Cracked Crank Nose Sprocket

[DarkPira7e]

So, finally tearing apart my previous engine to see what actually happened.
Preceeding failure, I had some cam codes (hell if I can remember what they were)

Was driving the car for about 30 seconds after it had been warming up for 5 or so minutes. Car bucked hard, sounded like crap, and I coasted back home after pulling a u turn in the middle of the road and parked it.

That was early 2020 I think? Anyway, finally tearing into it.

Looks like the crank sprocket fractured, has anyone else seen this?
4 broken rockers have been found in the heads so far as well, but likely were caused by the timing changing suddenly (I expect, I don't have evidence to prove this)

Anyway, just curious if anyone has an idea. The timing cover had definitely been resealed by someone who owned the engine before me.
For anyone who does not know my car's story, read my build thread, I'm tired of typing about it.
This was a used engine put in by Toyota with unknown mileage. Lasted a few thousand miles before this happened.

**EDIT**

Fairly certain I've determined what happened. This was clearly a junkyard engine. The front cover had been replaced but I wasn't sure why. I bet the car this from was in a front end collision. The trauma to the crank pulley probably translated to a crack in the crank sprocket.

[jrhudson]

thats what happened to mine. broken tooth and keyway of my crank sprocket. ill dig up the photos of mine in a bit.


i know what happened to where to part of crank sprocket gear broke. i left my ratchet with the 22mm on the crank pulley and started the car. so yea mine is installer error. (me)

[soundman98]

rockers don't just break. i suspect the pistons forced them backwards, maybe it jumped timing before?

[Turdinator]

My guess would be you spat a rocker and the valve train seized at least momentarily shattering the sprocket.

[Ultramaroon]

Perhaps over-torque of the crankshaft pulley screw started the crack and it grew until catastrophic failure. What are those marks on the end of the crank?

[DarkPira7e]

Thanks for your responses everyone. Just to be clear, I'm just looking to compile possible causes, I know there's no way to tell if the chicken came before the egg here. It's just something I hadn't seen mentioned here before so I thought a thread about it would be a good idea.

Originally Posted by Ultramaroon

Perhaps over-torque of the crankshaft pulley screw started the crack and it grew until catastrophic failure. What are those marks on the end of the crank?

This is what the tech at VEMS was thinking-that someone pounded the crank pulley on. What's funny is what when I removed the crank pulley after all this, it came off without even using a breaker bar, but that's likely because of the trauma. I'll be able to head there on Monday, I plan to get better photos from further away.
I am thinking that a rocker came off, upset the whole thing and caused a lot of damage in the 15 seconds it took me to get back to my driveway. This used engine they gave me had a strange noise I had believed to be the timing chain between 1600 and 2100 rpm, I would hear it on decel and on accel every time I passed through that RPM range with load on the car.

[blsfrs]

My engine guy and I think something hard got sucked into #3, floated the exhaust valves which chucked the rockers, which jammed the cam. My cam was actually bent. Gee, ain't we having fun.

[Ultramaroon]

Originally Posted by blsfrs

My engine guy and I think something hard got sucked into #3, floated the exhaust valves which chucked the rockers, which jammed the cam. My cam was actually bent. Gee, ain't we having fun.

Your failure is how I imagine the cascade would happen if it started with a jammed camshaft. A single link pin would shear way before the woodruff key on the sprocket, but the chain would stretch and break some teeth.

@DarkPira7e's initial failure was at the sprocket for sure.

[DarkPira7e]

@Ultramaroon I think I've pieced together a viable story. Engine may have been in a car that was involved in a front end collision. Timing cover had been replaced, maybe trauma to the crank pulley cracked the sprocket and it went unnoticed. It lines up with this being a junkyard motor that had the front cover taken off for some reason.

[Ultramaroon]

Originally Posted by DarkPira7e

Engine may have been in a car that was involved in a front end collision.

Yes! Augh!... Such a bummer. That's the last piece of the puzzle, though. Well done, sir.

[blsfrs]

Originally Posted by DarkPira7e

@Ultramaroon I think I've pieced together a viable story. Engine may have been in a car that was involved in a front end collision. Timing cover had been replaced, maybe trauma to the crank pulley cracked the sprocket and it went unnoticed. It lines up with this being a junkyard motor that had the front cover taken off for some reason.

The collision damage is plausible reason for the sprocket damage but we still don't have a good reason for the rocker arms ejecting.

[Ultramaroon]

Originally Posted by blsfrs

The collision damage is plausible reason for the sprocket damage but we still don't have a good reason for the rocker arms ejecting.

Pistons whacked the valves.

[Rabrooks]

I had a cracked crank gear. Not xactly sure of the cause but I blamed it on an ill fitting crank pulley. Are you running an aftermarket crank pulley?

[DarkPira7e]

Originally Posted by Rabrooks

I had a cracked crank gear. Not xactly sure of the cause but I blamed it on an ill fitting crank pulley. Are you running an aftermarket crank pulley?

No it was factory. Toyota had put this marvelous unknown mileage engine into my car as a fix for blowing up my previous 2 engines with the recall