HEI (High Energy Ignitions) are solid state, the only moving parts being the vacuum advance plate and the centrifigul weights. When converting to an HEI ignition, REMOVE the old ignition wiring circuit, which consisted of a thermistor wire (increases resistance with heat) and runs an entire new circuit using 12 gauge wire from a fused source. The HEI requires a FULL 12 volts all the time. The connector on and HEI distributor has a connector for a tachometer also, so you can install a pulse type electric tachometer. NEVER remove a plug wire and start the car. All the plugs must be grounded or alse you'll make the internal module fail. Be sure to isolate wires #5 and #7 properly to prevent crossover firing. Bob Johnstone rjonst@www.gsdi.org Dec 2001 +++++++++++++++++++++++++++++++++++++ A weak spark will let the flame go out under pressure and resume running correctly when the pressure is off. Check all the plug wires with an ohm-meter to see if a few are drastically higher than the others. One possible problem that can hurt an HEI is that the screws holding the coil are sometimes too long. Some coils were made with fewer steel laminations and were therefore thinner. Using the older longer screws will result in cracking inside the cap when the screws are tightened. Between the cap terminals, inside the cap, will be four almost invisible cracks with four well-grounded sharp points to attract the lightning-sparks to ground whenever the cylinder pressure increases the resistance of the spark plugs. When you step on the gas the cylinder pressure goes up, the spark may decide to go.thru the easier route. When you let off the gas, the spark gets good again. On older ignitions, a bad coil wire can make the engine weak like that. A common mistake made on tuning up an HEI is leaving out a ground for the coil and then ruining the coil through internal arcing. Even after curing the grounding problem, the coil will never be the same again. There is supposed to be a ground from the coil laminations to the center plug-in termnal. Often during a tune up, the ground piece is left inside the old cap that is tossed away. The confusing part is that all HEI coils have a black ground wire that is held to the coil case by one of the mounting screws. That grounds the coil windings to the laminations (coil case) many people see that and think they have it grounded. There has to be ONE MORE ground to connect the coil case to the engine or ign grond, either a flat strap that the coil sets on top of and runs to the middle cap terminal, OR another very short black wire that runs to the middle terminal. If the coil case is not properly grounded to the middle plug-in then the coil will arc internally and eat itself up inside. Even after fixing the ground problem the coil is a weak one from then on. Replace the coil and use short screws. Check the coil ground. Sometimes when an HEI has been internally sparking it will weld the advance to the shaft and need to be worked loose again. Improper timing or timing not advancing properly will leave an engine quite weak DJLevesque@webtv.net (David Levesque)