Green distributor wire polarity

[91166 Carrera]

I'm having a problem getting my timing to come into spec with my twin plug 964 distributor. I've read a number of Pelican Forum posts but still can't find exactly what going on with the timing. Here's my story.
My car is a 1976 Euro Carrera 3.0 targa. A number of years ago I had the original points distributor removed and installed a 911SC distributor that turned counter clockwise. Later I had that distributor removed and installed a 964 twin plug distributor where the guts of the SC distributor were installed into the twin plug distributor and the drive gear replaced so that the distributor would turn clockwise. The engine turns clockwise. I'm also running the M&W Pro-Drag ignition CDI unit, which has a single plug that runs 2 independent coils. The green wire, with yellow connector, appears to be in good condition. I sent the distributor to Jerry Woods and the twin plug distributor makes 20 degrees advance but when in the engine it only makes 15 degrees advance. The engine is timed at 5BTDC and makes only 20BTDC total advance. The total advance timing should be around 30BTDC.
Three questions: 1) if the SC green wire was not corrected for polarity (because the distributor now spins clockwise) could this be the cause of my timing problems? 2) if I reverse the polarity, by using jumper cables for testing purposes, will this damage the M&W CDI unit? 3) Is there a test that can be performed, other than using an oscilloscope, to determine polarity?
Does anyone have a suggestion for the timing problem?

Carrera 91166

[mysocal911]

Originally Posted by 91166 Carrera

I'm having a problem getting my timing to come into spec with my twin plug 964 distributor. I've read a number of Pelican Forum posts but still can't find exactly what going on with the timing. Here's my story.
My car is a 1976 Euro Carrera 3.0 targa. A number of years ago I had the original points distributor removed and installed a 911SC distributor that turned counter clockwise. Later I had that distributor removed and installed a 964 twin plug distributor where the guts of the SC distributor were installed into the twin plug distributor and the drive gear replaced so that the distributor would turn clockwise. The engine turns clockwise. I'm also running the M&W Pro-Drag ignition CDI unit, which has a single plug that runs 2 independent coils. The green wire, with yellow connector, appears to be in good condition. I sent the distributor to Jerry Woods and the twin plug distributor makes 20 degrees advance but when in the engine it only makes 15 degrees advance. The engine is timed at 5BTDC and makes only 20BTDC total advance. The total advance timing should be around 30BTDC.
Three questions: 1) if the SC green wire was not corrected for polarity (because the distributor now spins clockwise) could this be the cause of my timing problems? 2) if I reverse the polarity, by using jumper cables for testing purposes, will this damage the M&W CDI unit? 3) Is there a test that can be performed, other than using an oscilloscope, to determine polarity?
Does anyone have a suggestion for the timing problem?

Carrera 91166

Call these guys; M&W Pro-Drag ignition CDI unit

[91166 Carrera]

Dave, thanks for the information. Sounds like a good place to start.
Harry

[stevie 77 930]

This was discussed on the 930 forum when dealing with early Turbos that had counter clockwise distributors

https://forums.pelicanparts.com/911-930-turbo-super-charging-forum/1038533-converting-later-green-wire-early-turbos.html