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Discussion Starter #1 (Edited)
I have BBC 11.5 comp. Motor has always been hard to turn over even by hand but runs great and has some miles on it.

Factory 427 Vette cast iron nose starter.

Did voltage drop and within .2 through out. Rear mounted bat with 1 welding cable. Starter pulled off block put still wired will have from a 13.2 battery fresh off trickle that will go down to say 12.8 volts at the battery lug on the starter when spinning. Starter has 3rd lug for points that is being used to trigger ignition. That reads at 11.8volts as above spinning starter.

Now take the exact set up with zero done to it and install starter and goes bad. Now voltage at crank goes down to approx 11.3-11.8 volts. Then trigger lug for points goes down to 6.8-9 volts. Wire is not hooked up to coil and no resister.

Starter tests at 150 amps draw out of car. Solenoid is approx 15 amps draw to activate.

Battery is new iNTERSTATE that has been tested by several big outlet stores.


Problem is the low voltage doesn't effect starter spinning as it spins as if no issue at all. No grinding no nothing. The low trigger voltage causes issues.


Could the starter just not be enough to handle load? Too many amps draw causing low voltage? I hate to give up on it as I do not like the offshore mini starters too much. I have zero alignment issues and GM used them to start some fairly big compression engines??


Ideas???
 

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That can’t be unless there is voltage drop through the solenoid. The terminal to the coil resistor by-pass should have the same voltage as the battery cable terminal if it is not connected to anything.

Measure the voltage drop across the solenoid from the battery cable terminal in to the terminal out to the copper straps going into the housing. If the starter has load on it, I don’t think there should be much drop, maybe .1V, I don’t recall measuring it before.

Look to see if the round wire snap ring is snapped inside the metal ring where the drive gear comes to the end frame when the solenoid moves it to engage the flywheel. I recall having trouble with the gear not being able to move far enough to allow the contact in the solenoid to seat with sufficient force.

Do you know the trick of turning over the copper contact input terminal so the unworn area is on the contact side? Take the plastic end with the terminals off the solenoid and you will see what that is about. Turn the stud for the battery cable 180°.
 

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Discussion Starter #3
When the screw is removed from the ground strap and voltage checked at pos cable with amp clamp it only draws 17 amps (solenoid isloated)

The only time the voltage drops is when the starter is loaded with the pressure of turning the engine.

It test 150 amps when done off car. My clamp does not go over 200amps so that is where it gets lost with cranking under pressure of turning engine. That is why I am questioning the severe voltage drop.

Starter is fairly new and I took it apart and everything looks good.

Solenoid is brand new from NAPA and I even checked it. I can't get more then 11.5 out of the ignition side of the starter even with the battery hooked directly to starter with over 13 volts while on charger so I will assume that is just internal resistance as it is brand new inside with not even a mark on the lugs or disc. Didn't the discs used to be brass inside also? Now they look like a plain washer.

I would guess it is starter at this point but I just do not want to give up on OEM style starter.
 

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That starter is FUBAR. Take your test rig to the store and test another like it. It has been several years since I did a free running test like you are doing but we always tested starters on the floor with a battery and jumper cables and I think it would only be about 25-30 Amps on a free running starter. Low compression engines crank with as little as 150 amps.
 

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Me thinks you have a bad armature. Or possibly have a LT factory starter instead of a HT factory starter. If you want, I can make you a ST factory style starter that will start a siezed motor. Do you have a picture of your starter, especially around where the solenoid is from the side. Also if you want to pop the back housing off and take a pic of the comm bars on the armature, I suspect they will be minor pitting, arcing on them.
 

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Discussion Starter #6
I am fairly sure it is the starter at this point. When I popped the rear cap it is full of gold colored dust.

Can you elaborate on HT? ST? LT? It is the higher HP with the extended sized case that takes the spacer bewteen the solenoid and ground strap.

I went so far as to re rig wiring to front mount with same cables and I did gain .5 volt on cranking then again battery has been on tender and hard to get exact 12.8 battery volts.

Ray shoot me a PM with pricing. Either that or I am going to get another DB offshore deal and keep rear ground as is and make up difference at lower amp draw starter.

I love fiddling and testing but it is time to get it done.

So many threads on starters surprised no real hard info on which starters draw what?

Thanks
 

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LT (aluminum fields) lowest torque starter produced by GM. They thought it was a great idea, until they figured out if the starters went above the 49th parrallel they didnt make enough power in cold winters

LT (copper fields) higher torque than previous, found on a lot of 6cyl cars and forklifts. Actually has the ability to spin faster than other starters.

HT highest torque starter produced by the factory, typically found on 8cyl cars. This starter had heat soak issues and performed remarkably better when main battery cable was upgraded from 4ga to 1ga.

ST an after market creation, most powerful starter available for GM. Problem is it requires over 500amps of power and is in the same size case as previous mentioned units. Was our goto unit for racing for 25 years, and have yet to see anything they wont crank over, including what most would consider to be siezed, 427.

Though untest it is general accepted that after pullin, the above starts draw approimately 1amp per cubic inch at 9 to 1 compression. The ST likely 1.5amps x.

GM PMGR (Mini starter), is as strong as HT starter, but requires about 1/2 the amperage, and is considerably smaller, so fitting headers is easier.
 
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