Crank pulley seperation

[KC2SHO]

This looks like a good place to tell today's story.

This morning I started my 95 and heard a loud screeching. I thought it was the tensioner pulley or one of the idler pullyes going bad. I have plenty of used parts so I quicky pulled the battery, pulled the belt and inspected the pullies. Only one felt sligtly loose, the lower idler near the AC compressor. I replaced that pulley and reasembled everying, but no dice, the sound was still there. I pulled it back apart and upon closer inspection I found that the the two pieces of the crank pulley have seperated. The noise was the outer part of the pulley spinning on the inner part. I know what i'll be doing tonight.

 

[Black '93]

Wait, so your saying that the crank pulley broke, not in half, but in a way that separated the keyway part from the outer part or rest of the pulley?

 

[SHO Continental]

happened on my ATX too, except it didn't spin on it, the outer part pulled in toward the motor and ate up my lower cover, also the lack of alignment killed my AC clutch.

good luck :wave:

 

[KC2SHO]

Yes, It was in towards the cover, I'm not sure how much damage it has caused yet though. After I saw it I just shut the hood and borrowed my girlfriends car so I could get to work at a decent time. Funny thing though, I replced the AC compressor just a few weeks ago. I hope it didn't **** the replacment. SHOs are fun! And people wonder why I drink copius ammounts of alcohol.

 

[Black '93]

That's crazy! I've never heard of a SHO pulley breaking like that.. It kept running though?


Alcohol + Fast Cars= Fun!

DISCLAIMER: I will not be held responsible for anyones actions. I don't recommend drinking and driving.

 

[AREA 91]

I have read on the forum before, about the aftermarket ASP crank pulley doing the same thing. I believe that's why most that purchase UDP's, don't but the set that includes the crank UDP. Just my .01 cent....I spent the rest on my SHO's.

 

[KC2SHO]

It had some traction, enough to spin the accessories. I thought I heard something strange on the way home yesterday.

Edit: I'm considering dropping off the old one to have turned into a solid unit. I can't think of any reason why that would be a problem. what do you guys think?

 

[AREA 91]

If you make it a solid design, how will it dampen the engine vibrations/harmonics. It's not really a balancer, as our SHO's are internally balanced. Therefore it's really a crank pulley vibration dampener. Find a used one at a junk yard, or post in the WTB section on the forum.

Good luck, Brian

 

[KC2SHO]

It's all fixed drove it into work today.

witsimpala, It has no weighting and like you said our cars are internally ballanced. So, what is it dampening? Good aftermarket harmonic ballancers/dampeners for race cars that turn much higher rpms than our cars don't have rubber in them.

 

[AREA 91]

Correct. High end ones use a fluid inside them.

 

[KC2SHO]

Only for cars with external balancing?

 

[AREA 91]

Nope, both.

 

[KC2SHO]

I still haven't heard a valid argument for why I can't make it solid. I don't see how that 1/8" piece of rubber can save the internals of my engine. What is it protecting? Accessories don't put that much strain on the crank. If they did that rubber wouldn't have lasted 120k miles. Super charger kits don't even isolate the pulley from the crank and there is usualy a lot of strain there.

By the way if it wasn't for the 2 small bolts holding on the cover behind the pulley, it would have fallen farther back into the cover and it would have interfered with my timing belt. I should have taken pictures. The bolt heads are at least half worn off. They wouldn't have held out much longer. If I had waited any longer I would have have had a huge mess on my hands. Keep an eye on your crank pullys people! If you saw the potential for damage that I just did you'd be considering a solid one as well.

 

[AREA 91]

I'll try to explain the best I can. Internally balanced, means that the crank/rods/pistons are balanced by either adding or removeing weight from the crankshaft. Externally balanced, means that the balancer and either flywheel, or flexplate have weight added or removed to = a neutral position. Since our engines are internally balanced, all of the work has been done to the crankshaft. This means the balancer and flywheel/flexplate are neutral, or zero balanced. All of the hoopla ablove means you can put any 3.0 or 3.2 crank pulley on any 3.0/3.2 engine. An example is when you do a 3.2 "swap" into an mtx. You change out the single serpentine balancer for the 2 belt from a 3.0. No need to have the crank/rods/pistons rebalanced.

No on tho the "harmonics" of the engine. As the engine rev's through out its range of RPM, there are "frequencies" from the engine that need to be dampened. Hence the name dampener. A solid crank hub will do very little to dampen these frequencies, compared to a fluid filled, or elastomer (rubber) hub.

Several of GM's LT1 engines have had problems with the dampener seperating such as yours. The outer ring twists on the inner ring. This can cause all kinds of havoc, depending on the ignition system.

I hope this helps with an explanation.

 

[KC2SHO]

You didn't need to go into that level of detail for me. I've been building engines since I was 15. I still agrue that our "dampeners" don't dampen anything. The only issue I can see right now is maybe some vibrations can get into the pulley and cause some premature wear to the belt and even that's a stretch. That piece of rubber does nothing to save or dampen the internals of the engine. Anyway, my old one isn't even plyable anymore, it's more like hard plastic at this point. I'd bet most high miliage cars have the same condition. So why risk having it come apart again when I can take care of the problem once and for all?

 

[AREA 91]

Believe what you will.

 

[KC2SHO]

Hey I'm open minded but no one has been able to tell me why I can't do this yet.

 

[Minnesho]

That piece of rubber does nothing to save or dampen the internals of the engine.

oh really?

 

[KC2SHO]

Tell me why, no has been able to yet.

 

[Minnesho]

Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.

To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass and an energy dissipating element. The mass resists the acceleration of the vibration and the rubber/clutch/fluid element dissipates the energy of vibration.

There has been a trend at times by some "performance enthusiasts" to remove the harmonic balancers on their cars. The argument is that they aren't necessary and their mass reduces the performance of the engine. This is not true however as most vehicles see an increase in power when fitted with a proper harmonic balancer; in addition the risk of destroying the entire engine is too high for the marginal gain that might be realized by removing the harmonic balancer.