Help I am running a S/W elctronic tach on my 455. This tach is the most unreliable thing I have ever seen. It will jump from 600 to 4000 rpm while my engine is idling. It completely spins around during cranking. It was originally installed with my 430 and point distributor. Now I have a 455 with MSD billet HEI and Blaster coil and I get the same thing. Anyone have any ideas or fixes? I emailed S/W and they said it can't be the tach. I also removed it from the car and took it to a guage shop whosaid it was working fine and calibrated perfectly. At wits endo No: o No: dukec
Where are the wires connected? Negative coil terminal - green wire Ground - black wire I guess the colors would differ a bit depending on brand of tach.
Wires Adam I used the supplied S/W wiring diagram and hooked them up as they indicated. I have also checked this out many times since to no avail. I also forgot to mention that the car was rewired by a professional restorer and myself when the new engine went in early this spring - nothing in the operation of the tach changed. It is still messed up. I asked S/W about a signal filter - they said they did not have any. Does anyone have a recommendation as to what might work? Thanks
MSD has a tach filter I believe.. My hoodtach started to behave strange sometimes with the msd HEI probillet distributor, and after I used the 'filter' they included in the distributor-box, it worked fine again.. Otherwise try another distributor if you have one, and check the tach again..
dukec, Some aftermarket Tachs require the use of either a conditioner or amplifier to work correctly. Most guys have no problem with an HEI and factory tach as long as the tach lead is connected to the tach terminal at the cap and the tach is grounded correctly in the dash. Year One sells a conditioner or an amplifier for 89.95. According to their catalog Stewart/Warner tachs need the conditioner for points or HEI use. Part # for the conditioner is HP28, and Year Ones phone # is 1-800-932-7663. Hope that helps.
