Add me to that list of guys who never saw an amp chart for accessories. For a quick guess I use the same method that is code standard for household AC circuits: the continuous load should not exceed 80% of the circuits rating, eg: a 15 amp circuit should not have more than 12 amps on it. Gael's info above is close to this spec. The alternator excitation is pretty much nill as once it is putting out it is self exciting as long as it is still connected to a battery, which of course it must be to keep working. An HEI at full boogy probably draws about 6 to 8 amps as a guess based on the 12 gauge wire that is usually recommended for hooking it up.
