Flathead turns very slowly??

JLford

JLford

Member
I have an 8BA flathead that had been sitting for a long time. I got the engine to turn with relative ease and i proceeded to get the usual parts: rebuilt carb, fuel pump, alternate fuel tank, new points and cap, etc. BUT!!

**the rebuilt starter motor (which had been exposed to 12 volts in the past) cannot turn the engine fast enough to start! it barely turns the engine over with the plugs in, and i can't for the life of me figure out why. Anyone know why??**
 
What condition is the battery in?? Good CLEAN ground point on the frame AND at starter conn AND battery terminals??
Paul in CT
 
Make sure all you cables are the right size, you said it was exposed to 12 volt. Did they change cables? If that did happen the 12 volt cables are too small. also check for good connections and grounds!
Tony
 
I did in fact switch the cables to the correct thicker ones, but the battery was in poor condition. I had another running 51 ford jumping it though, so the power was ample...so confused.
 
Sounds like you may have already isolated the problem - bad battery. If there's an internal short in the battery - buckled plates, sediment in the bottom, etc. - it would drag the whole system down. Like 1931 flamingo says, clean grounds and a good battery are a must. Good luck!
 
would a bad battery still drag the system down even if i was jumping it with another 6v car? thanks everyone!!
 
A good battery installed from another car should crank over faster than using jumper cables as there is extra resistance in the longer cables.Most jumper cables these days made for 12 V are rather small guage & will not carry the amps needed for a 6V system.Make sure that both mounting surfaces for starter are shiny clean.
 
JLford said:
would a bad battery still drag the system down even if i was jumping it with another 6v car? thanks everyone!!
Click to expand...

Don't think so. However, jumping connections are not nearly as good as actual battery connections. I would bypass the bad batt completely and see what happens.
 
maybe it is a 12V starter.....try jumping the starter directly with a strong battery and see what happens.....Mike
 
I had this same problem several weeks ago. Had a new battery and engine/starter still turned slowly. It was the ground. Took a electric drill and brush to the ground connection to the frame, cleaned it up, spun over great. The ground looked okay, but wasn't. Use some electric connection cleaner too!
This is one possibility.
 
I would begin by checking the battery cells with a battery hydrameter!

Do you have access to a DC amp clamp the amperage should not exceed twice the amp hr rating of your battery 200 amp hr would be max of 400 amps cranking and the battery voltage should not drop below 4.8 volts (at twice amp hour load) when cranking the engine over; in the above example if your starter pulls more than 400 Amps and the voltage stays above 4.8 volts I would suspect a starter! If the starter draws less than 400 amps and the battery voltage goes below 4.6 Volts I would suspect a battery or bad connections. In reality I would not expect the starter to pull more than 2/3s (270 amps) of the rated amp hr rating.

This opens another question how to check for voltage drops?
 
I had the same problem a few months ago.

Clean all ground points well. I took a drill and brush to the starter face and engine where they touch. Also all of the cable connections. Basically everywhere the motor touches the frame.

After all that, I still had the problem. I connected a 12v battery to the starter and it spun like a top. I was using a brand new 6v battery but when I took it to the store where I had bought it two weeks earlier, it tested bad. They swapped it out for me and everything worked great on the new battery.

Try a good 12v battery and see what happens(bypass the car's normal electrical path). I used jumper cables from my Tundra battery to the starter and that proved the starter was good. If the starter spins well with 12v then you either have a 12v starter or an electrical current problem.

Good Luck!
 
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