duraspark ignition modules and can be mounted in any orientation. The newer model distributor cap and rotor have the posts spaced further apart, which eliminates cross fire (especially with the higher powered spark the TFI produces). High quality 8.8mm plug wires round out this configuration to ensure the spark makes it to the plugs.

Stock Parts To Replace:

• Distributor Cap
• Rotor
• Plug Wires
• Distributor Advance Springs
• Ignition Coil

Replacement Parts:

FROM: 1982 Ford F-150 pickup with 300ci I-6 Engine.

• Distributor Cap Base
• Distributor Cap
• Rotor
• Aftermarket 8.8mm Spark Plug Wires

• TFI Ignition Coil

• Distributor Centrifugal Advance Springs - Mr. Gasket P/N 925D

Installation:

Just remove the old parts and bolt on the new, regap the plugs to .045", and reset the timing to 8-10 degrees BTDC.

The only tricky parts are:

• You have to cut off the connector going to the stock coil and splice a wire to the new TFI coil.
  
• The TFI coil is odd-shaped and so difficult to mount. I got around this problem using four 10x3" bolts and four 2-1/2" pieces of rigid tubing: I bolted it to the inside fenderwell by the distributor, using the tubing as stand-offs.

Send comments or questions to Joe Church (jchurch@lex-con.com)