My Bendix spring is deformed and scrapes against the "cup". I just bought a new bendix spring and it appears to be the same style and size as the old one. When placed on the Bendix the new spring is a little long and if the bolts are installed it will surely become deformed the same as the previous spring.
By the "cup" are you referring to the bendix cover that is held to the hogshead by 4 special thread screws? If yes then your trouble probably is NOT the bendix spring but the Bolts you are using to fasten it to the bendix mechanism. The heads of these bolts must be very thin or they will scrape on the inside of the bendix cover and knock it loose and oil leaking then commences big time. Measure the had thickness of each of the bolts and report back but the correct bolts have very thin heads and good temper too.
I meant "measure the HEAD thickness..."
Which spring are you showing us, now or old? That little difference in length should not hurt. How thick are the heads on the bolts? Some are too thick and can rub on the cover, may be whats happening anyway. I have seen more distorted springs that still worked.
Be sure to also use the correct locking lug washers, one lug goes between the spring coil end, the other is bent up over the bolt flat hex edge side when fastened firmly. That locks the bolts in place.
And below are some of the correct bolts, the ones in the background originals, the foreground has one with a head too thick, so take care in install with odd bolts. The bolt heads should be .140" thick (tall).
The reason that spring is stretched is from the engine "kicking". Kicking is caused by trying to start the engine with the spark advanced. The engine will start to run backward and put a strain on the spring. That strain will be in the direction to unwind the spring.
Also if the heads of the bolts scrape is is usually caused by the head being too high. See the picture in the above post by Dan. There were a few years ago some bolts being sold by the vendors which had too high heads.
Another possible cause of scraping would be a bent starter shaft.
Eric ; are you sure that you have a model T spring and not a model A.
This photo was done by Ron Patterson.
Shows why even most of the repop screws are still not quite right and need to be reground.
Norm: Wouldn't any flywheel rotation from a 'kickback' cause the bendix spring to wind tighter rather than unwind? I'm having trouble understanding how the bendix spring could become unwound, pls bear with me on this, thanks jb
Bendix springs can be distorted like Eric's under the following circumstances.
When the starter is engaged and the Bendix drive gear is in contact with the flywheel ring gear the high torque starting motor is pushing 12 foot pounds of torque and the spring tightens. The drive gear torque is multiplied by the drive gear to ring gear ratio of 12 to 1. That creates 144 foot pounds of flywheel torque to turn the engine.
If the spark lever is not fully retarded the engine can fire BTDC and try to force the engine backward with great force. This force tries to push the Bendix drive gear backward and will try to unwind the Bendix drive spring.
All this while the starter is still trying to create full torque. Hence damaged drive springs.
Eric's spring is not seriously damaged and probably could be reused, but it should be replaced.
Another important item mentioned above is using the correct Ford Bendix bolts and keepers. If the Bendix cover is pushed off the transmission cover while driving the damage can be disastrous if not detected early.
Make sure your initial timing is set per Ford recommendations and be sure the spark lever is all the way up when starting.
Ron the Coilman
You can chuck the repro screw in a lathe and face the head down to the proper width.
If you don't have a lathe, you can file it down.
Even with proper screws I've still found interference with the bendix cover if it wasn't centered up real well. With the spark plugs out and the rear end up on jack stands: Snug the bendix cover screws while the sealer is still soft, then reach up and hit the starter button. If there is ANY unusual noise, re center the cover and try again. (Adjusting in this manner you can also use the "incorrect repro" screws with good success if you are doing an "on the road repair", etc).
I just checked the starter shaft and there is some runout: 0.165" (0.42mm). Does that need to be addressed or can it be ignored?
Contact me and I will explain.
Eric: There is a 10-fold difference in the runout values given. If you measured 0.42 mm, about 0.0165" your starter shaft is in much better shape than if your measured value is really 0.165". respectfully,jb
Thank you James! I really painted an ugly picture of my starter motor shaft.
Yes, the runout is 0.0165".