Points and distributor

[ennisk1]

Still contemplating the changes I want to make to the ignition sytem on my 71 911E. It has a Perma Tune CD box, stock coil, and the Bosch distributor. I just changed to a hotter plug. The car still is still set up with points.

My question is, any recommendations on swapping out the points to an electronic set up? Performance carries the Crane set up, but I'm curious as to what else is out there. Also, what about the coil? Any recommendations or just stick with stock? Thanks.

[Eric911S]

Hello; I use the Pertronix units. You can buy them from Paragon Products. You never have to adjust points again and no point bounce at high RPM. Thanks Eric

[304065]

There is no compelling reason to change from the Bosch points. I don't know what resistance value the pullup resistor inside the Permatune carries, but the one in the Bosch is only 33 ohms or so, which results in only 420mA of current being carried in the points circuit. That's enough to trigger the firing of the ignition box and the tach, but not enough to erode the points appreciably in tens of thousands of miles.

The other problem with the Pertronix is when it fails you can't tell.

My advice: Porsche designed a good system, stick with it. I've used it in 16 club races well past 7,000 RPM. Put in new Bosch points, set the gap and the dwell and drive.

Why the "hot" plugs? If your MFI is running rich (most are) you should deal with that directly vs. using a plug that's hotter for self-cleaning but that will increase the likelihood of preignition.

[sithot]

Ditto.

The Pertronix is a nice setup, but like John said, it if goes bad you are stuck. They do hold up pretty well from my experience. I'm on the fence here although I have had good experiences with the Pertronix setup.

Anybody have a line on where one can pick up a Bosch coil that is compatible with a CD? I have a Delta which will use the stock coil but am leaning toward an original 3 pin CDI even with the inherrent issues that will likely pop up with the tachometer. (67 car).

Best,

Tom

[304065]

Tom,

The Delta Mark X is a cool period piece, I would save it for shows.

You can use a cheapo Bosch Blue coil with the Bosch 3-pin CDI, someone has tested this for a couple hundred hours and reported no failures.

If, however, you want the greatest power from the 3-pin, the correct coil to use is the original Bosch. Dr. Steve Weiner has tested that on a Dynamometer, no less, and found that the electrical engineers at Bosch were not drinking at lunch the day they sized the coil! (Either that or they designed it in the morning!)

The "line" on that is the classifieds here and elsewhere. Do NOT get the silver coil, it's a paperweight.

Or if you want to hide an MSD or an M&K somewhere in the car and run its 460V output through some shielded wire back to the stock coil location, that would work well and give you a fat spark at a price lower than Bosch, insofar as the Bosch isn't original either.

But what to do about the tach. I have written much both here and on Pelican, links below. The short answer is that your '67 and my '66 have tachs that require a low-impedance high voltage output, and they will NOT trigger properly off the 11 or 12 volt square wave output from an MSD, Bosch or M&K. So the inelegant fix is to use a tach adaptor, which is basically a big induction coil with 12 volts bled into it, which will create a huge voltage spike on the black/violet tacho input wire. Think of it as running a second coil in parallel with the first, although electrically that's not what is happening.

A more elegant "period" fix is to locate a Bosch "intermediate unit" can such as that described in the second thread below. These are hard to find.

The ultimate fix, of course, is to replace your VDO tachometer internals with a modern VDO movement. Would you believe that the screw spacing to mount the face to the movement HAS NOT CHANGED from 1965 until today? So if you can get the chrome ring off without making it look like Fido chewed it, you can replace the old low-impedance one-shot movement with a modern high-impedance movement and none would be the wiser.

Below is basically everything else I have learned about SWB electrical systems and tachometers. Be sure to add your knowlege.

http://forums.pelicanparts.com/showt...hreadid=252299

http://forums.pelicanparts.com/showt...t=ballast+unit

[69Sman]

You can use a cheapo Bosch Blue coil with the Bosch 3-pin CDI, someone has tested this for a couple hundred hours and reported no failures.

If, however, you want the greatest power from the 3-pin, the correct coil to use is the original Bosch. Dr. Steve Weiner has tested that on a Dynamometer, no less, and found that the electrical engineers at Bosch were not drinking at lunch the day they sized the coil! (Either that or they designed it in the morning!)

The "line" on that is the classifieds here and elsewhere. Do NOT get the silver coil, it's a paperweight.

AGREED! Especially the part aboutl the Silver Coils. THEY SUCK!!!!!!!!!!!

Tom, I recently located 3 original Bosch Black Coils, and bought them all. They pop-up now and again. That's definitely the way to go. (Sorry, need all 3.....(

[sithot]

Thanks, John.

Loren at Systems Consulting did a look-see on the Delta and found it in good order with a few loose items that he fixed. This is the unit with the on/off switch that allows you to go from CDI to regular point/coil trigger.

Loren's thoughts on the Delta were that it was a very good unit that did not give a lot of trouble. The car is set up for it and I might have another go with it since I can prove it did get installed in the car in 1968. That was a funny piece of documentation. Somebody sent me a Pano add from the era with the unit advertised for $39.95.

I'll read up on your posts and make an informed decision.

Again, thank you very much.

Tom

PS: I have a NIB 6 Volt Delta unit too. I thought it was a 12V when found scrounging in the parts bins at a shop. Shucks.

[Eric911S]

Hello: You can use the black Pertronix coil as well it works great with the factory CD box. I have never had a Pertronix unit go bad so far in 16 years or so. The only bad ones I've replaced are from owners connecting them up wrong. Those that like the points and the adjustment that they take when the rub strip wears down then go for it. For those that still run coils, condensors and points you don't need the CD box it is highly overated ;-). Thanks Eric

[304065]

Eric, LOL, there are only about four guys still running "kettering" ignition! Although I drove an original '65 this summer and it ran great up to 6K (the owner was in the car and I didn't feel it RIGHT to go above 6k )

The real reason Porsche went to a CDI system is that six cylinders at 38 degrees of dwell is a 63% duty cycle. At 7000 rpm, or 21khz, there was barely time for the coil to make the round trip from charged to discharged. With the capacitor charging and then discharging into the coil (really, now a transformer from 460v up to 30Kv) there was a whole lot more time in the process.