cast iron Prestolite/Pertronix ignitor conversion

[jazak5]

well, after reading the articles in this site, I finally got it right I call Pertronix because their Email doesn't seem to work and voiced that with my phone call, HOWEVER the sales person was nice to deal with !!! This kit does not have a magnetic stator but uses the factory points cam to trigger the module .

well no one seemed to post pics so here they are

 

[halifaxhops]

They work really well have done a bunch of them.

 

[toolmanmike]

Yes, something new they came out with. I looked one up for a Poly distributor the other day and saw 2 different ones available. These are nice because you use the factory rotor. The one in my 318 has a Pertronix only rotor. If I remember correctly the original dual point conversion had a plastic cover for the rotor.

 

[halifaxhops]

The P-1's did as far as I know.

 

[toolmanmike]

well, after reading the articles in this site, I finally got it right I call Pertronix because their Email doesn't seem to work and voiced that with my phone call, HOWEVER the sales person was nice to deal with !!! This kit does not have a magnetic stator but uses the factory points cam to trigger the module .

well no one seemed to post pics so here they are

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And don't throw your old parts away. Slip them in a envelope and send them off to halifaxhops so he can use them. LOL

 

[694spd]

This looks like it is the answer to the problems that I had 1-1/2 years ago.
I tried to install a Pertronix kit in my 69 340 Prestolite dual point, but two different part numbers that I tried did not fit the distributor.
Pertronic Ignitor in a Prestolite Dual Point?

 

[KitCarlson]

I am curious about how well it works for accurate timing of each cylinder. Early Pertronix used small magnets in the plastic cam cover. The trigger module is a Hall effect device. The new design uses the cam peaks to trigger using a magnet biased Hall device. The early Pertronix suffered from individual cylinder timing errors relating to less than perfect magnet matching. The new Pertronix get around that issue, but the cam as a trigger target is not optimal for a couple reasons. Good Hall targets have sharp edges, so triggering point is well defined. A cam designd for points is a ramp, the trigger point varies with runout. Good targets are also annealed low carbon steel, for more uniform magnetic properties. The cam hardened for point application, making it less desirable target.

It is fairly easy to evaluate inter cylinder timing accuracy. A lathe, mill or distributor machine is used to rotate distributor. The ignition coil is replaced by resistor. Two resistors are used to attenuate the resistor peak voltage from 12V (power supply) to 5V. A logic analyser is used to capture the signal and evaluate the timings. I use a Saleae logic USB device purchased years ago. The signal goes high when triigger and is low when coil would be charging. The logic analyser software is easy to use for timing measurements. An 8 cylinder engine fires 8 times in 2 revolutions (720 degrees). The rising edge spacing should be 90 degrees apart. Simple math directly translates time variation to timing degree variations.

I don't have a new one to test.

 

[toolmanmike]

I am curious about how well it works for accurate timing of each cylinder. Early Pertronix used small magnets in the plastic cam cover. The trigger module is a Hall effect device. The new design uses the cam peaks to trigger using a magnet biased Hall device. The early Pertronix suffered from individual cylinder timing errors relating to less than perfect magnet matching. The new Pertronix get around that issue, but the cam as a trigger target is not optimal for a couple reasons. Good Hall targets have sharp edges, so triggering point is well defined. A cam designd for points is a ramp, the trigger point varies with runout. Good targets are also annealed low carbon steel, for more uniform magnetic properties. The cam hardened for point application, making it less desirable target.

It is fairly easy to evaluate inter cylinder timing accuracy. A lathe, mill or distributor machine is used to rotate distributor. The ignition coil is replaced by resistor. Two resistors are used to attenuate the resistor peak voltage from 12V (power supply) to 5V. A logic analyser is used to capture the signal and evaluate the timings. I use a Saleae logic USB device purchased years ago. The signal goes high when triigger and is low when coil would be charging. The logic analyser software is easy to use for timing measurements. An 8 cylinder engine fires 8 times in 2 revolutions (720 degrees). The rising edge spacing should be 90 degrees apart. Simple math directly translates time variation to timing degree variations.

I don't have a new one to test.

I wonder if @halifaxhops has spun some up on his distributor machine?

 

[flingdingo]

And don't throw your old parts away. Slip them in a envelope and send them off to halifaxhops so he can use them. LOL

Or put the envelope in the glovebox in case the Pertronix fails out on the road somewhere.

 

[KitCarlson]

I wonder if @halifaxhops has spun some up on his distributor machine?

My inexperience with distributor machines makes me wonder if, how and what precision they measure timing among cylinders.

 

[toolmanmike]

My inexperience with distributor machines makes me wonder if, how and what precision they measure timing among cylinders.

I would think pretty accurate.

 

[KitCarlson]

I would think pretty accurate.

Beauty is often unprecise, a bit asymmetric.

 

[toolmanmike]

Beauty is often unprecise, a bit asymetric.

The only thing on the block. There is no other technology to test that accuracy except for the Sun machines, that I have ever seen, except for a scope. Sun made those as well. Do you know of any other way to see the fluctuation that may be more accurate?

 

[KitCarlson]

I wrote about a method I use in post 7. It involves measuring time between ignition events, as counts of a crystal controlled clock. With RPM stable for measurement, same counts, means same timing between cylinders.

An example at 2400 engine RPM. Ignition events would be 6.25 ms apart. With a clock 2 mHz, there would be 12,500 counts between ignition events. 12,500 divided by 90 would be about 138 counts per degree, or about 0.007 degree per count. Looking at record of counts might be: 12,400 12,500, 12,450, 12,600.....

In reaĺity a tenth of degree quite acceptable. Timing variations below 1 degree is hard to determine by seat of pants methods, more than 2 degrees is noticable.

 

[halifaxhops]

That's pretty cool. The sun machine I can see about half a degree on average. Most of the points distribs are +-2 in the specs. I have to play around with a newer P unit and really see how accurate it is. The cam lobes definitely wear unevenly and they have to be perfectly centered on the dis shaft. I have thrown out quite a few that I would deem unacceptable.

 

[KitCarlson]

That's pretty cool. The sun machine I can see about half a degree on average. Most of the points distribs are +-2 in the specs. I have to play around with a newer P unit and really see how accurate it is. The cam lobes definitely wear unevenly and they have to be perfectly centered on the dis shaft. I have thrown out quite a few that I would deem unacceptable.

If you have interest in add-on for your machine, I can program an inexpensive $5 arduino nano board to grab trigger events and report cylinder timing deviations in degrees. To align with particular cylinders, it will need a reference signal, that happens once per revolution. It will have selection for # of cylinders, 4,6,8 and interface via USB to PC.

 

[halifaxhops]

So I can hook it up to a laptop and monitor? Prob be a good thing. Have any sort of instructions? My electronics is getting rusty really have not used it in 15 years. Ex Avionics guy.

 

[KitCarlson]

Yes, it will interface with PC or Android device with USB capable of serial communications. Some devices only implement the port for charging.
I use free TeraTerm as terminal emulator

Use will be simple. It will default to 8 cyl, it wil capture 8 consecutive ignition event times, sum the times measure RPM, display that, display deviations in degrees. It will repeat, updates every 1/2 second, faster than that changing numbers may blur.

 

[halifaxhops]

8 and six Is pretty much all I do . I am interested shoot me a pm. Does it need software or just a plug and play?

 

[Mattax]

Kit, Sounds like that will pickup independent of the Sun machine ?
They way I understand it, the Sun takes every 4th or 6th or 8th signal depending on what you select.

 

[KitCarlson]

Kit, Sounds like that will pickup independent of the Sun machine ?
They way I understand it, the Sun takes every 4th or 6th or 8th signal depending on what you select.
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The best approach is to use an independent pickup circuit as suggested in post 7. The coil is replaced by a power resistor of a few to several Ohms, Pertronix wired in normal fashion. Black wire that goes to power resistor is trigger point, attenuate with 3 to 1 resistive divider with 5V clamp circuit. I can help with that stuff. Conditioning a coil primary signal is possible, but much more invloved to shave the ~400V peak and oscillations that follow.

Not sure I follow about taking selected, 4th, 6th, or 8th. If that is what is available, it won't work, need all triggers. Not sure how the Sun does individual cylinder timing checks.

Does anyone know if the Sun has a reference pulse per revolution?

 

[Mattax]

There best approach is to use an independent pickup circuit as suggested in post 7. The coil is replaced by a power resistor of a few to several Ohms, Pertronix wired in normal fashion. Black wire that goes to power resistor is trigger point, attenuate with 3 to 1 resistive divider with 5V clamp circuit. I can help with that stuff. Conditioning a coil primary signal is possible, but much more invloved to shave the ~400V peak and oscillations that follow.

Not sure I follow about taking selected, 4th, 6th, or 8th. If that is what is available, it won't work, need all triggers. Not sure how the Sun does individual cylinder timing checks.

Does anyone know if the Sun has a reference pulse per revolution?

The Sun uses an amplifier (see it on the left side of photo) for magnetic pickup distributors. I'm not sure where the signal then goes. But it seems it must pickup every pulse whether points or amplified. On the lower right of the machine there is a selector switch for the number of cylinders. However that might just be for the tach. I do know the tach signal relates to a points type unit working off the machine's drive, not from the distributor. That's about the extent of my knowledge on the workings. Halifaxhops knows a lot more about them than I.

 

[halifaxhops]

It is set by the amount of signals from the distrib from what I can tell 4, 6 or 8 for the tack and dwell. I think the machine itself sends out a constant + and it is interrupted by the points/pickup to trigger the light coil. No mater where the switch is set the light come on by the lobe for lack of a better term.

 

[Mattax]

That makes sense. Explains all the red arrows you can see captured in the photo.

 

[halifaxhops]

Nice machine from Paramount? I know the amp is Marks.