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Crank trigger with 4 magnets.

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Hey everyone,

Ive setting up a config for a small block chev running an M880, its using an MSD trigger wheel with 4 magnets and individual ls coils per cylinder.

before I spend too much time on it has anyone had good success getting accurate ignition timing with such low crank resolution?

thanks in advance.


No, you will need more triggers for MoTeC. I would suggest you fit a 36-1 external trigger wheel, and a single pulse per rev cam sync signal in the distributor.

Thanks David,

That was my thoughts too, I feel bad for the guy he’s been lead up the garden path on a lot of parts he’s bought for his car/build.

Might be him failing to do his own homework and/or not understanding what he actually needs and getting confused?

There are MANY kits for converting the SBC, it would probably have been much easier, and cheaper, for him to just have opted for one of those.

It could be run as a One Tooth Per Firing setup (Mode 0), but your timing is only updated once every 90° of crank rotation. It would be much better to fit a 36 or 60 tooth missing tooth trigger wheel if possible.

I’ve found a 12 magnet replacement. That would be better without making big changes. The car is already together and I don’t think he’d be keen on re doing it.

That will work better.

Thanks Steve I’ll give it a go. I might have to break your balls again for some help.

dash and keypad you helped out with works great.

Holley offers 36-1 trigger wheels in common SBC trigger wheel diameters. Fitting one of those with a matching sensor (IIRC there is direct replacement hall sensor available from Holley/MSD that threads into the same bracket as the flying magnet trigger setup, or go for one of the full kits and the existing trigger wheel kit can be sold complete offsetting the cost of the new parts, and not have left over parts.

Thanks for that. I’ll see if they will fit, looks like 7.25 inch is the smaller size. Hall effect would be nice too.

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