tach irregularity

[69.roadrunner]

Anyone experience this?

I was out today and noticed my tach was spiking up and down intermittently. Then was normal again. When it happened i was driving steady at 40mph and approx. 1500 rpm. The engine was steady and normal. All connections are tight

I have a 69 440- running off an MSD 6 al with a msdblaster coil. The tach is a repro connected to the msd box. I recently installed a new Holley double pumper to. Replace an older Holley( single pump)

 

[70rr-brian]

I assume your tach is setup to handle what the MSD is sending it?

 

[69.roadrunner]

It should be. The teach is a reproduction made to runnoff modern equipment. It has been in place for 2 yrs and I never noticed it before