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Rumble-Bee Rumble-Bee is offline
Air Cooled-6
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Join Date: Apr 2009
Location: Ventura, CA
Posts: 41
I went through this on my 78 3.0SC engine in my 74 Targa (a terrific combo). The green wire was baked over the years & was causing the car to intermittently quit when the coax shorted. I found out by moving it while the engine ran -- and it stalled and wouldn't restart until I could attain a good position (this got worse every time I moved the wire). I didn't want to buy the (expensive -- and short) green wire (with the connector) going to the CD box. I wanted a single wire to go from the dizzy straight to the CD without a connector in between. So I made my own coax wire because I couldn't find anything I could use off the shelf -- they all had a thin gauge core & a massive amount of shielding -- and the OEM wire appeared to have matching impedance for both. I used a standard 16 gauge wire for both the core and the shield. I matched the length of the core wire, then stripped the insulation from the shield wire and used the bare wire bundle to meticulously spiral-wrap it around the core. It was hard to spiral an equal length wire around the core --I had to untwist the strands & then spiral the flat collection of strands around the core so that I could completely shield it with the exact same length & impedance. Then I used heat shrink tubing to encase the new coax. I soldered the old dizzy connectors to the new coax so it would plug on like the old stator. On the CD end, I soldered a pair of spade connectors that perfectly fit the CD connector into the When I started it -- it backfired through intake so much (Thank you, pop-off!!!) that it barely ran -- timing was very retarded, so I twisted the dizzy but found I could not advance it enough. Then I pulled the dizzy and advanced the gear by 1 tooth -- now I had the opposite problem. The timing was extremely over advanced, the car could barley crank -- I had to twist the dizzy to full retard -- but it was still way advanced. This really got my head scratching because it seemed that timing was now a HALF tooth off on the dizzy. Once I thought it through, I realized that the polarity of the stator got reversed -- and that caused the CDI to read a shift in the pulse of about 30 deg. Those teeth on the star wheel (reluctor) create a small voltage pulse when they pass the stator (pick-up coil) -- and the width of the star elements were just about the right amount of degrees in error. So now the CD was either seeing the pulse as the tooth was passing the pick-up as BEFORE instead of AFTER (or vice-versa)-- causing a timing change of about 30 deg. Once I switched the coax connections to the CD box -- it fired right up and has run great for 2 years now. Someone mentioned using a 928 coax -- never thought of that -- may be a really good idea --it does look a lot longer than the 5" wire of the 911 part, but appears to still use the same connectors (although its even more expensive). I made my own because I feel that midway connector is just not needed and adds another failure pointe point.

Last edited by Rumble-Bee; 11-26-2016 at 11:07 AM.. Reason: Fact corrections
Old 11-26-2016, 10:21 AM
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