Another sad Bendix 3000 story among many over the years. Those double mags must have seemed like a good idea at the time but they've sure been a source of trouble over the years.
Great Plains had some green surplus Slick's that were great replacements for the 4316's and cost next to nothing compared to the normal Slick. These were surplus units and weren't re-buildable but were an excellent deal. Perhaps these are the same units someone mentions are available on eBay. I don't see them on Great Plains's site anymore. Jeff Scott has gone to the double P-mag system so I'd consider that among your options. As I recall he's not absolutely overjoyed with their performance, so check with him. Revmaster has somehow built in a "hand startable" function into their double electric ignition systems. It might be worth looking into just what they've come up with. Your Bendix replacement options come at a good time since the world is full of technological solutions that didn't exist only a few years ago. I'd start with an email to Jeff and see what he has to say. I'm still using the Great Plains electronic ignition system for the secondary plugs and the 4316 mag for primary, I'm overdue (by 300 hours) for routine maintance on the mag and would have done something about this if it weren't such a project to remove the engine from the firewall the six to eight inches required to get sufficient access to the mag. As things sit, the leads coming out of the mag are flush up against the firewall with no play at all. I slid a thin insulator in between them just for insurance. I first gave attention to my Slick being beyond it;s service interval period when I suddenly got some cross-firing when cruising along at my usual high altitudes. From 13.5K my cross-firing threshold has dropped down to around 8-9K. Air (electrical) resistance decreases with altitude when it comes to mags . . . in other words, air more easily conducts electricity down low than when up high. So these days, when I'm climbing through 8K I just switch off the mag. After Sparky found me a new magneto, I also bought new magneto (genuine Slick) leads - something some of us presume last forever. When I changed them on the plane's electronic ignition and on my car ignition I got remarkable improvements. These leads break down over time and start leaking here and there and for all I know, simply build up resistance through use, which would encourage leaking (shorting). I would have already replaced the magneto leads except in order to get to the magneto I have to pull the engine forward a good bit from the firewall and that involves disconnecting some things and it's just a project I haven;t gotten to. Point is, when replacing or servicing magnetos, don't forget to replace your ignition wires, no matter how nice they may still appear to be. You can find very low resistance wires these days that are still well-protected from electromagnetic interference. In other words, just because they have remarkably low resistance, don't presume you'll get static on the radio. The ones I bought are from Taylor - "Thundervolt" I want to say. The ones for the car I bought were just the best Delco's I could find. There's been no static on my aircraft (or car) radio but the VW runs with noticibly more enthusiam. Protecting the car's ECM is another consideration when choosing resistance plugs and wires so I take back any recommendation I might make when using no-resistance wires and plugs on cars with ECM's. I haven't had any trouble with the ECM or radio but that's not enough of a data point to be making any blanket recommendations. In chosing plugs for magnetos - I do suggest you NOT buy resistance plugs. Once magnetos start wearing they don't need the extra stress of resistance plugs. It's to minimize resistance that we buy low resistance wires so buying resistance plugs made no sense. The only purpose of utilizing resistance components is to protect our radio communications but today's ignition lead makers and plug makers have managed to shield their products without increasing resistance these days. I've got non-resistance plugs and amazingly low-resistance ignition leads and my radio is clear as ever. Speaking of plugs, you don't want long reach secondary plugs sticking into your cylinders encouraging pre-ignition. They need to be level with your combustion chamber surface and preferably, the outer electrode needs to be angled away from the center of combustion - not shielding the spark, in other words. Steve had been using some Champions which stuck a good half an inch into the combustion chamber - a real poor way of doing things although I never noticed any pre-ignition before doing my TOH and finding the situation. I think it was Mark that noticed this issue after I'd sent him a picture of freshly-removed cylinder heads. I did quite a bit of researching when putting things back together and wound up buying, for my secondaries, Chamption G-59C with a .30 gap. For the magnetos, I searched and found (they're easier to find these days) Denso W57ES-V fine wire plugs gapped at .16. I may have gapped them a little closer than what the specs call for since I was being easy on my my Slick, overdue for service as it was. Many VW users will use the normally-called-for NGK 4549 (CR7HSA) but I came across just too many comments on hot-rod articles complaining about how NGK are "junk". There were some other reasons too . . . . the Denso's I chose are a "cooler" plug than the NGK. Anything that can help dissipate heat can only be a good thing, when it comes to VW's. The finewire aspect was an advantage as well. There were other reasons too which I can't recall at this late date and didn't note in my logs. The fact they were hard to find added to their allure. Both brands are made in Japan,. At any rate, the Densos have been top notch. I "indexed" both sets of plugs, the Champions with their long reaches requiring a number of copper washers in order to bring their firing surface level with the combustion chamber surface. Both sets of plugs were indexed in such a way as to not allow the outer electrode to shield the spark from the combustion area. My 2 cents. Mike KSEE _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
