Trigger weel diameter

[Twentyover]

Hiya guys. Think my question would be best put in the ignition section, since it actually has something to do with ignition.

A bit of background- A compadre and I are putting together a couple Ford 2.9l Cologne V6 engines for what once was SCCA GT-2 racing. We are both running variants of carbs- Me, a Holley on a modified Offenhauser dual port initially designed for a 2.6 Ford, he’s running a trio of IDA’s. We’ve both been working on how to fire the ignition, and I think I’ve settled on a crank trigger running a MegaJolt Light using parts from a Ford EDIS system. It seems to be much more economic than the Electromotive system, and still looks like it can provide good ignition.

I’m currently collecting parts for the build (I’ve got forged pistons, ported World Heads w/ big springs and titanium spring retainers, cam, ATI balancer and am working on an aluminum flywheel.

Question is on tone trigger wheel diameter. I’ll be running a small diameter BBC crank pulley bolted o the balancer, and I’d like to put the triggerwheel between the pulley and the balancer. The outer ring of the balancer is 6.325” diameter, I plan on running a small diameter crank pulley (smaller than the balancer.)

Now my question. How much abouve the height of the balancer ring do the teeth need to project to get a good signal to the crank angle sensor? 1/8”? ¼”? a foot?. I’ve been trying to find an answer on this and I’m pretty much drawing a blank. The only car I have with a crank trigger is an old explorer and it’s not much help.

Thanks in advance for your help

[Twentyover]

No takers? No one have ever installed a crank trigger ignition?

[sccacuda]

Depends on what your using as a trigger? 36-1 or 58-1? The 36-1 can be a smaller diameter, 6" minimum. 58's should be 8-8-1/2" for correct resolution. So the size is determined by resolution accuracy. The valley of the tooth could be flush with the outer diameter of the balancer, but i'd want at least an additional 1/8" to prevent false triggering. That being said, just buy a damper with a tone wheel. http://www.atiracing.com/products/dampers/damperparts/trigger-shells.htm

[Twentyover]

I want to run a 36-1. Already have the ATI shell (6.32 diameter w/BBC pulley pattern). Planning on placing the trigger wheel between the shell and the pulley (this is a high rpm application, so I'm running the smallest BBC single V pulley I can find). i was thinking I would need to be at least 7-5/8 " diameter to prevent false or no trigger, you're suggesting I can go as low as 6-3/4"? How about we split the difference and call it 7-1/4" so I'm proud if the dampener shell by 4/10"? I'm really guessing here.

[sccacuda]

The thickness of the tone wheel is important for flex. The diameter for accuracy. I would think a 7-1/4" would work fine. If your talking 8K plus on RPM, I would go thicker than 1/8". Really need to sandwich this thing to cut flex, or simply buy the front shell I linked for your balancer! Flex not an issue with that.

[Twentyover]

Thanks Craig, you've been most helpful. I've asked both Autosport Labs and DIY Autotune, and they have been mute on the topic.I am planning on a 1/4" thick plate sandwiched between the balancer and crank pulley