I put an LT1 in my firebird and my tach is misbehaving. The tach is fine at idle but drops to 0 during acceleration. The tach reads accurate as long as I am not accelerating. The tach worked fine before, but hasn't worked right since. Please help.

 

When you go changing stuff from stock... all hell can break loose lol... I'd just get an aftermarket tach!

 

Does it have a tach filter on it? little silver can-looking thing with a wire out each end and a mounting/grounding tab.

 

No I do not have a filter, LT1s don't have one mounted on the coil. I have traced my problem to my fan wiring. The wire I used to power my relays is an ignition hot wire from my fuse box(pink/black). My tach works fine when my fan relays are disconnected. I can't drive my car without fans; so I need help isolating the problem. Is there something I could put inline, before the relays, to prevent this. Thanks for the help.