MTFCA Forum

Hey all,

Last week I was called for a knock during the start up of an engine I rebuild two years ago.
Engine is running great with no noice and good perfomance.

Here is what I found:

The flywheel ring gear was replaced during the rebuild.
Together with the missing tooth, the starter gear is gone to.

Andre
Belgium

12 volt abuse? Too much spark advance on starting?

That ring gear is toast.
Were both the starter gear and ring gear new when you put them in?

ring gear and benbix were new.

Andre
Belgium

That’s the sort of damage that can occur if you use a 12v battery for starting. What voltage is it?

Other possibilities:

1) Spark isn’t properly retarded on startup.

2) Badly bent starter shaft.

3) Mesh between the two gears is incorrect. (Engine main bearings are line bored off center and/or the block or hogshead have a casting or machining defect of some sort.

4) The bendix may be occasionally locking up and isn’t properly disengaging from the flywheel on startup. The flywheel ring gear driving the starter bendix gear even just occasionally for a few seconds can cause rapid wear.

5) The person driving the car has stepped on the starter button when the engine is running. You can have major damage, usually much worse than that even if you only do it once.

It's early, but the proximity to that nut ...........

I bet that’s it! The balance ring on the bendix gear is hitting the nut and crashing / skipping the gears.

He did say he installed a new bendix. They have a solid machined one piece gear and balance ring. If it was an original bendix gear with a swedged balance ring, those nuts would have broken the balance ring off the first time the starter was energized…

I agree. Its them nuts. The bendix gear will engage to the flat face of the counterweight.
Look closely @ the nuts for damage marks.

Andre, if you ditch the magneto, retap the ring gear 1/4"-20, and use bolts and lockwashers all the way around the gear, short enough to be flush on the drive side.

big2bird wrote: ↑

Thu Oct 09, 2025 11:54 am

Andre, if you ditch the magneto, retap the ring gear 1/4"-20, and use bolts and lockwashers all the way around the gear, short enough to be flush on the drive side.

Not necessary to re-tap the ring gear.
If its a ring gear with the correct threads, there is a metric screw (6mm) that will self lock into the existing threads.

Thanks,

Didn't think about the nut.
The bolts are 6mm bolts. As said the lock up in the 1/4 20 tread in the ring gear.
I will use new shorter bolts and pin them as I do with the brass magnet bolts.

Andre
Belgium

I am not sure I would try 6mm in a 1/4-20 thread. Much too sloppy loose. Why not use 1/4-20 in a 1/4-20 hole??
Arent the repop ring gear threads 1/4-24? I don't have an experienced answer for a 1/4-24 thread.
6mm work well in the correct/original 14-24 ring gear holes.

I don't see any damage to the nut.

Andre, when you removed the magneto, did you install some paddles for oil?
I used 4) 90* apart. Short pieces of 1" angle about 3" long. Been a long time. Vendors have them if you want to see a picture.

oilers on the flywheel

Wow. Those are rather large.

There were similar slingers from a south manufacturer of T parts that fatigue & come apart.
Has that problem been cured, or will it be the reason for the next tear down?

With the Ford magnets in place, the number of magnets reduces the amount of pressure on each one of them as the assembly spins. Each magnet is in the "shadow" of the next one. With 3 or 4 steel vanes, each one gets a better "bite" on the oil, and probably has a lot more turbulence to deal with. I'd think that more, and smaller, vanes would be a better arrangement.