Maybe this is a stupid question, but I'm trying to set the idle speed on my car using a dwell/tach to get an accurate reading. I grounded the unit and connected the other wire to the green wire post on the ignition coil. There are 3 posts on the ignition coil, 1 where the distributor connects, 1 with a brown wire connected to it, and 1 with a green wire connected to it.

Since I would have to remove the distributor wire to attach the dwell/tach to that post, I left it alone. I also assumed the brown wire running to 1 post was a ground. So i connected my dwell/tach unit to the green wire post. Is this correct?

I was getting a reading of about 800rpm's on the dwell/tach while the gauge cluster was reading about 900rpm. I jumpered the ISV and played with the idle adjustment screw on the throttle body but it seems like I will have to loosen it a hell of a lot to get the idle speed up to 840 on my dwell/tach. Its easy to adjust the rpm anywhere below 800, but it seems to hit a threshold where the idle screw wont do much after that.

Did I connect the dwell/tach unit correctly? I grounded it on the sheet metal shock tower, could this be a weak ground and mess up the readings? If not then maybe the unit is calibrated wrong or something, cuz I turned the screw on the throttle body to where it was sticking up out of the throttle body and the idle speed was still around 810 on the dwell/tach.

 

bump, i know someones connected one of these things before.

 

i haven't used my tach/dwell stuff in years. brown is ground and in the old days the wire running from the coil to the distributor points gave both readings.

if it shows within a 100rpm of the tach in the vehicle it's hooked up correctly.

87951