Bosch Dizzy - Points or Electronic

[67rebuild]

My question is three fold ....
1, should I nuke the points and install the electronic ignition? Pertronixs seems to be the choice? 2, My distributor is # 0231169008 seems as if they don't make one for that number .. so what is the difference between it and the 009? I can't seem to find any help from Bosch
3, dose anyone know which engine that distributor originally came on?

Thanks
Eric

[304065]

Eric,

Are you rebuilding a 1967 normal? Most guys here post their car in their signature line as a guide.

A Bosch 0 231 169 008 is for a '73 2,4T. See here: Bosche Distributor 0231169008

Right away, you can tell that distributor won't fit in the 2,0-2,2 case, because the distributor bore was enlarged in 1972.

I am not a big fan of the electronic ignition because it's not necessary, if you are using a CDI or other modern ignition, and diagnosis is more complicated because you can't see what's wrong, you need an oscilloscope to measure.

See here for everything I know about SWB ignition.

Before there was BHKZ: SWB engine electrics

[67rebuild]

John,

Thanks for the info and the links its very helpful ... I found this car in garage covered in junk. It's solid and came with a few boxes of new 20 year old parts. Its a bit of a mystery car with 911 parts from 67 to 74. After 1 year and mega hours of research and fun it runs and soon will getting ready for paint (just sorting out a clutch issue). For now I'll keep the points, it seems to rev well and when it comes on the CAM it really begins to make power.

Thanks again ...

[john walker's workshop]

points, can be adjusted, cleaned, filed, jerry-rigged when you stall out in the middle of the desert. with a dead pertronix, you're buzzard bait.

[jluetjen]

Looking at John Walker's comments a different way,

- With your points you're always going to be adjusting, cleaning, filing and jerry-rigging.

- With electronic (Crane optical in my case), you set it once and forgetaboutit!

[304065]

John,

Has the Crane optical trigger worked well for you? There was one in my '66 when I bought it and I hated it, because I could never tell if it was working.

Now, I agree that if you had a '64-'68 911 that was still running the old Kettering ignition (battery-coil-condenser) the current flowing through the points is high enough to pit the contacts, requiring filing and adjustment about every 10,000 miles (which is an eternity for most SWB 911's!)

However, the current flowing through the points trigger circuit for a Bosch CDI is only 420mA. There's a 33 ohm pullup resistor inside the CDI . . . E=IR . . 14=.424*33. . . so 420 mA total flows through the points when they are closed. This is so small that Porsche eliminated the condenser across the points in 1969. About FOUR amps is the practical limit for points which nobody ever sees.

Nor is the CDI system particularly sensitive to Dwell, for that matter. With Kettering-ignition, you need time for the magnetic field to build up in the coil before the points open. The dwell period for a 911 is around 38 degrees of distributor rotation. That means that when the crank is turning 7000 rpm, the points are closed for 1.8ms. The capacitor in any CDI charges in the nanoseconds range, so you don't get any of the resultant issues of reduced coil charge at high RPM.

You do, of course, still experience point bounce when the resonant frequency in the spring of the points equals the rpm of the distributor divided by six. This is, of course, the reason for dual-point distributors: to ensure that ONE is triggering when the other is off somewhere synchronously vibrating. I have never found this to be a source of misfires, however, through about 7300 RPM. It might occur higher, though.

[911pcars]

Just to add to the discussion.

The rubbing block gradually wears as it follows the contour of the distributor shaft cam, moreso without cam lube, and as it does so, the dwell increases (gap decreases). For every degree of dwell change, so does the ignition timing. Thus, over time, the ignition timing will retard. Be aware of this maintenance and tune up issue when using breaker points.

Sherwood

[fastfredracing]

I had one of those crane units fail. I like to run points, and msd 6al if a good cdi box is not available.

[911pcars]

Just to bring the survey numbers up to 3 or 4, my Crane breakerless has been good for the past 9 years. Knock on wood. I still carry the points and condenser in the on-board spare parts box just in case the car runs out of spark at Horror Hotel.

Sherwood

[67rebuild]

Here is a some-what unrelated question but it is a distributor question.... when I got the car the vacuum advance hose was not there, I can't even find a spot where is might have plugged into. Is this an issue? The engine (originally CIS) has been converted to Carbs, do I need the advance?

[mikespitzer]

Related to this discussion --
I also have a 1973.5 T with the 0231169008 distributor
This of course uses the "Backwards points" as some people call it.
Question --- does anybody have a link and/or part number for the correct "reversed" points used in this distributor ?
I have ordered 4 sets now that were supposed to be correct --- but I keep receiving "standard" points

Thanks

[E Sully]

These are correct for my 0231169008, 90160296004
I had the same problem getting the correct points years back.
https://www.pelicanparts.com/More_Info/90160296004.htm?pn=901-602-960-04-OEM&SVSVSI=5878&DID=17927
In the photo you can see how they reversed the points in later years, my '73 is on the left, and '77 on the right.

Points for '77 distributor.
https://www.pelicanparts.com/More_Info/91160293600.htm?pn=911-602-936-00-OEM&SVSVSI=787&DID=17927

[faapgar]

The points with CDI have always been simple and dead reliable.Just use the proper grease on the rubbing block with a little on both sides.Set the dwell to 38 degrees so as it wears it will get to 40.The points really never go bad.The only issue I had in 50 years is a slight oil film on the contacts which can make your tach bounce a bit or create a non start.My cure has been to always carry a book of matches to place between the contact points to wipe them clean.I have always carried a spare CDI for road trips and have never been stranded.Fred