1978 308 GTS twin dizzys running single pertonix set up in the rear dizzy. When I advance my dizzy fully, I am short of the designated timing at 5k. I want to move it one dizzy spline tooth advanced. So I think I should rotate the rotor one dizzy spline clockwise and re-insert, then fully retard the timing and thus be pretty close to where I was when I started. I don't think the timing adjustment on the dizzy is one full spline from what I read. Agree? Also, my front/rear timing is off by 3 degrees at 5k RPM. I believe this is due to the slack in the double pertronix mounting plate or general tolerance pertronix is willing to live with. Where would you set the timing? Spot on one bank? Over/Under? spit between the banks 1.5 over and 1.5 under? Cheers Ken
Id fix it and make it right. To me 3 degrees wrong is wrong. To start with did you index the firing point/rotor/cap position?
The three degrees is the difference between the two pertronix ignitors as mounted by pertronix at the factory. In other words they are not exactly in sync on the mounting plate. That is a manufacturing tolerance pertronix accepts. Unless I want to modify the pertronix unit to somehow move one of the ignitors with respect to the other one, I am stuck with 3 degrees difference. I am ok with three degrees difference. My question is where to set timing advance at 5k? 38/35, 35/32 or 36.5/33.5? Also, I figured out the question on advancing the spline. Rotating the shaft clockwise one spline, then fully retarding the distributor gets to almost the same place as it was one spline back and fully advanced.
I would split the difference. Having one bank retarded 1.5 degrees and one bank advanced 1.5 degrees in a negligible difference. You would be hard pressed to get most Ferrari's with twin distributors within that specification at 5000RPM.
3 degrees difference between the two banks is too much. You might also find out that such a Pertronix setup can have up to four degrees difference between cylinders due to the sleeve design. My fix was to create my own setup, have a look: http://www.ferrarichat.com/forum/308-328/453748-bosch-ignition-s159-double-distributor-setups.html
As I mentioned in the other thread I did mount my own second sensor making it adjustable with respect to the first and then the entire plate rotates as well. I used a very large brass? washer from Mcmaster as the rotating base for the second sensor. Honestly it wasn't that hard but you do need to have access to a distributor machine to align it.
You can also elongate the module mounting holes on one module and slide it to either side to take up the difference.
Thanks for the feedback. Did you do that? Got any pics? which way is which + or -? Can you adjust in car or do you have to take the distributor apart to adjust?
If you want to make this accurate and since we're talking about 3 degrees here I assume that you do the best thing is to remove the distributor and align it on a distributor machine. The large rotating washer just makes the adjustment much easier. Elongated holes CAN work but it requires more fiddling. Once you have it spot on use some penetrating loctite on the sensor's securing nuts.
Which way depends on whether you want to advance or retard the ignition. This is a PerTronix approved method. You will have to remove the distributor to do the job. Be careful with Loctite. The module earths through its own chassis and Loctite can insulate the module which will take the earth away and stop it working.
