1951 ford shoebox

[51 shoebox]

So bought me a 51 shoebox and having issues with wiring, and the starter, from my research I have found they are a positive negative starter, but when I put 6v to it I can't get it to spin. I can get it to crank only on 12v. I have two separate starters iv done this on and it's the same. Tried adding grounds, new wiring but it will only crank the motor a quarter turn at a time with a load on it. Any thoughts

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[wga]

If it is a stock 6 volt, then it likely has a positive ground. Do you have a 12 volt or 6 volt battery? If it was converted to 12 volt, then they are negative ground. Check your connections, should be very clean. From the relay to the starter the wire is about 3 feet long. Should be #1 or 0 gauge. Make sure the terminals are not loose on either end.
Battery has a full charge? If it works on 12 volts, if should work on 6volts. Do you
have a voltage meter? Wiring on these if straight forward. If you are testing a motor
on the bench it does not care what side is connected - negative or positive. It should spin - fast.

[51 shoebox]

Originally Posted by wga

If it is a stock 6 volt, then it likely has a positive ground. Do you have a 12 volt or 6 volt battery? If it was converted to 12 volt, then they are negative ground. Check your connections, should be very clean. From the relay to the starter the wire is about 3 feet long. Should be #1 or 0 gauge. Make sure the terminals are not loose on either end.
Battery has a full charge? If it works on 12 volts, if should work on 6volts. Do you
have a voltage meter? Wiring on these if straight forward. If you are testing a motor
on the bench it does not care what side is connected - negative or positive. It should spin - fast.

Can only get it to spin fast when I arc it off a 12v battery with jumper cables, my system is 6v, bought all brand new wiring harness from painless harness. Bought new 0 gauge grounds and positive wires, new 0 gauge from starter solenoid to starter, and have a brand new 6v battery.

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[Curt in AZ]

Any chance the system was converted to 12vdc before you purchased the car? Check the number of a tail or stop light to verify the voltage..

[51 shoebox]

Originally Posted by Curt in AZ

Any chance the system was converted to 12vdc before you purchased the car? Check the number of a tail or stop light to verify the voltage..

I'll do that, from my understanding through the tipical Craigslist seller, is he rebuilt the motor drove it about 600 miles took it to the shop for tune up and they put a new battery in it and put a 12v battery in it and fried the electrical, so since iv owned it if stripped it of all its stock wiring and started putting in a brand new fuse blocked harness. Alot of the old wiring was melted and and f*&ked up. Now it's got an aftermarket generator, pertronixs coil, stock rebuilt distributor, and the carb was all brand new when i went to rebuild it. If yet to find any resistors, but have found a few blocks with 15amp inline fuses throughout the dash and engine bay, are those resistors?

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[51 shoebox]

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Originally Posted by 51 shoebox

I'll do that, from my understanding through the tipical Craigslist seller, is he rebuilt the motor drove it about 600 miles took it to the shop for tune up and they put a new battery in it and put a 12v battery in it and fried the electrical, so since iv owned it if stripped it of all its stock wiring and started putting in a brand new fuse blocked harness. Alot of the old wiring was melted and and f*&ked up. Now it's got an aftermarket generator, pertronixs coil, stock rebuilt distributor, and the carb was all brand new when i went to rebuild it. If yet to find any resistors, but have found a few blocks with 15amp inline fuses throughout the dash and engine bay, are those resistors?

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But there is a resistor before the ignition coil

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[51 MERC-CT]

Originally Posted by 51 shoebox

I'll do that, from my understanding through the tipical Craigslist seller, is he rebuilt the motor drove it about 600 miles took it to the shop for tune up and they put a new battery in it and put a 12v battery in it and fried the electrical, so since iv owned it if stripped it of all its stock wiring and started putting in a brand new fuse blocked harness. Alot of the old wiring was melted and and f*&ked up. Now it's got an aftermarket generator, pertronixs coil, stock rebuilt distributor, and the carb was all brand new when i went to rebuild it. If yet to find any resistors, but have found a few blocks with 15amp inline fuses throughout the dash and engine bay, are those resistors?

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First, the starter doesn't care if it's negative or positive ground.
You say you are installing a 'Painless' wiring harness.
To my knowledge 'Painless' does not make a 6 volt suitable harness.
If that is the case then you are installing a harness that has the wrong wire gauges and may not be suitable for a 6 volt system.

[Frank Miller]

12 volts should not have fried the wiring harness as much as it should have fried all the components. A new battery does not necessary equal a charged battery. Also might be good to get the starter checked out.

[Marv]

Try replacing the starter solenoid.

[rotorwrench]

A 6-volt starter doesn't have the rpm or power of the same unit operated from 12-volt. Although they will operate on 12-volt, it's generally better if the field coils are changed over to 12-volt types when converting. They will last longer.

[JSeery]

I'm not sure I understand what you are attempting to do with the electrical system. If you are going to a modern wire harness, why not go with a 12v battery negative ground? If you are wanting to keep it 6v positive ground then you really need to go with an original style wiring harness. It is fairly easy to switch over to 12v if that is what you are wanting to do.

[flatford8]

Have you had the motor running?...... Mark

[51 shoebox]

Originally Posted by flatford8

Have you had the motor running?...... Mark

No I have not heard it run, but did pull all the plugs and put a wrench on the harmonic balancer and crank it around a few times to make sure it wasn't seized, then replaced all the plugs. What is located in the photo

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[51 shoebox]

Originally Posted by 51 MERC-CT

First, the starter doesn't care if it's negative or positive ground.
You say you are installing a 'Painless' wiring harness.
To my knowledge 'Painless' does not make a 6 volt suitable harness.
If that is the case then you are installing a harness that has the wrong wire gauges and may not be suitable for a 6 volt system.

Didn't mean the brand harness

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[Bob C]

"What is located in the photo"

Are you asking about the overdrive relay?

Bob

[51 shoebox]

Originally Posted by Bob C

"What is located in the photo"

Are you asking about the overdrive relay?

Bob

Is that what holds the inline fuse?

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[Bob C]

Yes

[51 shoebox]

Originally Posted by Bob C

Yes

Ok thankyou, now what would happen if the generator on there rn is 6v and I hooked a 12v battery up? would the regulator blow? Since it's rated for 6v, do I need to buy a 12v regulator

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[rotorwrench]

If you change to 12-volt Neg ground, you will need to change the charging system to 12-volt. The Generator can be swapped for an alternator or a person can mod to use a 1956 or somewhat later 12-volt generator with 12-volt regulator for those. It looks like the painless wire is more suited to 12-volt than 6. 6-Volt systems need larger gauge wiring and won't work well with smaller gauge.

I wouldn't suggest that you try any 12-volt components other than maybe the starter or overdrive activation solenoid on 12-volt (the big one on the transmission). Light bulbs will burn out and gauges will fry. Fifth Avenue Internet Garage has a nice little booklet that guides a person through a 12-volt conversion.

A starter that won't turn well with good large gauge cables and a hot 6-volt battery, is either not a 6-volt starter or it's got something wrong with it. Bad bearings, worn out brushes, fried armature, or fried field windings can all be a cause for poor performance or any combination there of for that matter. Loose or corroded cable terminals or corroded wire in the cable are bad news for 6-volt systems. Corrosion causes resistance and resistance equals less voltage through and poor performance.

[JSeery]

Lots of 6v to 12v information around. Here is one. http://www.how-to-build-hotrods.com/6v-to-12v.html