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Using 8 volt battery?


Frank Wilkie
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I'm considering using a 8 volt battery in my 1954 Chrysler 331 V8.   As I can remember my father use to do this and he had to adjust the voltage regulator.. My question is, what terminal do you adjust on the regulator and how do you determine the setting is proper ?     The instrument panel on the car only has a warning light.

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Why do you think you need an 8-volt battery? They're usually band-aids, not solutions. Chrysler built cars that started reliably under all conditions in 1954, no reason the same can't be true today. An 8-volt battery will merely mask the real problem you're having, which is probably a combination of undersized battery cables, bad grounds, worn starter bushings, amateur wiring "fixes" in the past, incorrect timing, and maybe a tired battery.

 

If, however, you've already decided to do the 8V swap, your shop manual will tell you how to adjust the voltage output of your regulator. You'll have to push it past factory specs so their gap recommendations will be meaningless and some experimentation and measuring output will be required. You can use a voltmeter across the terminals of your battery to see how much voltage the generator is putting out--just be sure you're testing it above idle since generators don't put out much juice until 25-30 MPH (output goes down as generators heat up, so you may have to do it again in the summer after a hot day of driving to be sure it's keeping up during driving season). Remember that to charge an 8-volt battery, you'll have to push your system to 8.6 - 8.9 V or so at max output. Ohm's Law also suggests that the amperage output of your generator will probably go down as voltage goes up, so you may have less total electricity available to run headlights and heaters and radios during normal operation. The only real difference is that the starter may spin marginally faster on 8V, but I bet it's not a huge difference.

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It is the same adjustment as you would use to adjust the voltage for a 6 volt battery. With an 8 volt battery you have 4 cells instead of 3, so take whatever voltage the service manual says and divide by 3, then multiply by 4. For instance if the voltage should be 7.5,  7.5 / 3 x 4 = 10v. Voltage regulators are temperature compensated, so the manual will probably tell you how to figure the normal charging voltage at your temperature (for 6v, then do the 8v math).

 

There are usually 3 relays in a voltage regulator. Voltage regulator, current regulator, and cutout. You have to find which one is the voltage regulator (check the manual). On most cars you bend the little hook that holds the return spring. Some have a screw. You have to put the cover back on to recheck the voltage, so plan on taking it off and on a lot. Two tenths of a volt is a change on a voltage regulator. 5 tenths is HUGE change. You need an accurate meter. Try it with a digital if you have one and it might work, If it wont, then you have to find an old generator test set that will show you tenths. Every time you change it, put the regulator cover back on, rev the engine up and give it time to stabilize. Voltage is checked at the battery. Make sure the battery is completely charged before you start, or it can fool you into making a wrong setting.

 

That said, I agree with Matt Harwood. Don't do it. I have never seen this kludge fix anything for very long, and you will go through a bunch of bulbs. An oversize 6v battery (and big heavy 6v cables)would do more good than 8v for a particularly stubborn vehicle, but even that shouldn't be necessary. I recommend chasing down the original problem rather than trying to do band aids.

 

P.S. I remember when I was a kid my dad did one of those 8v conversions on a slow cranking International truck we had. It actually started on the button for 2 weeks. We had it for 30 years. Good thing our house was on a hill.

 

 

Edited by Bloo (see edit history)
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Count me on the never use an 8 volt battery also.

 

Fix the car, it started in all sorts of weather when it was new with the original 6 volt system. 

 

To keep an 8 volt lead acid battery charged, the voltage regulator will need to set up to 9 .2 to maybe 10 volts, like Bloo says. This will stress the generator. And the extra voltage will stress ALL the light bulbs.

 

What are you trying to fix?

 

 

2 hours ago, Matt Harwood said:

Remember that to charge an 8-volt battery, you'll have to push your system to 8.6 - 8.9 V or so at max output.

 

Nope, that will just keep the 8 volt battery sulfated.  I see it with people using 8 volt batteries, they keep failing after a year or so. If  a 12 volt battery typical charge is 13.8 volts, then and 8 volt battery needs 9.2 volts minimum to get good life out of them. Much easier just to keep the 6 volt battery properly charged by fixing the stock parts.

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I fell in the 8 volt trap back in the 1960's, because I didn't know any better.  My first car, '31 Chevrolet, had an engine rebuild that was so tight it wouldn't turn over.  We used an 8 volt, but as mentioned it causes all sorts of other problems.

 

6 volts works fine, always has and always will, but now you're dealing with people who put small 12 volt cables in system, and all the corrosion between riveted frame joints, so grounding is a big problem.

 

Use correct size battery, use heavy cables made specifically for 6 volts, and run a separate ground directly from battery to starter.  Your problems will disappear is the starting system is set up correctly.

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10 hours ago, Frank Wilkie said:

Ok,,  I'll just stay where it's at.. 6V....   it isn't all that bad.. Just like a quick start..

 

To insure a quick start, make timing and carburation  right on spec., Good spark and compression. Should be able to start in a couple of revolutions.

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Personal experience....  When I was young (18 yrs old) and had just bought my 1953 New Yorker,  It turned over rather slowly, as if it wasn't going to "get there".

My father said I should put an 8V battery in it and it should be fine. 

Conversation went something like this..  Dad, "Those damn 6V systems were lousy, even back then, That is why they all went to 12V"

 Me, " But it is a 6V system"

 Dad, "It won't hurt anything, and your starter will turn it over like it is supposed to"

 

 I doubted Chrysler meant for an 8V battery to be in there... What about the lights and gauges, I wondered to myself.   So, I asked my Grandfather's Brother, who was a Texaco service station owner after the war... He said, "Get your starter rebuilt"  and gave me the name and number  of an old fellow to take it to.

 

 I re-installed the starter after I got the call to come pick it up, and DANG, if it didn't turn over like the day the car was new!

 

 That was 35 years ago.  The starter still turns the engine over with "gusto" !  BTW.. I still have the "modified" 5/8ths open end wrench rattling around in my tool box, just in case I ever have to get that almost hidden nut off and pull the starter.

 

 My advice:  Find an old fellow who rebuilds starters and generators, and have a set of brushes installed and have it checked over.  Keep with 6V!

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Pretty much, my cad's v8 (I think it's 312 cu from memory) starts almost instantly with 6v - about the only time it doesn't start is if you hesitate and take your foot off the starter prematurely. It's got a good battery, rebuilt starter and rewired.

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My 53 Lincoln is comparable in design to your Chrysler. Your engine is a 331 cu.in. with a 7.5:1 compression ratio and my Lincoln has a 317 cu.in. engine with a 8.0:1 compression ratio. The engine turns over just as fast as my modern car and it has 1 optima battery.

 

Slow cranking can be caused by an undersized battery, weak battery, bad cables, tight engine or a bad starter.

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On my '31 Pierce, running a ground from battery directly to starter made a big difference, turns over at least 50% faster than without ground.

 

The comment on starter rebuild is accurate, just "good enough" doesn't work with a starter.....I'm lucky enough to have a great starter/generator guy close by, and for about 100 bucks he makes it like new....

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1 hour ago, WPVT said:

I've got big cables, a big 6 volt battery, and a slow turning starter. The ground cable connections are all clean. Has a direct ground cable to the starter make a big difference for some ?

 

I was the same as you. When I switched to bigger cables for my straight 8 I also ran another cable from the frame to the starter. I wouldn't believe it if I didn't hear it for myself. Cranks awesome. No regrets. 

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Interesting...So you ran a cable from the starter to ground. I was envisioning a cable from the grounded side of the battery to the starter.

I'll probably start by refreshing the connection from my battery ground cable to the frame. Then I'll do a visual check of how the engine block grounds to the frame. 

I always like to start by fixing what's there. Part of the allure of antique trucks for me is that the engineering was pretty good. Strong, durable, and smart.

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Follow the current flow.

 

Some cars run the battery negative cable to the frame (and or body), and then another one from the frame (and or body) to the starter (or engine or transmission). In this scenario all cables (positive too!) must be equally big and good.

 

Some cars run the negative cable directly to the starter (or engine or transmission). In this scenario, the positive and negative must be big good cables because they carry starter current. The cable back to the frame (and or body) must exist, and be really good because almost all other electrical equipment uses it, but because the starter current does not go through it, it does not need to be as big. It can be as big as the others if you want and it wont hurt anything.

 

 

Edited by Bloo (see edit history)
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The original setup has the positive ground cable (4/0 AWG) running from the battery to the truck frame where it is attached with two tinned terminals. The steel frame point of contact looks tinned as well. The question is how well the starter (and engine) is connected to the frame. Certainly well enough to turn the starter, but maybe not as well as it could. I'm not sure just what the motor mount looks like or whether there is another strap connecting the engine to the frame electrically. I'm going to put a 0/4 AWG ground jumper from the battery to a starter mounting bolt, just to see if the connection can be improved. 

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On my negative ground car I ran the positive cable to a starter mounting bolt, this greatly improved starting but made my lights dimmer.  I then ran a new ground from the engine to the frame.  Lights then were as bright as before.  Eventually I replace the 3 brush generator with an alternator because my night time driving exceeded the power output of said generator.  All problems solved.  By the way all my wiring is original except for the wires added for turn signals.

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You can use a volt meter to check the grounding connections for the starter. That way you will be sure and not waste a lot of time and money replacing parts. Make sure that you connect your meter directly to the post, not the connector. The connector may have hidden corrosion and you would miss it during the tests.

 

Connect the + meter lead to the POS battery post and the COM meter lead to the starter case and turn the meter  scale to the  5 volt scale. Crank the engine with the ignition off or the coil high tension lead disconnected and read the meter. The reading should be 0.1 Volts or less. If it is higher you can move the COM lead to the engine ground connection and repeat the test.

 

You can also use the volt meter to check that the starter motor is getting enough voltage  by connecting the + lead to the starter terminal and the COM lead to the NEG battery post and cranking the engine with the starter. The reading should be 0.3 volts.

 

Another test is to measure the battery voltage while cranking the engine. Connect your meter to the battery posts and crank the engine while reading the meter. The battery voltage should stay above 5.0 volts

 

If your starter circuit passes these tests, it is time to have the starter checked out and rebuilt if necessary.

 

Edited by 19tom40 (see edit history)
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My experience is the vast majority of 6v conversions are do to slow cranking. I always ask the customer to trust me that I can fix the issue without converting to 12v or simply installing an 8v battery. Both of which can come with negative side effects. Things that I have found are wrong size cables as has been said earlier. Usually store bought premade 2ga cables in the bubble pack. 6v needs 2/0 or larger. The other issue with these cables are they usually use steel ring terminals and not copper. I tell people to take a magnet when cable shopping if either the clamp or ring stick to the magnet don't buy it.  You should do the same if you have cables custom made. Grounds are always lacking on classic cars even from the factory. Electricity is a learning process even for the engineers. Look at modern cars and all of the grounds they use. So adding small battery to body or main battery to frame or block is always good. In some cases cable location as has been mentioned has improved or solved issues. We recently had a 61 Corvette with slow crank when hot. We moved the ground from the frame to the starter mounting bolt and the issue was solved. Within the starter some issues are worn bushings and thrust washers. Causing the armature to not run true. Also within the starter on fresh rebuilds can be brushes that have the wrong copper to carbon ratio. 12v brushes use more copper then carbon. 6v usually are the other way. And 12v brushes in most cases are similar in size and mount and to save money a rebuilder that does not see many 6v starters will use what they have rather then invest for 1 sale the right part. Brushes that have copper wire leads like Ford and Autolite used if the lead on the brush is undersized it can cause issues. Ford used the same brush in both 6v and 12v but the ones 6v ones used the larger lead. The ones made today use the smaller gauge size. The last cause I have found is that the regulator has not been properly set and is undercharging the battery. 6v needs to charge at least 7.0v if not slightly higher based on your driving. Meaning slow speed, short trips need higher. Longer trip higher speed lower end.

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Well, I bypassed the battery to chassis ground with a 4/0 cable direct to the starter and it made a big difference. The existing ground cable was clean and secure, but in the final analysis it probably depended on a aged motor mount for the chassis to engine electrical connection.

So for 6 volt systems, 4/0 is the way to go.

By the way, I got my cable made up by a guy online, batterycablesusa.com. Nice fellow, quick, inexpensive and knowledgeable. The 4/0 cable has more and finer copper strands than the original, so it's heavy but very flexible. 

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Wpvt,

Most welding supply houses carry 4 ought and heavier copper cables by the roll.

Mine in Denver gave me several odd length bits, and I bought the end fittings from them too.

For both the Buick and the Chrysler 6 volt systems, I made a couple of engine / starter to frame jumpers and it literally "woke up" the starter.

Head lights too.

 

Mike in Colorado

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If it still has the braided ground cable get rid of it or get a new one,my 50 Windsor had the original braided ground cable and gave me fits until I replaced it then it started quick as a 12 volts. I would not start when damp but after I changed the cables it would fire right up even after raining all week and it had to sit outside.

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One thing that you might also do is if the connectors are crimped to the wire cable, you can solder the cable to the connector. 

 

As we said in the wiring business,  solder fixed lots of ills not limited to less than tight crimps, corrosion, etc... 

 

I have gotten to soldering almost all connections when it comes to the starting system.  Just belt & suspenders that works well.

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When I got my '32 Chevy the engine turned over a little on the slow side but better than any Model T I ever had.

EVERYTHING on a Model is anemic........ :wacko:

Anyway I didn't like the crimp on the starter end of the hot cable so I took it off and cleaned it as best I could and soldered the connector.

After that the starter spins the engine as if the spark plugs were out....... 👍

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