I finally got the Camaro on the road this past weekend for the first time after 8 years. The Tach is reading way off. At 70 mph it read 4500 rpms. I have a 396, 350 hp factory cam, turbo 400, 3.31 rear gears, 2800 stall converter and HEI. Here's my question. In the attached post Hotrodsrj makes a statement about using quality HEI modules instead of the junk from overseas. Has anyone getting bad tach readings tried changing their HEI module? Did it correct your tach readings? I do not want to cut my wires if I can avoid it.

http://www.camaros.net/forums/showthread.php?t=55361&highlight=tach+readings

Oh yes, '88 MCSS, stock dash tach w/ early HEI (pre-ECM), read 4200 rpm@60 MPH.
Aftermarket tach added and reads right on the money, 3000 rpm@60 mph w/stock tires/gear. This is with a GM module 4-pin inside.

Everett, did you change the module in your distributor and get your factory tach to work correctly?

Unfortunately, no, I haven't had the time to mess with it. I bought a used aftermarket tach from another forum member for $15, clamped it onto the steering column, hooked it up to the TACH terminal on the HEI and been using it ever since.

If I decide to put the filter in, can I put it between the coil and the HEI?

No, goes between the TACH terminal and ground.