Has anyone done a Chevy 350 SB mod?

[Timebender]

If so, I have a question, specifically regarding the alternator setup. I got mine with the 350 mod which was done but the original owner (two owners ago), and my alternator is shot. So I bought a new one. Problem is, the alternator on mine had 3, not 2, tabs (aside from the post to connect the battery). One wire was connected to the sensor tab, which runs back to the positive post. Another, which looks black, was plugged into the number 3 tab, vs. #1 (which is the battery indicator light). So I googled it and could find no alternator like it, and finally called a automotive electric shop to see what it is. They basically said whoever did the conversion was looking for a higher amp alternator, found this one, which really belongs to a boat, and it fit kind of. That tab is for a stator, and could be used to send a signal to my external tach (yes, there's an external tach, and yes, I now know about the Dakota Digital box that will let me use my built in tach). But I do know the tach is getting a signal from the distributor (HEI distributor with a tach signal). When the tach wire was disconnected, no tach reading.
So now I'm trying to guess where the black wire might go. Aside from cutting all the wire wrap...
Does the DeLorean have a stator wire off its alternator, though I don't really need one anymore , that I can think of? And still, I need to find the wire that would have run to the dash light..

[Josh]

pictures would help alot, as this is a one off setup.

The requirements for a Delorean are the main power feed (obviously) and the battery light.

Gm 3 wire:
Large lug - Power feed
#1 - Battery light
#2 - Power Feed

As for the tach signal a Hei distributor should be able to handle it. If the distributor did not have a tach signal some applications would pull from the alternator with the additional terminal you describe. But not both. So since you are no longer getting a signal it seems like the tach signals needs to be migrated back to the distributor, or at least to double check this. Maybe it is in some strange series circuit that is not damaged with the missing connection.

When you have a modified car like this nothing is straight forward, especially if you did not do the work yourself!

[Timebender]

pictures would help alot, as this is a one off setup.

The requirements for a Delorean are the main power feed (obviously) and the battery light.

Gm 3 wire:
Large lug - Power feed
#1 - Battery light
#2 - Power Feed

As for the tach signal a Hei distributor should be able to handle it. If the distributor did not have a tach signal some applications would pull from the alternator with the additional terminal you describe. But not both. So since you are no longer getting a signal it seems like the tach signals needs to be migrated back to the distributor, or at least to double check this. Maybe it is in some strange series circuit that is not damaged with the missing connection.

When you have a modified car like this nothing is straight forward, especially if you did not do the work yourself!

Yeah I figured someone at some point moved the battery light to the 3rd tab (not the power feed lug), and when i got it back from a certain shop, the wire from the sensing tab, #2, was disconnected. Why I don't know. So I had to figure out where that went, which I did when I found that it was a hot feed, did some Googling, etc. But the black (which might be black/brown) was hooked up to the stator tab (#3), and there wasn't anything going back to connect to the battery light (not hooked up or even present).
Thus since I got the car back from the shop, it's never been charging, and most likely it damaged an almost new battery.

So I got a nice new alternator today, 110 amp, with connectors for the battery light, sensor, and even one to the ignition in case I don't want to hook up to the battery light, or it should just go out and I don't feel like yanking out the binnacle to replace it.

One thing they did mention at the electrical shop - does the line from the alternator run straight to the light, or does it go through one of the relays? If it does, they said the light might remain on but be dim.

And yes, the tach is getting it's signal straight from the dizzy.


Greg

[Josh]

The alternator runs directly to the light.

As for the sense lead, lots of guys just bridge it over from the main power feed. This entirely defeats its purpose. May as well just leave it unhooked, the alternator will behave the same. To hook it up properly you would want to run a line directly to the battery. It will sense if the voltage drops below 13.8V and will adjust the regulator to compensate. If you just bridge it over from the power feed the voltage drop along the wire (and any other devices it is hooked to along the way) skews this reading.

[Timebender]

The alternator runs directly to the light.

As for the sense lead, lots of guys just bridge it over from the main power feed. This entirely defeats its purpose. May as well just leave it unhooked, the alternator will behave the same. To hook it up properly you would want to run a line directly to the battery. It will sense if the voltage drops below 13.8V and will adjust the regulator to compensate. If you just bridge it over from the power feed the voltage drop along the wire (and any other devices it is hooked to along the way) skews this reading.

Interesting - every schematic shows it bridged or jumpered to the line coming in from the battery. I now have a new, small project, but might have to get the D up in the air to do so.

[Timebender]

I got a new 110 amp alternator and hooked it up last night. It came with a pigtail harness, with connections for the indicator light and also ignition. So I tried both (one at a time) to the one wire that wasn't that sensing wire (which I could hook up to the battery but need to get the car in the air). Both did the same - allowed the alternator to charge at 14.3 volts (yay!), but my dummy light never came on, which I'd guess it's burned out. So for now I hooked the ignition wire to the one on the car. If I get a chance to remove the binnacle someday, I'll replace the bulb and see if that wire affects it.

I might need a new battery, as voltage dropped to just above 13 volts with the headlights on. Unless that's normal.

[davidc89]

Does it say 13 volts on the gauge cluster or on your volt meter?

[Timebender]

Does it say 13 volts on the gauge cluster or on your volt meter?

On a voltmeter, it reads 13 (and I forget what now) volts with the headlights on. Off, it reads 14.3.

The gauge itself is slightly above the 13 mark when lights are on, and about halfway between the 13 and next tick when off.

[davidc89]

You should be fine

[Lou and "Boo"]

Wow that must be quick! A 350 sbc.... Wow!

Please post videos when it's up and running!