Can a Rocket III take down the establishment, and rule this island

[DesertRat]

Ok so got a few days off work and gonna try get this engine back together after sitting there in bits for a few months

Have to pull the head to replace the titanium retainers and also gonna change out the 8.2:1 pistons to the 8.0:1s.
One important job on the way is finding the missing tooth from the broken timing gear.

Can you spot it?

So after a bit of examination I think I know what broke the timing gear.
It was in the Stroker engine for several thousand trouble free miles and it didn't break.
So why did it break within 2000 miles when the Carpenter and TTS supercharger were fitted?
If the gear was just a dud then surely a random tooth would be the one to break.
But it was the tooth on the thinnest and therefore weakest point of the gear.
It just smacks of outward pressure like the crank expanded and cracked it.
Looking closely you can see a mark where the gear was pushed against the crank shoulder.

And if you look at the chamfer shape of the gear vs the radiused shape of the mating part of the crank.
Not shown here but the new gear won't go in quite fully to the shoulder because of this.

And couple this with the huge force the crank pulley mount puts inwards when you tighten up the big drive bolt.

I'm sure what happened was the gear didn't mate properly with the crank shoulder due to the different shape of chamfer vs radius, and the pulley mount had the gear pushed in on it hard (hence the mark).
The chamfered edge was being pushed hard against the radius, which acted like it was pushing outwards stretching the gear.
And there was no slight clearance there to allow for thermal expansion.
So while under this pressure the natural expansion of engine parts from the heat, well the crank expanded and cracked the gear.

So now I will sand the chambered edges of the new gear to make sure it mates nicely with the radiused shoulder.

Here's my .03 cents

More than likely this failure was a result of one of two or both of the following;

1) Tooling Shift or Tooling Wear during the Gear Production and/or;
2) Faulty Material to start with.

I wish I still had Chits owed to me around the Metallurgy World. A good NDT Tech could do an simple exam and tell you what caused the material to fail.

Here's a One-Dimensional WAG= I lean towards suspecting a tooling shift because of the fitment/non-fitment of two identical gears

A tooling shift is either tooling that wears during a production run and or an initial tooling set up flaw, (i.e. failure to zero your machine to the material at hand etc).

Small tooling shifts at multiple critical areas can lead up to a catastrophic issue, like what you've found.

This is why I prefer hand-fitted, Hand QC's Engine assemble methods.

Today's culture is lax at using and being proficient in the realm of "Attention to Detail."

Btw, Before I'd take any material off the Gear to fit to size, I'd determine the OEM spec's, sizing and dimensions, (including the Shaft OD and Shaft Chamfer).
There might be a bad batch of shafts and or gears still floating around. I'd then determine how much material is needed to be removed on a Mill.

Good job on the description and pics!

 

[DesertRat]

Turbo,

Sorry to hear about your Buddy.

We've all been there at 1 or multiple times in our lives.