Chewed up flywheel

Ditto.

V8 engine has four compression "strokes" per revolution with points of least force are half way between each of these. If you have ever rolled an engine over by hand you will know how hard it is to take each piston over top dead center of it's compression stroke. If the engine stops near the peaks of any of these compression cycles it is going to continue to roll over or roll back to one of the lower force points of rotation between the TDC angles. All things being equal the odds of stopping at one particular point in rotation would be only 2 in 8 and you would expect to see wear zones every 90 degrees, but things are never equal. A new engine I would expect to be more random with a bias toward stopping just before it's strongest cylinder, but an older one will definitly get set in it's ways.

Mike, I hope you're feeling well. Question: Is it possible to flip the ring gear around to the good side and still use the same ring gear? Also, is flipping/replacing the ring gear better suited for a machine shop, or can I do this myself...and how?

Thanks Mike.

Ug, hanging in there thanks, now have the laptop up on a music reading stand so I can see it to type at least.

I believe the teeth are tapered so the gear only goes on one way, could be wrong there but... I had a defective new starter eat my ring gear and couldn't flip mine, had to replace it.

Ring gears are inexpensive at least, it is just a labour intensive job.

The shop baked my gear in an oven and then torched it and froze my flywheel and it just slipped together.

They had to cut the old one to get it off also.

Mike

2000 Cherokee Sport 86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00 'New' frame and everything else in '09. Some Canadian Bush Trip and Build Photos:

Technically, the randomness would be 1 in 4, which is pretty near the same as 2 in 8.

But still, killing the spark instantly gives the engine no reason to spin, and all other things being equal, it should stop instantly. If it dies not stop instantly, there is a malfunction of one sort or another.

There is no mechanical reason for your assertion of a predictable stopping location of the flywheel.

The gear on the flywheel probably can't be replaced, that is, the flywheel has to be replaced in order to replace the gear.

There are a few cases where the gear can be removed from the flywheel, but as a practical matter, the gear and the flywheel are the same thing.

If the gear is a separate part, it cannot be reversed.

The gear teeth are cut to be rounded on the side facing the starter, and the side facing the block is cut at 90 degrees. I'm not sure if the teeth are angled (helical) or not, but my weak memory is not. But one edge is rounded and the other is not.

Flywheels don't stop instantly. It's the nature of the beasts.

It's called inertia, Jeff. Once you cut off the spark the motor will wind down, not stop instantly...unless of course you're running 14 to 1 compression or something like that.

Even then. I used to have a boat with a Volvo diesel that could be hand started. To start it you flipped off the compression lever, which held the intake (IIRC) valve open, spun it up with the crank, then hit the compression and the inertia of the flywheel took it through a compression stroke. After it fired once it was running.

They stop instantly enough that there is no reasonable predictability of where they would stop. The topic is an assertioin that the flywheel will stop so that the starter can regularly hit the same 4-inch section of gears. I say that the starter might roll over the gears, but not make its initial contact on the same section of gear.

Hi Jeff, I've had it happen to an old chevy, I and other people here have told you it happens and why. If you care to spend some time with google, or some time talking with the grey haired mechanics, they will tell you it happens that way. Some time you should like pull the coil wire on a running engine and estimate how many revs it takes to stop, also note the occasional reverse rotation when stopping. Mark the timing pully and do some tests. BTW, earlier I said 2 in 8 deliberatly since there is two revs for a complete engine cycle.

The flywheel will attempt to keep the crank spinning, but the crank weighs a lot more than the flywheel, plus the crank has to try to push those pistons up and down against the air column in the cylinder. The flywheel tends to lose this argument quickly. Dont even recall seeing dyno engines tending to stop at any set point as an individual piston tries to move upward against a closed valve.

It is Murphy that dictates that once you have a marginal starter bendix, it will continue to chew at one single spot in the flywheel until it removes that tooth, then move on.

Had a mopar 318 with a chewed spot on the flywheel, it would start just about every time unless on very rare occasion it actually stopped where the [replaced by that time] bendix just happened to hit the chewed spot. Luckily was a stick so you could just bump it a good one and drive away. Ran that way for several months until could get around to replacing the flywheel. Didnt even hurt the new starter, although I wouldnt recommend a lot of experimentation.

Not really. The weight of the crank has nothing to do with it. It will act more like the fly wheel, spinning a weight around it's center. It's on bearing. If anything, it will help it maintain it's spin. Now, the pistons and valve drives do have something to do with what you are saying.

Yep, the crank is balanced so it's just the piston compression strokes.

Either way I've noticed (especially with the chevy 305) that the harmonic balancer usually stopped in one location (conveniently grove down so I could chalk it for timing) Cyl 4 and 8 had low compression.

a predictable

Heh, I know that the 302 Ford I was trying to locate #1 TDC on Friday kept stopping in one spot...just *past* TDC, of course. I've been doing this a lot of years and I've changed more than a couple of flywheels that were chewed up in one spot and totally fine everywhere else. It happens. Not a government conspiracy, not Obama's fault...it just happens.