Another Electrical Problem

[jrdv]

I put a skip white HEI and a new internally regulated alternator with a wire conversion kit from LMC. I also installed a new factory tach.
The first thing I noticed was when I start the truck (69 GMC 4x4) the tach will spin until the motor starts.
The tach and voltage gauge both jump when I touch the brakes.
I have a battery drain related to the alternator.
My main problem is that the motor will die when I hit bumps in the road.
I crossed a cattle guard last night and the truck died. It will not start, but I have power everywhere. There is 12.5 volts to the distributor, but no spark.
I haven't check the coil yet.
My question is whether there might be something simple that is causing all these problems?

Thanks
john

[JayDubBlazer]

I'm sure somebody will chime in but do a search on the HEI modulator. Those tend to go out and cause problems.

[dwcsr]

Sounds like you have something that needs tightening. maybe a ground wire or some other connection

[sjarrett71]

Sounds silly but check your starter and solenoid. Also the wiring to it.