Dual mag replacement

[rjcthree]

Guys, I have picked up my core for rebuild, a first-run O-320-H2AD. It is as good as I could have wished for. But that's old news.

I read somewhere that the Bendix 3000 series dual mag can be replaced by a 1200 series impulse, assuming that the second ignition source was an EI. That's my plan.

Having searched this forum and goggling for a half hour, I can find the reference. ANybody have any info or ideas?

Thanks, Rick 90432 - itching to tear down the core.

[mannanj]

Rick:

If the H2AD is like my IO-360-A3B6D, (D being the common denominator), the gear driving the mag and impulse coupler had a "pilot shaft" that fits into the rear of the crankcase. The the pilot shaft is oiled by a small bleed hole.

You can fit the gear and impulse onto a couple of older Bendix mags with the proper dash number. I think I still have that info at my hangar.

If you arbitrarily install any ole mag into that position, you will have a miss-match of depth of gear mesh of approx. .100 to .120 inches making it necessary to machine off .050-.060 from the accessory case and the same amount from the face of the mag to achieve optimal depth of gear mesh.

The other problem is---how do you stop the oil pressure loss from the bleed hole in the rear of the crankcase where the pilot shaft used to be?

Another solution is to disable one half of the original mag and run the electronic ign. for the other plugs.

It's a problem any way you do it. I chose to run dual mag for now and later when the bank account recovers from building, install the 3000 drive onto the proper 1200 series mag and use lightspeed with the ring gear pickup for the other set of plugs.

[RV8RIVETER]

Rick

I have an IO-360A3B6D so I have done some research along the same lines. I assume our engine workings are the same, but I may be wrong so that said... Yes you can install a single but there is only one option that I know of. Told to me by Jeff Rose of Electroair was to rebuild a mag with strategically chosen parts from the dual mag, of course only an experienced shop for this. The reason is the dual mag turns in the opposite direction. Below is a copy of an email exchange with Travis Loofbourrow who did this on his and was kind enough to share his info.

I also researched the history on the dual mag and it has been pretty reliable. The only issue was when people would adjust, replace it and reuse the same star washers and they started to slip. This resulted in an AD to use new hardware. So I decided to go ahead and fly the first couple hundred hours with the dual mag and then will be switching to crank sensor electronic ignition. Just haven't decided on dual or single.



Wade,

The Part # for the Bendix 1200 series mag that will fit on the Dual mag engine is part #10-34936 5-3, and the Stock # is E S4LN-1227. I couldn't seem to find any of my paperwork for which shop I got it from, but I do recall it was one up in Oklahoma. With the stock # & part #'s you should be able to find a place to build you one up. Keep in mind that you do have to reuse the dual mag drive gear with it's rubber drive dampeners from your original dual mag for this conversion since they both use the same drive type.

By the way, the single Bendix mag will cost you around $700 or so...they aren't cheap due to the fact that all the parts for them are virtually twice the smaller type mags, but none of the smaller ones have the same drive type that the dual mag has. You might be able to trade in your dual mag to reduce that cost slightly.

Hope this helps you out!

Travis

[rv9builder]

If you replace the dual mag with a 1200, do you still need Van's special motor mount for an O-320-H2AD or can you use the standard O-320 Mount?

Thanks,

[gmcjetpilot]

I don't know the two mag in one config that well, but what about using a Lightspeed hall effect or P-mag in the one mag hole and a crankshaft/ring gear trigger (light speed) for ignition #2? Just a thought.

Might not fit but if it would than that would solve the problem.

[Vern]

You still need the special mount because the engine has a different backside shape. Model 2000 mags should be replaced with 3000 for better safety and reliability. Disabling one side is a simple way to add a single EI.

I have the 3000 on mine. Paid $700 for a fresh yellow-tagged one.

My engine is the easiest starting light plane engine I've ever flown, so do not be in a rush to discard the dual mag.It has given reliable service for many years on a very popular airplane-C172N. The money might be better spent on other goodies.

[gmcjetpilot]

Originally Posted by Vern

You still need the special mount because the engine has a different backside shape. Model 2000 mags should be replaced with 3000 for better safety and reliability. Disabling one side is a simple way to add a single EI.

I have the 3000 on mine. Paid $700 for a fresh yellow-tagged one.

My engine is the easiest starting light plane engine I've ever flown, so do not be in a rush to discard the dual mag.It has given reliable service for many years on a very popular airplane-C172N. The money might be better spent on other goodies.

Good points all Vern. Have fun make it simple.

[mannanj]

I'm not that familiar with the 0-320-H2AD, but my I0-360-A3B6D fit just fine in the Van's standard I0-360 engine mount. Best to Call Van's and double check tho. (Oops, disregard calling Van's. Just read Vern's post, and knowing Vern; He's right!)