The Stovebolt Site Forums The Shop Area The Electrical Bay Starter amperage

I am sure this has been asked before, but how much amperage is required to spin starter on a six volt 216.

That's a very difficult question to answer. It depends on the tightness of the engine, compression, the internal resistance of the starter, and several other factors. I've seen current draw in excess of 300 amps at times when doing a diagnosis of a 6 volt starting system. Very few ammeters exist that can measure current that high, but there's a work-around. Use a voltmeter to measure the battery terminal voltage during cranking, and then use a carbon pile battery load tester to pull the battery down to the same voltage and check to see what amperage that requires. If a starter ever bogs down where it can't spin up to full speed for whatever reason (usually low battery voltage) the amperage draw skyrockets and can do major damage to a starter in just a few seconds. Never, ever keep grinding on a starter as the cranking speed slows down- - - - -stop beating that dead horse and find out why the cranking speed is dropping.
Jerry

What you say makes perfect sense, and add in the cold to an engine that has sat for a couple months. This could be either the engine or the starter very easily, or both. I tried to start it the other day and used two batteries, one the regular installed and a second as a jump source. Both had a charge. I will take the starter out and see how it spins with no load. I have at least one other starter for a back up on another engine and will test that too. If both spin well, I will have to surrender and go into the engine again.

You never say you have a problem or what the problem is. I don't know if this is a 6V or a convert to 12V.

It's a lot less work to get a "no load" test by removing the spark plugs. Bench-running a starter with no load whatsoever determines exactly nothing. A no compression spin will tell you more about the condition of the starter, because it's going to still be spinning the engine, just not fighting compression in the process. You should be able to turn the engine sans plugs pretty easily by pulling on the fan blades unless the cylinder walls are rusty, etc.
Jerry

Like I said before, it is a 6V 216 that has been sitting in a barn for several months, the last of which have been well below zero. I am deciding whether to get another 216 going to put into this truck just to get it back on the road or fix this expensive rebuild that has gone south. I will pull the plugs and see what happens.

A quick method of waking up an engine like that would be to disable the ignition by disconnecting a coil primary wire and spinning the engine with 12 volts after putting a little oil into the cylinders. 12V won't hurt the 6V starter at all if you limit the run time to 10-15 seconds at a time. Once it's spinning freely, then be sure you've got a good fuel supply and hot spark and go for a try at a run.
Jerry

Sorry, missed the 6V post.
It always seems to me that a 216 ends up costing more time and money than it's worth. It always seems like a full pressure 235, or up, is a way better choice.

I don't understand why 216's are more trouble, but they have a stigma about them.. The rebuild is not much different than a 235. All the machine work and assembly is the same as far as I know. The Babbitt bearings are fit the same as inserts using plastic gauge and the mains are already inserts, the oil line to the head is an interesting wrinkle, but even that is not that a big deal. In my situation, it was either me or the machine shop that got something wrong causing things to be too tight during assembly. Once running, the 216 is a strong engine that will run forever. This one I am talking about has run for up to an hour with decent oil pressure and stable cooling. I have not been able to get a decent compression test done because it has not been on the road and run under load. I have done two others and a 235 with no major issues, and all turned out to be very good strong engines.

Worn out 216's get a bad rap due to low oil pressure and excessive rod bearing clearances. The rods don't affect oil pressure because they're externally lubed by the spray tubes, but loose rods do get noisy. The modifications I'm planning for the next one I build - - - -insert rod bearings, aluminum pistons, higher-volume oil pump, and a lip type rear oil seal, should make a good engine much better. I'll also be doing the break-in run on a dyno, so no road miles will be needed for ring seating.
Jerry

You aren't going to believe this, just drove out to where this is stored, put some gas in the carb, stomped the starter got the slow roll and it fired. Ran badly for a bit and flooded out. Battery was low and I am charging it now. This engine has a 6 V alternator if that makes any difference. I am sure there is more to this story than what I have found so far. Has been driving me nuts for years now. Suppose this thread should get bumped to the engine section??

So would you make this a full pressure system or still use the spray tubes?

There's nothing wrong with a spray oiler- - - -some oldtime round track racers believed the non-drilled crankshaft was actually stronger than a full pressure crank. Just be sure the spray tubes are aimed correctly. The oil pump modifications I'm going to be doing will give about 20% more oil volume, which should cure the low oil pressure complaints on a hot engine, and also make the spray tubes squirt harder. I'm using Perkins Diesel engine rod bearings, which also allow a "worn out" 30 under crankshaft to be reground another 30 and use a standard diameter Perkins bearing insert. That also slows the peripheral speed of the bearing, something NASCAR engine builders do routinely when they use tool steel rods with Honda rod bearings. If a 9K RPM superspeedway engine benefits from a smaller rod bearing, why wouldn't the same mod help a stovebolt? Aluminum 235 pistons are a drop-in fit for a 216 with a 60 overbore, resulting in 224 cubic inches. That also gets rid of the bearing-pounding cast iron pistons.

I believe a 216 set up that way will give most 235's a run for their money, performance and reliability-wise.
Jerry

What's your timeline on getting one of these put together and running? I keep seeing your posts about this recipe for an upgraded 216, and I'm intrigued. I'd like to know how it works out.

My "part-time" job keeps getting in the way of spending much time in the shop! It seems that "retired" ASE certified master mechanics are in short supply, and the folks down in Florida who schedule the warranty claim investigations I do are keeping me on the road in nine southeastern states around 1,000 miles a week or more! In addition to tinkering with stovebolt engines, I'm also about six commissions backlogged on the custom deer rifles I build! I'm hoping to get a demo engine built up sometime this summer, and putting it, and my engine dyno into operation on a trailer. Then I can show up at a few events like the reunion in KC or Homecoming, and back up my fertilizer flinging with some facts and figures!

There's nothing particularly new or innovative about these ideas, and it won't hurt my feelings at all if somebody with the time and shop equipment available to build one beats me to it. Putting 235 oil pump gears into a 216 housing involves making a spacer to go between the housing and the base plate, but that's child's play for any competent machinist. Ditto for machining the back of the block for a lip seal, although my idea of using a cylinder boring bar to do it seems to be an idea nobody else has come up with.
Jerry

I have just the truck to road test thing in.

I went out to the truck the other day and tried to start it and it fired with a single low battery. I also have a 6V alternator on it as well. It didn't run buy a few seconds, the carb flooded out again. Seems that the last fix didn't last that long. The temperature is now staying up a little so I am sure that has something to do with it.

sorry i'm late to this thread,
the 6V starter motor should max out at about 525 amps, that's the locked test specification, see attached excerpt.

any rotating current will be less than locked (universal for all rotating machines)
once rotating there is back EMF, locked scenario has no back EMF to oppose current.

the no-load test should be 65 amps for 47-53 6V starters

to test i recommend:
clamp the starter body in a large vise,
attached amp-meter in series with the positive post of the batter and the starter,
ensure the amp-meter polarity is correct for anticipated current flow
touch negative of the battery to vise by hand
do not run it for more than about 10-15 seconds no load, it's bad for the commutator
once the RPMs have settled down and running smooth, note the amp reading then stop the test

i would use a clamp DC meter for this application
set it to the 1000 DC amp range
-s

Thanks, this helps a lot!

Depending on how the starter is wound, it will either reach a set maximum speed, or the RPM will increase without limit. Running a series-wound starter motor for more than about 5 seconds is inviting disaster- - - -as the speed increases, it can throw the conductors out of the slots in the armature. A shunt-wound motor will hit a moderately fast, but safe top speed and level out.

As a matter of precaution, I will not run a starter "no load" for more than a couple of seconds. I'll crank an engine with the spark plugs removed for considerably longer, but more than 15 seconds that way makes me uncomfortable.
Jerry

I am going to start this by checking things out with the plugs out and see how fast it spins. Then I will pull it out and bench test it against the 65 Amp standard.

all self commutated brush type DC motors have a maximum no load speed regardless of winding type
the back EMF is directly proportional to RPM, so eventually the two will reach a balance after losses and the motor will settle to a steady state RPM.

i will try to explain,
when the brushes swipe over to the next bar on the commutator a small portion of the rotor winding must change current flow direction
this change in current flow must increase in frequency directly with RPM
the impedance (resistance) of an inductor increases linearly with frequency Z=jwL, or Z=2*Pi*F*L
so as RPM goes up, the inductance of the rotor looks like an increasing impedance
this is why the starter current drops with increasing RPM, which means the total power drops with increasing RPM

at steady state your starter spinning in the vise will only be consuming on the order of 400-500 watts, that's 4-5 100W light bulbs worth of heat
so how long can a big block of iron like a starter absorb about 400-500 watts before getting too hot?
that's how long you can run that starter non-stop without appreciable damage
but it will be wearing out the brushes like mad
but wearing them out at a constant RPM, not an increasing RPM


there is one type of motor than can increase RPM unbound under no load, but it is never operated in that way
an induction motor with a separately excited rotor capable of synchronous and non-synchronous operation will present the line with a negative impedance if the rotor is left OPEN,
in this situation the induced voltage on the rotor winding will increase in voltage unbound until the line load presented causes circuit breakers to open up.
if the circuit breakers do not open up in time the motor will experience arcing across the slip rings or through the winding insulation in the rotor because that rotor voltage will be going up up up!

usually the rotors do not throw their windings in these cases, the machines have only a few 10 thousands of an inch clearance between the rotors and stators, this gap is made as small as possible to increase efficiency, due to vibrations and machining tolerance limits the rotor will begin to crash into the stator and become quite "turbulent" this crashing and friction will produce an amazing display of sound, molten bits of metal and sparks until the whole assembly finds a way to come to a flaming stop
-s