Sunpro tach bouncing

[wagonman]

just got done with the HEI conversion. Went from a GM 990 module and an older oil filled coil to a Pertronics 60103 coil and Accel 35361 module. Now the tach bounces what am I missing?

 

[64SF]

I’ll be watching have a similar problem. Bounces and reads high.

 

[wagonman]

I’ll be watching have a similar problem. Bounces and reads high.

Same Sunpro Super Tach 2 ??

 

[Bee1971]

The HEI module is still an inductive discharge ignition system

You just installed a very low ohm primary resistance E coil designed around the Pertronix Ignitor 111 module

Try installing your canister type oil filled coil and see if your Tachometer reads correctly , and then

 

[wagonman]

Looking at My own Pic and you can see where the yellow tach wire is on the Coil tower and boot. Moved it and still the same.

 

[wagonman]

The HEI module is still an inductive discharge ignition system

You just installed a very low ohm primary resistance E coil designed around the Pertronix Ignitor 111 module

Try installing your canister type oil filled coil and see if your Tachometer reads correctly , and then

Will have to source another coil as the old one is junk.

 

[Bee1971]

Any old 1.4 - 1.5 OHM primary resistance oil filled coil

Your just doing a simple test first , then

 

[Gsmopar]

Define “bouncing.” I’ve had a bad plug wire cause the tach to bounce.

 

[kiwigtx]

Define “bouncing.” I’ve had a bad plug wire cause the tach to bounce.

Needle fluctuating incorrectly according to RPM of engine is how I read that.

You may be experiencing "High voltage induction" due to the tachometer supply wire being too close and /or running almost parallel to the HT lead off the centre of the coil.

This is a condition which can be cured (or disproved) by simply running the wires away from the HT cable, and as a test you could wrap the wire in foil. Normally I would run a twisted pair with a foil screen to really be sure of getting rid of that problem. I have done this before on a bespoke ignition system in a Hot-rod.
Same problems can arise when running a Hall-effect speedometer and too close to ignition cabling.

 

[wagonman]

It has newer plug wires on and the engine runs fine, I will give the foil a try and also the twisted wires also wrapped.

 

[Don Frelier]

 

[Don Frelier]

But seriously if you install a shielded cable with a drain wire.
Cut and heat shrink at the coil end and then strip out and ground near the tachometer.

 

[wagonman]

But seriously if you install a shielded cable with a drain wire.
Cut and heat shrink at the coil end and then strip out and ground near the tachometer.

Thanks Don, after doing some research I did what you suggested with some foil and a drain wire wrapped in electrical tape and heat shrink. It worked thanks again.

 

[Don Frelier]

I have a bunch of 9463 let me know if you would like some.

 

[wagonman]

I have a bunch of 9463 let me know if you would like some.
View attachment 1126443

Sure I will take what ever you think is best. PM Coming.