New Tach readings off 300rpm after MSD upgrade

[BensRat]

I am using a new 68 Camaro tic toc tach and complete new MSD system
(#6530 box, 8920 adapter, msd coil & wires, and msd billet distributor). After installation my tach appears to be off my 300rpm. We compared it to the MSD 8963 shift light as well.

Any suggestions?

[msdtech22]

Quite honestly, I would set a rev limit in the MSD ignition at a low rpm, such as 3,000 rpm or so. I would then run the engine up to the rev. limit and see if it limits at that rpm, all the while watching the tach. I would trust the MSD ignition, more than I would the tach.

Does the 8963 light at the programmed rpm?

Is the tach adapter wired into the tach output along with the shift light? If so, are you using a PN 8911 tach splitter? When running multiple items that require a tach signal on the tach output, we STRONGLY suggest using that tach splitter.

[BensRat]

Hi,
the shift light does light at what we believe to be the correct rpm, but cannot verify 100% with tach being off

We are not using the 8911...i will order one today and report back.

thanks

[msdtech22]

Anytime we can be of assistance.

[BensRat]

after installing the splitter, my tach still reads high. I also ckd the voltage from the tach adapter and it is within range. I guess the Tach i bought is the issue even though the manufactuer claims they never had one read off by this amount. Not sure if i mentioned it, but it is a 68z28 OER Tic Toc Tach w/6000rpm redline tach.

[msdtech22]

As I said before, I would trust the ignition and the shift light as they are both digital units and are usually within 2-3 ropm of the programmed specifications when the tach output or rev. limiters are concerned.

I would suspect a tach issue.