Tach Problem

[79er]

My tach will not go past 4600RPM! I did install a MSD pro-billet HEI distributor last year but never took the motor above that due to it was still being broke in. The tach is OK to 4600RPM and below, but once it gets to 4600 it stops moving and the motor keeps reving. A real pain when Drag Race because I now can manual shift the gears or let it do it for me. My question is it the tach most likely bad or the electronic sending sending unit on the distributor goofing up? Has any one else seen this problem?

 

[Jack]

Hmmm?

Since the distributor provides ignition support above 4600, it seems the problem would not be in distributor. Do you also have an MSD ignition amplifier/spark box? You might try this one on either MSD's Joe Lapille @ jlapille@msdignition.com or Nelson Specialties' Nelson Crozier @ info@nelsonspecialties.com ... they're both top-flight MSD experts.
JACK:gap