Would it be safe to say that in 68 on a fully optioned car that the maximum amp draw on the alternator would be less than 55 amps since that is the highest amp alternator that was available for a 68? I'm trying to determine what the max amp draw on my non ac car with power top would be before adding stereo components. I asked American Autowire who manufactured all of my harnesses how many amps my alternator wire could handle and they said +/- 80 amps. Thinking about installing a 100 amp externally regulated alternator with an 80 amp fusible link on my alternator wire. From what I have come up with, my max amp draw for stereo will be +/- 52 amps. That would be at maximum output which will never happen. If the stereo was at it's max, and I have an 80 amp fusible link on my alternator, would my car be able to function on 28 amps? Also, anything wrong with running the power wire for my stereo components from my starter solenoid instead of the battery terminal? I don't want power wire to be visible.
I would think a minimum of 85 amp alternator with the proper size wiring should be sufficient. Also add more ground wires of proper size. Ohms law is your friend.
I have just bought a Powermaster 17294, 100A max, 70A on idle, 12Si internal regulator type.
Fitting it and any upgraded cabling is a project for next year.
The electric fans and upgraded H1/H4 headlamps make waste of the 37A from the original '67 alt. With just the parkers my power audit came up with ~35A, without stereo or sub included. Lowbeams take it to ~43A.
The radio's spec is 10A max... the sub (I havent got behind the panel in the trunk to look at type/specs... but assuming 20A average, and depends heavily on content.
I have no idea what the distributor draws when engine running.
fwiw ...after killing an expensive (in Oz) Redtop I now have a 83Fd supercapacitor hanging across the Yellowtop to limit the impact of multiple starts on the longevity of the battery ... 9months in and working fine... maybe black magic and only time will tell how effective it is with the battery.
Your fans are definitely the largest power draw, most likely the same ones I'm running. I have the 140 amp Powermaster 67294. Seems to keep everything nice and bright, I don't have a radio or sound system, couldn't hear it if I did unless the engine was turned off. Would be nice for those long waits at the ferry terminal. though. It would be interesting to put an ammeter on and turn things on one at a time just to see what the draw actually is.
No, what I did was remove all the under hood wiring and make up my own custom harness. I bought a bunch of good quality wire, terminals, relays, breakers, fusible links, solder, heat shrink, etc. and wired things the way I thought it should be. I have added relays for the starter circuit, ignition, horn, headlights, and fans. I put in junction blocks to feed the circuits and reduce voltage drop and eliminated the regulator and horn relay. I crimped then soldered then heat shrink-wrapped every junction and protected every circuit with a breaker and/or fusible link. If one didn't know what a Firebird was supposed to look like under the hood it would/might look normal, but anyone on this site would recognize it as custom. Seems to work.
400bird, the positive battery cable goes directly to the starter so tying your radio cable there would work OK. The only downside would be heat from the engine and exhaust, and dirt/water splashed up from the road. Heat is the enemy of current flow. Might be better to run a wire from the battery under the fender [above the inner fender] to try and keep it inconspicuous. Or perhaps forward to the rad support then down from there. The shorter the wire the better.
An easy way to stay safe with a larger outputting alternator is to run a wire from the back of the internally regulated alternator directly to the battery. This wire combined wirh the factory wire needs to be able to handle the alternator amp output.