Maximize your Ignition/Points Distributor after 12 Volt Negative Ground Conversion

[Sharps40]

Been a while since I've posted.  Ol Bessy (37 Dodge) is running daily on her new SBC and TH350 for three years now.   Yep, i used all GM power and drive line for off the shelf, anywhere, parts availability and its saved my bacon on a long out of state trip on one occasion.....no waiting in a hotel for overnight delivery of an antique repair part....but, I digress.

 

So, you still want/need to run the old flat head....but for reliability/other reason, you've converted and rewired from 6v+ ground to 12v_ ground.   Good for you, if nothing else, a fine safety upgrade as you'll have much brighter headlights.  {Most especially if you've properly taken the load off the switch using relays to deliver a full 14.2v to the lamps.)

 

But, in so doing, you've likely not taken advantage of the 12v- ground capacity to upgrade your ignition and engine performance.   Options include an expensive 12v hei, or a somewhat difficult conversion of your points dizzy to slant 6 electronic.....but there's an easier and more affordable way, and it can be hidden if your a "looks" purest.

 

 

 

 

Edited June 22, 2023 by Sharps40

[Sharps40]

Some background first....

 

 I didn't know this and find it very interesting.....might well quick fix a road side break down for the bazillions of us running an HEI distributor.

 

I run a GM HEI (Chinesium copy cause at the time I was assembling, A Genuine Item wasn't in the budget.) Since then I located in the spares at Dads house a fine condition GM HEI Distributor. I won't keep the entire dizzy in the trunk when traveling but the genuine gm module can be stowed against a road side breakdown.

 

Comparing the two, I noted my Chinesium module is a 4 pin and the GM Module on hand is a 5 pin. Did a bit of quick research and it seems pin count really doesn't matter. Running a 4 pin dizzy I can swap in any 4, 5 or 7 pin module to mine and it'll work fine. Even the Buick 3 pin module can be wired to replace my Chinesium unit or used to control points dizzy should I ever go back to that.  (I did further research and found even the common 4 pin can be wired to any points dizzy for nearly infinite points life and full 12v-14.2v power {ballast resister eliminate} to the coil at all times.   Neat stuff.)

 

Essentially, the common 5 pin uses one pin for spark knock....not needed on mine. A rarer, 2 year 5 pin, uses one pin to retard timing 5 degrees, not needed on mine. Same with the seven pin, just swap it in and ignore the additional pins. The odd 3 pin can be used but requires rewiring.

 

So, nice to know I've got a spare in the trunk and if i ever needed a parts store on the road, there are many choices against their inevitable "4 pin shows in stock but ain't actually on hand" scenarios.

 

Edited June 22, 2023 by Sharps40

[Sharps40]

Here is a link to using a GM 4 pin control module to maximize your points distributor.   A motorcycle article but applicable to cars too.   Should work with any distributor and your 12v- ground system.   Don't forget to heat sink the module at your preferred mounting location. 

 

There is an option here to toggle between points controlled ignition and module controlled ignition.  e.g In the rare event a Genuine GM 4 pin module fails, you can switch back to points and move on down the road.....note, without a ballast resistor it'll be harder on your points but it'll get you to a parts store and you'll be back on electronic ignition likely long before cratering the points.  A fine emergency back up, just the flip of a switch....

 

As you used relays to take the amp load off your headlight switch (you did didn't you?....shame, shame if not, safety first, you don't want a fire.....) you use this system to take the load off your points.   Points should last as long as the rubbing block and since you remove the ballast resister (which limits your 12-14.2v- ground power supply to 6v after start up) your new 12v coil will be saturated at double or more voltage full time.  e.g. the function of the ballast resister is to allow full voltage for start up and then reduce to 6 or so volts for running in order to keep the points from burning up.)

 

When done, you have all the benefits of a powerful 12v-14.2v- ground ignition without the cost of an HEI, the difficulty of revamping a points dizzy to slant 6 electronic, or the potential and oft complained of failures of the Pertronix/similar style conversion units.

 

Safe driving....

 

http://gpzweb.s3-website-us-east-1.amazonaws.com/Ignition/GPZheiModForPoints.html

Edited June 22, 2023 by Sharps40

[Adam H P15 D30]

Make sure to read carefully, the HEI module will fire when the points close instead of opening.  This will cause to rotor to be out of phase with the cap.  I tried this once and built a little inverter inside my (now unused) voltage regulator.

 

It worked but in the end it was easier to convert a slant 6 distributor and much less complicated.

[Adam H P15 D30]

Oh and I used the 5 pin on one of my old builds with a boost switch.  Worked great at retarding the timing over 10lbs of boost. 

Also works well when connected to Nitrous.  Great little module!

[Sharps40]

yes, inverted is required to operate points. Very simple as the component types and locations are specified in the schematics.  However, for some, modifying the mechanics to slant 6 is easier and I understand.   In any event, lotsa ways to skin the cat.  

 

Nifty idea to stash the inverter in the old regulator pack.

Edited June 22, 2023 by Sharps40

[Young Ed]

Not sure where you got the notion that the /6 dist conversion is difficult. I had mine converted in about an hour. The trickiest part is sanding a few thousand off the OD of the /6 dist so it fits in the flathead block. Beyond that everything else is just dismantling both and swapping over the drive.

[Sharps40]

Perhaps it's not difficult.   But it does provide options for folks that don't want a permanent change or don't want to modify a good original distributor, etc and it's potentially less expensive.

 

I posted as an option, not really looking to debate an opinion of what's easy or hard.

Edited June 28, 2023 by Sharps40