Technical Running A SBC on 6 Volts in a 6 Volt Car

I floated this idea a long time ago, but I never followed through. I actually started a thread on this a long time ago, but I was not a nice guy back then. I'd like to start this discussion over.

Is it possible? Can a 12 volt SBC run on 6 volts in a 6 volt car? Why would anybody want to do this? Follow me...

I've got a 1955 Thunderbird. It was fully loaded from the factory. The 1955 Thunderbird was a 6 volt car. That means the power windows, power seat, and all the cool stuff (like the dash clock) all run on 6 volts.

I have a 331 Chrysler Hemi that at some point I want to install in the car. It needs to be rebuilt. I even have the adapter to adapt it to the Ford Toploader that came with this car. The 331 Hemi is a 6 volt engine.

I want to rebuild the Hemi the right way, so I expect it to be expensive. With that said, I've got SBCs in my collection that I also can get going in the meantime.

I think my biggest hurdle the last time I floated this scenario was getting a 6V starter for the SBC.

I really want to get my Bird on the road while I get the Hemi in the shape I want it, so I'm willing to try something different with a SBC until I can make my Hemi dream a reality.

I tried going the Y-Block route originally, but cores or running engines aren't easy to find anymore.

What are your thoughts?

 

It's not easy...the Chevy starter design changed completely when they went to 12v, you can't put any 12v parts in a 6v starter, or vice versa. The 6 cyl 6v starter uses a different flywheel than the 12v starter. So there are serious mechanical differences. You can't just put a V8 nose on a 235 6v starter, it won't fit. And the drive gear is different, and the size of the armature is different, etc.

When I swapped a 55 bird to 12v many years ago, it wasn't very difficult...but I don't remember if it had manual or power windows. I think it had power seat. I used a 56 gauge voltage regulator for the gauges, 12v alternator, and I think 12v 56 starter. Replaced all the bulbs. I think the radio didn't work, so that didn't matter.

 

I know you've seen my post in the past on my 55 Bird. It's not an original car, but I have found a great deal of original parts since I bought it.

I've seen devices that go between the 12v battery and 6v device that are suppose to only supply 6 volts to the device. I don't know how well those work. I'm not sure I want to risk burning the whole car down just to find out either...

 

Use a DC/DC converter

use the 12volt starter and alternator for the engine stuff as @squirrel stated .

and get a 12-6 volt dc dc converter to run the other stuff .

Will need to figure out your amp draw to get the correct one .

 

This won't be a ton of help but I have three thoughts off the bat:

1. Do you really want to run the SBC ignition off of 6V? Could this mean weaker spark and therefore lower horsepower?
2. Converting the car to 12V and leaving it that way with whatever future engine it has seems like a better long-term solution to me. 6V is only becoming more and more obsolete.
3. If you have several SBC's, are they slated for future projects? If cost is a concern, why not liquidate them if they're not needed to pay for the hemi rebuild?

 

I guess that if you don't understand electricity and how it works in cars, this could be pretty intimidating. As others mentioned, you need to understand each part of the car, and what power it really needs. Not just the current load, but also what type of load it is (motors and lights and electronics are all different)

 

You also have a polarity issue

 

Horsepower is not really my concern. I'd run points if I can get it to work on 6 volts.

Converting the car to 12 volts unfortunately looks to be the best solution.

Everybody wants LS engines now. The heads I want for the Hemi cost close to $4K. I probably couldn't get $400 out of my SBCs... Just being real.

 

Instead of $4,000 heads maybe this is a better deal https://www.facebook.com/marketplac...wse_serp:87563e92-5fb1-4edc-bf8c-aaa5098ef5b0

 

While you're at it, why not make it positive ground also.

 

Parts aren't cheap for sure. Even aluminum heads for my 455 Buick would be $3K USD. It cost me $1,700 CAD to have a new set of heads redone last year, with valve springs as the only new parts.

You made it sound like you had a bunch of SBC's. If you could get a couple grand out of them collectively that would go a ways towards getting your hemi built. Just an idea, of course you're free to do what you want.

A stuck engine for $2,900 USD. Yikes.

 

You run 2 x 6volt batteries "in-series" for the starter motor when cranking and "parallel" when running / charging
I did exactly what you're wanting but 24volt to start an 12v running /charging on my Lotus Cortina

You need an extra Ford starter solenoid and a couple of decent relays [70a] and some "creative" wiring

Here is a schematic where I used 2 x heavy duty 12v relays to switch between 12v and 24v [the 24v switch is a starter button]


It has some failsafe features in the schematic.
The button switches the "Neg" relay to disconnect the parallel neg circuit and provides the ground path to the primary circuit of the "Pos" relay.
If that relay fails it won't activate the "Pos" relay. which diverts to the "neg" post to in-series] The 87a post of the Neg relay is a dead open circuit.
This means it is impossible to get "cross connecting" between the batteries [parallel and in-series at the same time]

For a heavy duty starter circuit you modify it by adding a 3rd relay [a Ford starter solenoid] to connect the batteries together in-series.
You disconnect the wire with orange X's
And connect another wire from post #87 to activate a Ford Starter Solenoid which connects the 2 batteries "in-series" [lower red arrows]


I did this on my Lotus Cortina to get 24v to a piss weak Lucas starter motor so it would crank over faster.
Release the starter button and the 2 batteries charged "parallel"
On my Lotus I managed to get 2 batteries to fit neatly inside a plastic marine battery box

 

Could try running two 6 volt batteries in series. Then branch one 6 volt for the body, and run both to alternator/starter/ignition.

 

Kerrynzl, this is what I'm talking about. Yes! Good answer. Good job sir!

 

The one I have is not stuck... I just want the $4,000 heads because they flow better.

 

The 1955 Ford Tbird has a 6 Volt positive ground, the SBC starter is a 12 Volt negative ground. That adds up to 18 Volts. I don't know if the 12 Volt starter runs backwards if you reverse the polarity (my heavy electric motor class was about 60 years ago - mostly 3 phase AC motors). This question also applies to @Kerrynzl's relay solution.

Suggestion: Take a Chevy starter, use jumper cables and apply 12 Volts in both polarities. If the starter spins in the same direction - your solution gets much simpler.

Russ

 

Since the Chevy starter has field windings, instead of permanent magnets, it will run the correct direction if you reverse polarity. The magnetic fields in both the armature and the field are reversed when you change polarity of the battery, but since they're both reversed, it turns the correct way.

 

Clearly, I need to learn more. The last class I took in schematics was 25 years ago.

Can you suggest some reading material to help me remember what I have forgotten?

 

One Caveat!
On my Lotus it had one of those awful "throwout bendix" type starters
With a Chevy starter with a solenoid I recommend a DPST momentary switch for the starter button


One side [2 terminals] activate the relays and Ford starter relay
The other side [2 terminals] takes a feed off the 12v at the starter motor and activates the "S" post on the Chevy starter.
One button controls all functions [You could also do this with another relay ]

 

Years ago, on Heavy Duty trucks, we used to use a series-parallel switch to hit the stater motor with 24 volts and the rest of the electrical system was 12 volts. This would probably require (2) 6 volt batteries. Even though on trucks we used 12/24 volts, I don’t know why you couldn’t make 6/12 volts work.

 

Truckdoctor beat me to it. Series parrallel switch but requires 2 batteries. Seems like a lot of potential issues.
.

 

It works, but not well - one battery is constantly overcharged as the 6V load only draws power from the other and the charging needs to run the charging current to keep up with that through the other one that is already full.

 

Ford did that on their "works" Escort rally cars with 2 x 12v batteries.
One was 12v for the whole system, and the other was piggy-backed "in-series" to the firewall mounted starter relay/solenoid.

At the end of every stage they simply swapped the batteries around so the piggy-backed battery got charged [this is really easy when the life expectancy between services was about 60 miles, and they had unlimited resources]

They obviously had the same issues trying to crank over a high compression BDA engine with a Lucas starter motor

 

Somewhere, I pulled a switch box from. Peterbuilt that had a Detroit engine in it. My dad bought the truck as a glider kit.
Anyways the Detroit started on 24v and ran on 12v, I don’t recall taking the box apart to see what was in it, probably something like Kerry did

 

For what it's worth, I recall seeing an ad in a 1950s Hot Rod magazine for a 6 volt starter used for dropping a 265/283 in an early car, and it looked like a conglomeration of factory parts. I know that the first couple of years, the small blocks used a starter with the exposed linkage for the solenoid, like the early Buick/Cadillac/Oldsmobile V8s; maybe there's a combination of parts there that will work.

 

I saw the same thing a while back. I actually found a how-to guide on how to convert a SBC to a 6 volt car, but it sold before I could get my greasy fingers on it. I wish I had a picture of the cover at least...

 

Aren't points run at 6 volts, with a ballast resistor. regardless of voltage of the car?

 

closer to 8 or 9 v?

 

Points are only a switch, they don't care what the voltage or polarity is. The electronic versions are voltage & polarity sensitive.