Crank Pulley Key butchered - common problem?

[tsupranami]

Anyone else ever have this problem? I've had two motors eat their cranks away with the harmonic balancer pulley/key.

The harmonic ballancer (crank pulley) was wobbling around, back and forth, up and down, sounding like a main bearing knock. The bolt was fully tightened, it took a HUGE extension bar and a massive 4ft. long homemade pulley holder to break it free. But the balancer just slid right off after that, revealing the uglyness pictured below.

Now the crank is thoroughly buggered...maybe a weld and grind could fix it. Any suggestions?

 

[shaeff]

My bet is that it wasn't actually torqued to 195ft lbs like it should have been. How do the threads on the bolt and in the crank look? It's not that common of a problem, but I've come across it before. I was forced to cob-job fix it, as the person I was helping didn't have the money for a full rebuild at that time (and I didn't have the time to pull the motor again)

The cob fix worked until he popped the motor, though.

Your best bet is to pull the crank and either source a new one, or get it welded up at a competent machine shop. Hopefully others who are more knowledgeable than me will chime in. (jdub, IJ., figgie, etc...)

 

[GrimJack]

Yes, this is a reasonably common occurrence. Can be fixed with a weld and recut, but it's a PITA to do. Never seen anyone get away with doing it in the car, so you're looking at pulling the engine.

Alternatives are a new crank or getting the one that you have recut 180 degrees out.

 

[Mk3runner]

got the exact issue with a 7m that I'm working on right now. basically I wanna rig it to run since the crank is crap. just want it to hold up till a rebuild is allowed, no hard driving.

just cant figure a solid take on it just yet. I got a idea to build it up with a stock key and jb weld but idk.. I dont take to *rig* jobs well. I like proper and no need to go back and keep dicking with it.

on another note on my 7m I torqued to 195. but once outta storage I'm going to go back and retorque the head and the crank pulley for good measure lol.

 

[zambini]

yep thats what happened to me last year, except my key was folded in half and in two or more pieces (basically disintegrated lol).. its pretty crazy that your key is still in such good shape. you'd think the key would deform more than the crank snout, but it looks like somebody made an impression in modeling clay. i didnt mess with the idea of welding and grinding it.. apparently since 7m's are inline 6's, the bearings are so supersensitive that even one of the billet aluminum harmonic balancer replacement pulleys are enough to kill the bearings since the crank is so long.. so if a perfectly cnc'd pulley wont keep the crank balanced, i didnt want to trust a ground down weld to fix my crank at the key.. of course i kinda accepted the fact that my engine was pooped either way. the crank would have to be popped out to be replaced, which means new bearings.. the crank being jerry rigged would eventually kill the bearings.. so i got a rebuilt engine and swapped it.

sorry if this is wordy im kinda drunk, but i feel your pain man.

 

[tsupranami]

Wow, I had no idea that it was so common.

What seems to be the main culprit? Undertightened pulley bolts? Modified motors revving too fast for all the belt drives to keep up? Inherent design flaw of the multiple accessory belt system - long pulley with large leverage forces from accessory belt tension(one reason serpentine belts are used now - less leverage on a shorter crank snout and pulley)?

I did a new OEM shortblock on the wife's car, and I am using a reground crank on mine. I'm gonna ditch the fan and clutch and go electric, so some parasitic drag and inertial resistance should be removed from the crank pulley that way.

New harmonic balancers w/new bolts are on both, so hopefully I wont see this again for a while.

I'm just paranoid about it happening again...

Anyone have tips or tricks to prevent it?

 

[IJ.]

yep thats what happened to me last year, except my key was folded in half and in two or more pieces (basically disintegrated lol).. its pretty crazy that your key is still in such good shape. you'd think the key would deform more than the crank snout, but it looks like somebody made an impression in modeling clay. i didnt mess with the idea of welding and grinding it.. apparently since 7m's are inline 6's, the bearings are so supersensitive that even one of the billet aluminum harmonic balancer replacement pulleys are enough to kill the bearings since the crank is so long.. so if a perfectly cnc'd pulley wont keep the crank balanced, i didnt want to trust a ground down weld to fix my crank at the key.. of course i kinda accepted the fact that my engine was pooped either way. the crank would have to be popped out to be replaced, which means new bearings.. the crank being jerry rigged would eventually kill the bearings.. so i got a rebuilt engine and swapped it.

sorry if this is wordy im kinda drunk, but i feel your pain man.

Drunk and Clueless

Think of a front pully as a shock absorber for the crankshaft, each time a cylinder fires it twists end to end and the Damper catches that, this is why the bullshit CNC pulley's are junk.

Wow, I had no idea that it was so common.

What seems to be the main culprit? Undertightened pulley bolts? Modified motors revving too fast for all the belt drives to keep up? Inherent design flaw of the multiple accessory belt system - long pulley with large leverage forces from accessory belt tension(one reason serpentine belts are used now - less leverage on a shorter crank snout and pulley)?

I did a new OEM shortblock on the wife's car, and I am using a reground crank on mine. I'm gonna ditch the fan and clutch and go electric, so some parasitic drag and inertial resistance should be removed from the crank pulley that way.

New harmonic balancers w/new bolts are on both, so hopefully I wont see this again for a while.

I'm just paranoid about it happening again...

Anyone have tips or tricks to prevent it?

Most times it's Dipshits with rattle guns that don't think a Torque Wrench is needed for anything..... :nono:

 

[mkIIIman089]

Drunk and Clueless

Think of a front pully as a shock absorber for the crankshaft, each time a cylinder fires it twists end to end and the Damper catches that, this is why the bullshit CNC pulley's are junk.



Most times it's Dipshits with rattle guns that don't think a Torque Wrench is needed for anything..... :nono:

Good post.

This problem is only common for idiots... to answer the title question.

 

[Poodles]

Not to mention loose bolt will screw the threads over time...

 

[Enraged]

how can you hold the crank pulley while torquing the balancer bolt? it won't hold with the car in gear, just turns the motor. is an SST required or is there an easier/different way of holding it?

 

[CyFi6]

good luck dude i have a crank here and it has the same issue but seems worse. The snout where the crank pulley goes is .015" smaller than its supposed to be and the bolt that goes in the end of it rocks back and fourth in the crank a crazy amount from being rapped back and fourth in there with the engine running. The crank is junk i wouldn't spend any money to fix it, just replace it.

 

[zambini]

Drunk and Clueless

Think of a front pully as a shock absorber for the crankshaft, each time a cylinder fires it twists end to end and the Damper catches that, this is why the bullshit CNC pulley's are junk.

thus making the bearings deteriorate right? because there isnt enough dampening with the cnc'd pulley..

so a weld and grind would have to be perfect in order to keep the crank balanced, no? or is it not as much of an issue because it's inside the harmonic balancer?

 

[Enraged]

the crank would need to be rebalanced after cutting and welding the snout.

 

[Mk3runner]

at the point just source a new crank.