Bosch ZR4 Dual Spark

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Model T Ford Forum: Forum 2015: Bosch ZR4 Dual Spark
Top of pagePrevious messageNext messageBottom of page Link to this message  By John From Oregon on Monday, April 06, 2015 - 06:46 pm:

I would like to eventually install this mag on my car so that I can use the Rajo BB to the fullest extent.
How should I make the wiring harness?
What gauge wire should I use?
Can I use the stock generator?
Thanks!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis in San Jose area, CA. on Monday, April 06, 2015 - 07:15 pm:

That looks like a Matco cross drive mag adaption. I can't imagine what kind of wiring you need...other than a ground wire to kill the mag. Of course spark plug wires. If you have a BB then you don't have a dual ignition system...but that doesn't make much difference.
The generator has nothing to do with any of this.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis in San Jose area, CA. on Monday, April 06, 2015 - 07:19 pm:

Oops...I didn't notice the dual spark feature...that should be fun working that out. I'm not sure what that is about. By the way..that Matco is set up for a generator engine.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Milton,WA on Monday, April 06, 2015 - 07:38 pm:

I understand a ZR4 2 Spark dual fires 8 plugs.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Clayton Swanson on Monday, April 06, 2015 - 08:11 pm:

it only has 4 towers on the cap correct? dual spark is so you can start on battery, and switch to mag like a normal T. is there 2 terminals on the point cover? if so, one is ground to kill it, and one i believe is for a battery connection.


Top of pagePrevious messageNext messageBottom of page Link to this message  By tim moore, "Island City" MI on Monday, April 06, 2015 - 08:13 pm:

Yes that Bosch ZR 4 twin spark magneto is appropriate for a Rajo BB twin spark head. Yes with that cross drive front plate you can use a generator. Wires are easy, just use the normal Model T spark plug wires with the brass plate for the front studs and on the top connections strip off the brass plate, strip off the insulation but leave 1/2" of internal wire and bend it back over the insulation and push it in or use modern dist. cap metal connections.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, April 06, 2015 - 08:55 pm:

What I am curious about is how it is connected internally.
Tim, you seem to be knowledgable about this mag;
1. How many sets of points does it have? One or two?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth from NC on Monday, April 06, 2015 - 09:59 pm:

Les: this is a good article see about the ZR4 two spark.

http://theoldmotor.com/?p=26928


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, April 06, 2015 - 10:46 pm:

So their description is consistent with my thoughts. The dual plug version fires a plug from each end of the "high tension " winding, rather than having two high tension windings as some have thought


Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis in San Jose area, CA. on Tuesday, April 07, 2015 - 09:19 am:

Unless it is hiding behind the large drive gear in the photo...you are missing the drive tang that screws onto the cam at the cam gear.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brian Sullivan, Powell WY on Tuesday, April 07, 2015 - 09:46 am:

If that is a twin spark, dual ignition DU, it is a rare beast indeed. Below shows the aforementioned drive nut, and a wiring diagram for the dual ignition.






Top of pagePrevious messageNext messageBottom of page Link to this message  By John McGinnis in San Jose area, CA. on Tuesday, April 07, 2015 - 09:56 am:

Sure doesn't look like the magneto fires 8 plugs.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Clayton Swanson on Tuesday, April 07, 2015 - 11:04 am:

all the wiring diagrams i've seen are using the real bosch switch and coil which is expensive stuff. why wouldnt the stock T switch and a 6volt coil do the same thing? i have the du4 with 2 terminals on the point cover


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Tomaso - Milton,WA on Tuesday, April 07, 2015 - 11:18 am:

John - notice that 4 plug wires come out the front (black knobs) and 4 more out of the top.

I run a BB and 20 years ago when I was building the engine, ZR4 2 spark duals were not common and the one I did find was $2400 reconditioned, a bit over my budget at the time so I went with a Mitsubishi distributor that fires all 8 plugs.


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