To Pertronix or not ?

[dicklague]

I have had Pertronix in my 1973 2.7 for about 15 years. I will check my servicelog and give the exact time and mileage.

NO problems. I carry a spare set of points and even another Pertronix, but have never needed them. I am talking 100,000 miles of service.

Best $100 I have spent on this car!!

I later installed a good CDI and transformer coil [NOT MSD] and that has made a HUGE difference in my MFI equipped engine.

Install it and forget it....it just works.

[mysocal911]

Originally Posted by Jim Dunham

Does anyone know if using the stock CD coil is OK with the Pertronix? the instructions say "minimum of 1.5 ohms for the coil" and the stock Porsche coil measures 0.7-0.8 ohms.

That only applies if the Pertronix is directly driving the ignition coil. When used with the original Bosch CDI,
the Pertronix is just a points replacement. Given that, it's questionable if the Pertronix has any real benefit over
the original distributor points.

[mysocal911]

Originally Posted by Lorenfb

"The cam in the distributor provides the triggering through the Hall effect system in the Pertronix."

Which has the reliability problem of the Hall Effect semiconductor being in a high
temperature environment. With the Bosch CDI system, the ignition points only
switch a very low current and the points basically last forever. So there's no
real benefit to using the Pertronix and a downside because of the reliability
issue, i.e. another ignition element that can fail.

That sums it up!

[dicklague]

Originally Posted by mysocal911

That sums it up!

The rubbing block experiences no wear ......forever? I doubt it.....well I know it is not true.

Is it again forum rules to quote yourself??? ;-)

[dicklague]

I looked it up and the Pertronix was installed 12 years ago and 102,000 miles ago. Has not been touched, and no problems since then.

I guess it is surviving its hot environment that the naysayers claim it will not.

This thread is so old that some posters are using the former names and current log in names, and even quoting themselves!!

Bottom line is the purists are going to tell you that points are terrific and the way Porsche intended. I kind of feel if Porsche had access to Hall effect ignitions when the early cars were built they would have put them in......well in reality they did put them in later models as soon as they were developed and reliable.

If points are just fine for us, and don't question the wisdom, why did Porsche put in a modern system when they were available?

Same goes for the old CDI. Some posters on this thread argue that they are fine and adequate and preferred and even that you will not see any improvement. This has not been my experience. When I switched to a modern CDI [not a red MSD ] it was a huge improvement. Much better starting, better running, better idle, and I get the benefit of a soft PROGRAMABLE rev limiter [no harsh rotor limiter] and data gathering for MAP, RPM, etc..

There are even CDI models now available that look like the old Bosch CDI from Parts Klassic, and others that have modern electronics in a look alike box. These units sell quite well.

Bottom line, make up your own mind. We have seen here guesses that Pertronix will not be reliable, and anecdotal evidence from users including me that they are reliable.

We have also seen claims that points don't lose dwell and never wear out, and our common sense and experience is that they do both.

[mysocal911]

Originally Posted by dicklague

The rubbing block experiences no wear ......forever?

So it wears a little over 100K miles and the timing might get retarded a little, maybe one degree for all cylinders,
versus random timing per cylinders with the Pertronix.

[Jim Dunham]

Well - I installed the Pertronix on the 2.7L distributor in my stock 3.2L w/ 46 PMO carbs and it's no better. Just so hard to start; takes many cranks and many throttle-throttle-sputter-throttle-die-try again - throttle sputter. Was hoping I had an ignition issue (since 90% of carb issues are ignition or mechanical).

Once lit, it does'nt run all that great until warm and RH carb needs the idle mixture screws almost falling out to run best. LH carb is just right - about 2 turns out.
Did full COLD leak down and it looks normal for an ORIGINAL used 3.2l engine

#1 = 5%
#2 = 16%
#3 = 8%
#4 = 13%
#5 = 12%
#6 = 5%

No audible noises or leakage heard during the testing.
RH carb pops - like it's lean. Yes, I've pulled the carbs apart and cleaned/gone thru them with no luck. did'nt find any smoking guns. All three idle mixture screws need full out to run best so it's not one cylinder. All throttles flowing equal air.

46mm PMO Carb specs:
Idle jets = 55
mains = 150
airs = 200
emulsion = F11
WR7DP spark plugs
3 pin Porsche CD box
CD coil

Thinking I may try another set of carbs I have up on the shelf - 40 PMO's and see what shakes.
I am so thru with carbs. It's time for FI but it seems no one makes a complete turn key system.

[69911e]

Jim: Did you try a different CDI? I recently helped a friend fix his 914-6. Very poor starting, bad running poor idle, lots of popping out carbs. Turned out to be the CDI box (components are getting a bit old). There is a specialist that repairs and can test yours, but from your signature, it seems likely that you may have another box around.

If you want FI, why not use the OEM 3.2l injection? Easy conversion as the original computer and injection harness connects with only 3 or 4 connections to your car. Very easy to do.

For those interested, I am at over 150K miles on my points with no measurable wear or adjustments so far. I do lube annually with the Bosch point lube Grady Clay or John Walker suggested many years ago.

Just for clarity, early in this tread I posted about removing the pertronix and reverting back to points. I never had a failure of the Pertronix and the car always ran, just not as good as on points or as good as Porsche designed it to. I tried to explain this with my data, science theory on the unique compact design sacrifices, and the information I received from Pertronix that they never considered or tested for a difference in cylinder timing. This is posted only for those interested in more insights.

[Jim Dunham]

That's a good idea - I have other 3 pin CD boxes I can try. Do these CD boxes "lose strength" over time? I also have a MSD unit but was trying to stick to "old school". I got the 3.2L without the intake and wiring/DME so went the route of carbs. I'd put the 3.2L intake on if I had the hardware!
Like you, I've had 911's with points and no troubles. When I went to carbs, I had to find a 2.7L distributor (rotates same as the 3.2L just have to swap distributor drive gear) and really wanted to convert the 3.2L to hall effects while I temporarily used the 2.7L. Figured the Pertronix was a quick upgrade.
After staying up all night reading about PMO carbs, the one thing I didn't do is close up the idle air bleeds to zero before starting my tune/calibration - these are lightly used PMO's I bought off the PP classifieds and unknown used history. So I'll try the CD box change and idle air bleeds today and see how it goes. Thanks for the feedback. I should start a hunt for 3.2L intake hardware and FI setup!

[69911e]

Originally Posted by Jim Dunham

Do these CD boxes "lose strength" over time?

Yes, without going into unnecessary details, there are components that loose important properties with time and heat. You need to test with a known good one.

[Paulporsche]

I used points in my 77 with 80 engine car for nearly 30 years. The point contacts lasted a long time, probably because of the triggering aspect with the CDI others have mentioned. However, the rub blocks seemed to wear so fast that I was going from 35 degree to 60 degree dwells in less than 1500 miles, which obviously affected performance, mileage, and starting. This started with a batch of new points that I stockpiled about 15 years ago.

I just installed an Ignitor 2. Easy installation. I've just gone out for my first test run with great results. Obviously there is still a lot of testing to come but so far so good.