Hello Everyone,

Well, some of you know that I was having issues with the 67 Vista Cruiser and finally figured it out when I went to put my new Petronix ignition in, I found the internal distributor ground was broken.

Surprisingly, the car came with a factory tac. I disconnected it during the install of the Petronix ignition and recently reattached it and the tac does not work. I did searching on the subject and it seems that this should only be an issue for the Ignitor III. I installed an Ignitor II, which from what I read, there shouldn't be a problem. It's not a huge deal if it doesn't work since the tranny is an Auto. but it was kind of cool having it.

Has anyone had similar issues or solutions?

Thanks,
Jim

 

H Jim


I have the same issues. My tach was jumping all over the scale with the Petronix. I put the points distributor back in and now the tach doesn't go over 2000.
Now I have a brand new Petronix on my bench and a tach that doesn't work
Jim

 

I've got a Pertronix Ignitor II in my 66, and the Tach works as it should. The Pertronix replaces the points, but the function is the same and should not affect the Tach operation.

 

Agreed. The tach just needs to be connected to the negative side of the coil. The aftermarket ignition must provide a pulse to the coil that mimics that from the points. This is what the tach monitors. The fact that the tach doesn't work properly with points either indicates that the problem may lie in the tach.

 

Around 1990 I put an MSD box on my 442. The tic toc tach jumped around and didn't read correctly. If I remember right, there was a white ceramic (or something) go between that you needed to add to the system to make the factor tach work properly. I know it's MSD vs pertronix but, it's worth a look.

Found this on a search.

one thing.... that does not get spoken much....

MSD runs significant voltage to the primary side positive side of the coil... much higher than the 12 to 14 volts the battery supplies.. when the negative side is not grounded.. there is enough voltage on the negative side to fry most tachs...

so you never want to hook your tach up to the negative side of the coil like it was...

For what it's worth.

 

MSD is a multi-fire system that will definitely mess up the tach. That is unrelated to a Pertronix, which is simply an electronic replacement for the points. The signal from the distributor to the coil should be the same for both points and Pertronix. That is definitely not the case for an MSD box. Note that the MSD boxes (6A) that I've used have a separate tach output that mimics the single pulse-per-firing stroke of points. This allowed my tach to work just fine.

 

Newer tachs work fine running from the negative side of the coil for Pertronix I/II/III. III has some kind of multi-fire capability, but it's weak enough that the tach doesn't notice, which implies it's probably weak enough that the engine doesn't notice either.

Older tachs can have problems with electronic ignitions. Do a search for "tach filter". You can buy commercial modules, or make your own, e.g.:
http://www.camaros.net/techref/elect...lter/index.htm

 

There are a lot of people running a stock tach with an Ignitor system with no issues. The problem is in the tach or wiring.

 

Thanks for the replies. I can try the filter idea. I installed the ignitor II with the tach off and only recently tried to hook it back up.

The tach worked "ok" before with the points. It wasn't super responsive and seemed to hang up at times but it seemed to eventually read correctly. One thing is, that after I disconnected it for the ignitor install, it didn't go to 0 but stayed at about 2000 rpm. If there is something wrong with the tach, is this something that I can fix or am I sol?

Thanks,
Jim

 

Did you get this tach working and did you try the filter?