My only experience with a magneto ignition is in Minneapolis industrial engines that I used for irrigation. I have always wondered how they work on the street in a SBC. I see one for sale in the HAMB parts section. It says ready to run and says it is a locked unit. What does this mean and are they reliable over the long haul on the street? Always wanting to try something different but not wanting to piss away $700. Thanks for any advice.
Locked means no ignition advance . So its more for running in a certain RPM range mostly. Generaly high RPM like a sprint car , drag boat , drag car . It will run on a street car but not ideal at low RPM if timed for high rpm. These days your not going to gain much if anything and might loose compared to a high-end high output electronic ignition at a much much less cost. A mag is nice for its simplicity. Most have no external coil . You need one wire to go to a single swith then to ground . They look cool but do not give much if anything to modern stuff . I ran them in drag boats , sprint cars . If your getting a mag for a street car your going to want one with a built in advance
A locked mag has no ignition advance. Mostly race applications. An advance plate can be installed and is useful on the street. They come in 7 degree and 12 degree (mag degrees, so 14 and 24 engine degrees). If not converted to rare earth magnets they require periodic charging. Most engine elctronics are not compatible. Need a timing box to time. But make a nice hot rod ignition if you get up to speed with them.
For something that's mostly or only street driven it's hard to beat a distributor with both mechanical and vacuum advance. https://www.jalopyjournal.com/forum/threads/hot-rod-technical-library-basic-ignition-systems.983424/
also be aware that while they can be very reliable, if they do fail on the road repair is more involved than with a more conventional ignition.
The members have covered all your questions well. I will mention one other thing, the replacement parts (cap, rotor) are not corner store available and cost more. You have to want the unique look to put up with the issues. Also a cable driven tach could be part of that 'look' and again is going to be more than a regular 1-800 part.
Even with the advance plate, that will make it easier to start, any ignition with mechanical advance will consume more fuel than a vacuum advance. Magnetos (especially the Vertex type) are my favorite in vintage race engines, I have spares for both of my race cars.
Tanks for all the information. Makes it an easy decision. I did give the Joe Hunt mag lookalike that Speedway sells a try in a blown Flathead 32 roadster. I think it was the 4th one that finally worked and kept working. Car went to Portugal 10-12 years ago and I have heard nothing since I put it on the transporter..
Am I missing something here? With a street driven car with a proper tune-up and timing curve, I've always ***umed you'd end up with improved drivability and fuel mileage. Maybe I'm misreading your post ? ? ?
The difference is a magneto has no vacuum advance to help with fuel economy when cruising along at 70 mph and 18” of vacuum for example. Many here say they do just fine without it but I say they are not optimizing their tuneup.
Well said Larry, I have one of the best engine builders as a friend, he knows compe***ion and optimum street performance and mileage. He is big on vacuum advance, for the street.
It's absolutely correct you are leaving one tool on the bench running a mag on the street due to no vac advance. If you are running 4 or 6 carbs and looking for a certain look you need to be realistic about how many areas you take some risk before you are just fooling yourself. Many times I tell myself that just because you can, doesn't mean you should. Trouble is I don't always listen to myself!
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