MTFCA Forum

I’m going to ask a question that I hope isn’t so totally stupid that I could barred from the forum for life…
Could a high compression head cause a starter to spin more slowly due to the increased compression and consequently work load the starter harder to spin the engine…. I am familiar with two cars…. One spins so fast I almost thought it was a 12 V conversion….the other is markedly slower…. To answer the usual and pertinent questions, the batteries are both new, all the contacts and ground….immaculately clean.

I have always been under the assumption, perhaps erroneously, that a stater either worked or it didn’t…

Sooooo? To replace the starter or not, that is the question.

Watch this video it shows the problem you might be having!
https://youtu.be/j2MpvCMLss0

In theory, for a motor to start and run, one needs fuel, compression, and ignition (spark). With a healthy motor, a quick motion of a starter handle will start a T motor.

With a starter the same will occur. It should not take high rpms of the starter.

A poorly performing starter is typically from a weak terminal stud connection. This soldered/riveted connection must be tight to allow the power to flow. Another issue is a gummed up armature. Possibly worn/short brushes.
Check the 3 areas/items in this order.
There are a few other potential issues that will require a rebuild. Insulator shorting, loose brush holders & a failed/sloppy front Babbitt bearing.
These will present with extra heat or smoking.

We need a few more questions answered before making a diagnosis.
1. Did the starter work before you put on the high compression head?
2. Do you know whether this starter has been converted to 12 volts? If it has, it won't work very well on 6 volts.
3. Did you do anything else to the engine except replace the head" If you have put in new rings or tightened the bearings etc, you might need to pull the car the first time you start it and break in the engine. After it is broken in, it should be easier to crank start or start with the starter.
4. have you done anything to the transmission such as work on the clutch or tighten the bands?
Anyway before ruling out an actual problem with the starter itself, we need to know more about these things.
Norm

You didnt address/confirm the battery cable sizes. 12V sized cables wont work well on a 6V system.
6V cables are at least twice the diameter.

Starters more often perform poorly (drag) than just stopping altogether.
Raising the compression will not cause problems with a good starting system.
A good starter with good cables, switch, grounds, and battery will have a substantial reserve power available.
They have to have reserve power in order to start the car in cold weather.
Raising the compression will actually make the engine easier to start, and most of the intermittent work of compressing the mixture is done by flywheel inertia.

I recently had this issue of a slow starter. Before I went out to have it rebuilt, I replaced all the connections, wiring, starter relay and rebuilt the floor switch for the starter. Now it turns just fine, without having actually done anything to the starter itself. Wiring does kind of go bad after a while (corrodes internally) and it had been probably around 30ish years since it had been done. The original wire gauge may have been a little too small as well. Might be worth a try before you take the starter out and tear it apart. Others here seem to think similarly.

Just for reference, my T is 6V with a high compression head.

Edwin & Eric .... I replaced all cables with 2/0 stranded cables, along with rebuilding the starter floor switch and added a battery cutoff switch since the battery thru the Runabout trunk is a bear to access in emergencies. The starter spins a lot faster with the same battery compared with " original" set-up. The small guage #2 ....12 volt battery cables are not the same. The standard 6 volt system works on a higher amperage, using the 2/0 cable is more than sufficient

Thanks for all the input…..food for the trouble shoot!

One easy test is to see what the voltage drop is whall cranking. That will indicate loss due to bad connections in the power supply between the starter & battery, including the switch. You still need heavy cables to carry the amperage.