High voltage readings

[oldcarnut]

I've been trying to chase down a stumbling misfire type issue on another thread topic. Been through different carbs, ignition MSD and Firecore sys, fuel supply, etc with no results yet. I decided to check voltage to coil and got some funky readings to me. For background info. I'm using a powermaster alt and wiring redone, voltage gauge, direct wire cable from alt to battery. Dash feed wiring from battery to a custom gauged dash with configured wiring for using relays in under hood to operate lights and etc.. Ignition is back to Firecore sys with direct switched power feed to coil, no resistor or box to go through. Stock voltage regulator used. With engine not running and key on, I get readings about 12.3v across battery posts, coil wire, and alt battery feed. Cranked up I'm getting 15.5+v across battery posts and coil feed wire source. Wild fluctuating readings of 17-19 v at coil pos+. post. How is this possible and will it possibly be a source of my stumbling bucking misfire type issue from too much coil voltage? Just exploring anything for a cause at the moment. I rechecked numerous times with multimeter and duplicate it.

[b5blue]

I'd try swapping out a battery, 12. anything is a bit low.   

[oldcarnut]

I think I got it resolved for now.  I swapped out the coil and the problems seemed to dissappear right away. Engine fired right up, voltage at coil feed wire 14.6V and alt back stud.  I still need to place a 0.8 ohms coil feed wire resister to drop the voltage from 14.6 to 12.  The one I had on hand to temporary use was 1.7ohms and takes coil voltage down to 6v but it still allowed for testing the MSD Blaster 2 coil and running up the road for a drive. It ran great. So I'm guessing that the internals of the Firecore supplied HEI coil was malfunctioning and feeding voltage back out the +terminal into wire harness causing the voltage spike and misc. stumbling/misfiring issues.  Time will tell.  Traveling to the UK tommorrow for a few weeks so it'll have to wait.