I have a 1970 SS396 Chevelle with the factory tach. The tach works but faster I drive the further off the RPM's become. It does have an HEI distributor. I have asked everywher with no convincing answer. Some say have the old tach calibrated, others say put a new NOS tach in. Either is fine if I'm sure it will solve the problem.

I have fixed several 70-72 tachs that responed like yours with replacing the circuit board. Problem is finding the circuit board. I buy trashed out chevelle tachs and 70's camaro tachs just to get the circuit board.

You can have the tach repaired too.

http://www.tachman.com

Steve'
If I bought a NOS tach from Ground Up or Ausleys would it be just a bolt in with the new circuit board attached?
Thanks for the Help!!!
Ron Szabo

Don't think they have NOS but they do have new replacement tachs that are bolt in's. Don't know if the tach circuit will interchange from new replacement to original. They look the same.