OEM tach with Pertronix

[hemi68charger]

Hey ya'll.
I just installed, temporarily until I get an Ignitor II (you'll be proud of me Mike) in my '69 Daytona. It runs great. But I did notice my tach freaking out a little. Is there something I should be doing to compensate for the Pertronix addition. The difference I've notice is under acceleration, the needle goes way higher than it should be, i.e. shows about 5500 when in fact I know I'm only probably at 3500. Yes, there has been a noticeable change in the responds of the tach post-Pertronix installation. I was thinking of converting the tach to one of these transistorized versions out there.

Thanks..

[mhinders]

I have a billet Pertronix with Ignitor 3 and my 67 tach behaved exactly the same as with the original distributor, i.e. showing readings all over the place.
Just for fun I tested 2 units 67 tachs using a signal generator, which can be set to exactly any RPM desired. In the pic attached you see the tach units A & B. The _2k means the tach is calibrated to show correct reading at 2000 rpm, the _5k7 at 5700 rpm.
The B unit calibrated at 5700 rpm is pretty good, while overall the accuracy is not so good in the original tachometers.
This summer it will be interesting to see if I can get the tach to work properly with Ignitor 3 in my car. I believe my lousy electrical system has contributed to lousy readings, and I hope have that fixed for this summer.

One could think that a multi-spark ignition could increase the rpm readings, but I will know more once my car is ready for the road...

Cheers,
Martin