CDI Replacement Questions

Craig Stevens · 01-01-2002, 10:35 AM

On My 80SC The Tach Connection in the CDI box works intermittently. I am thinking of replacing it. What is the difference between the permatune unit & The MSD unit ? What would you guys recommend? anyone have experience with either unit? I believe from some of the threads that I have read that with the MSD unit you have to rewire,change the coil & regap the plugs. I don't know anything about the permatune unit,but pix that I have seen look like it is a direct plug in replacement. Should you use the blue coil with the permatune, & do you have to regap the plugs? finally, is there any performance enhancement of one over the other? I just had my wrench do a complete engine rebuild. what a huge power difference. I am anxious to put some miles on the rebuild before I rev it past 4000RPM.
Thanks in advance for any help. Craig

Early_S_Man · 01-01-2002, 11:18 AM

Craig,

If your tach works intermittently, then corrosion somewhere along the path from CDI-unit to tach TD lead is what I would suspect ... not a failing CDI-unit!

The Perma-Tune unit IS a direct, plug-in replacement for the Bosch CDI-unit! The MSD boxes require changing the coil, and add-on optional boxes to mate to Porsche electrics ... and lots of word-of-mouth help to get it working properly! Very little, if any, Porsche-specific info is available from MSD ... everything seems to be generic, or GM-oriented (Chevy, if you know what I mean) and you will be treated as an 'oddball' when asking for Porsche info!

I suggest getting a set of the 'Electrifix' brushes, and starting at the 6-pin connector at the CDI-unit ... clean EVERY male and female connector, and 'retension' the 1/4" female Faston connectors with needle-nose pliers, and test with a male 1/4" connector crimped to a 4" piece of 10-12 ga wire to check for drag when pushing on the female plug. The 'gap' in the ears of the female Faston ahould be less than the thickness of the 1/4" tab, but not closed-up entirely!

The forward 14-pin connector at the fuse/relay/CDI panel mates to the main body wiring harness, and the TD lead is present there. Oxidation is sometimes a problem with the silver-plated pins and sockets, but special care must be taken not to damage the silver plating! Soft bristle brushes and isopropyl alcohol is the cleaner of choice, though some of the liquid cleaning/dipping solutions for silver flatware might work, too ... followed by thorough cleaning with isopropyl alcohol. Silicone grease applied lightly to the connectors, which the military has been using for over 50 years to vehicle electrical systems, seems like a good idea for protection against oxidation and corrosion.

Craig Stevens · 01-01-2002, 11:46 AM

Warren, Thank You for the information. I will follow your suggestions & let you know how I make out. Craig