Originally Posted by jim lockwood

You definitely need either a ballast resistor or a coil that functions without one. Mount the resistor on a stand off, so it gets plenty of cooling air around it:




It may pay you to also go beyond the "get'er done" approach of just doing the minimum needed to make the engine run. What if something goes horribly wrong while your engine under test is running?

You'd want a kill switch for all the electric circuits. This needs to be right at the battery. If you have an alternator on the engine, the switch needs to be a two-pole, single throw type so you can interrupt not only the battery lead but also the alternator output:



You should also consider adding a master circuit breaker (silver rectangle, left) and individual fuses for the various support circuits, like gauges, ignition, starter solenoid:



And, in my opinion, most importantly, always add a fuel cut off valve:



Go the extra distance to include these things and, if something goes really wrong, you've got a chance to do a safe shut down.



Jim