Anyone ever had the crank pully back out?!
07-24-2007, 08:02 PM
#2
Team Owner
Has anyone ever had this happen before?
It's happened many times to both C5's and C6's.
Does this pully also serve as the harmonic balancer for the motor?
The motor is internally balanced at the factory so the crank pulley is basically a vibration damper.
Is there any chance that I've stripped any threads or busted anything else?
The bolt that held it in may have loosened and backed out but there's a good chance the threads in the crank snout are intact. The bolt cannot fall out unless the rack moves out of the way and the pulley would need to break/disintigrate to fall off so you're probably OK. The steering rack is going to look like hell when you pull it (or your mechanic does) but it should survive if there are no cracks, etc.
Anything I can do to prevent this from happening again?
Pin the pulley to the crank snout with two dowels using a pinning kit. I hope whoever put in your TT setup also pinned your pulley. That kind of torque is sure to loosen your pulley if it's not pinned. It's SOP on all the S/C setups. I would pin any pulley in a C5 if I had access to it - even on a stock car. It's that common and very easy/cheap to do so it's cheap insurance. Here's a shot of a pinned pulley we did on my buddy's S/C C5.
Another thing many do is to improperly install and torque the pulley to the snout. Factory procedure is to torque the new pulley on with the old bolt first (which you throw away after as it's a torque-to-yield one-time-use bolt unless you buy the ARP crank bolt) to 240 lb. ft. This serves to push the pulley on to the crank snout a certain distance with a tolerance spec'ed in the drawing below.
The dimension shows the proper distance from the indicated face of the pulley to the end of the crank snout. That ensures proper alignment of the crank pulley to the other pulleys and belts. Next, the new bolt is threaded in and torqued to 37 lb. ft. Finally the bolt is torqued another 140 degrees. This is where the bolt is stretched to put it in tension and hold the pulley in place. The pulley is not keyed to the crank snout so it's important to acheive this tension if the pulley is not pinned as pictured above. Here's a shot showing my underdrive pulley after I did the final torqueing. Note the marks on the pulley and bolt head to indicate the 140 degrees the bolt was torqued to. I did not pin mine back then because I did this several years ago before pinning came about due to slipping pullies caused by the new S/C kits. I will be doing it if I ever pull the steering rack again for any reason.
The time to pin it is just before threading the new bolt in and you have access to the pulley and crank snout ends at the same time to drill for the dowels.
Best of luck in your repair.
It's happened many times to both C5's and C6's.
Does this pully also serve as the harmonic balancer for the motor?
The motor is internally balanced at the factory so the crank pulley is basically a vibration damper.
Is there any chance that I've stripped any threads or busted anything else?
The bolt that held it in may have loosened and backed out but there's a good chance the threads in the crank snout are intact. The bolt cannot fall out unless the rack moves out of the way and the pulley would need to break/disintigrate to fall off so you're probably OK. The steering rack is going to look like hell when you pull it (or your mechanic does) but it should survive if there are no cracks, etc.
Anything I can do to prevent this from happening again?
Pin the pulley to the crank snout with two dowels using a pinning kit. I hope whoever put in your TT setup also pinned your pulley. That kind of torque is sure to loosen your pulley if it's not pinned. It's SOP on all the S/C setups. I would pin any pulley in a C5 if I had access to it - even on a stock car. It's that common and very easy/cheap to do so it's cheap insurance. Here's a shot of a pinned pulley we did on my buddy's S/C C5.
Another thing many do is to improperly install and torque the pulley to the snout. Factory procedure is to torque the new pulley on with the old bolt first (which you throw away after as it's a torque-to-yield one-time-use bolt unless you buy the ARP crank bolt) to 240 lb. ft. This serves to push the pulley on to the crank snout a certain distance with a tolerance spec'ed in the drawing below.
The dimension shows the proper distance from the indicated face of the pulley to the end of the crank snout. That ensures proper alignment of the crank pulley to the other pulleys and belts. Next, the new bolt is threaded in and torqued to 37 lb. ft. Finally the bolt is torqued another 140 degrees. This is where the bolt is stretched to put it in tension and hold the pulley in place. The pulley is not keyed to the crank snout so it's important to acheive this tension if the pulley is not pinned as pictured above. Here's a shot showing my underdrive pulley after I did the final torqueing. Note the marks on the pulley and bolt head to indicate the 140 degrees the bolt was torqued to. I did not pin mine back then because I did this several years ago before pinning came about due to slipping pullies caused by the new S/C kits. I will be doing it if I ever pull the steering rack again for any reason.
The time to pin it is just before threading the new bolt in and you have access to the pulley and crank snout ends at the same time to drill for the dowels.
Best of luck in your repair.
Last edited by Patches; 07-24-2007 at 08:55 PM.
07-25-2007, 03:24 PM
#5
Burning Brakes
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St. Jude Donor '07
Not for nothing, but you are telling me the LS1 crank drive pulley is retained on the snout of the crank by BOLT TENSION ONLY? THERE IS NO WOODRUFF KEY IN THE CRANK ENGAGING THE LOAD OF THE BELT DRIVE? That's an accident waiting to happen!!! That's downright SCARY ENGINEERING!!!!!! WTF!
John
John
07-25-2007, 04:15 PM
#6
Le Mans Master
07-25-2007, 05:25 PM
#7
Melting Slicks
It is not bolt tension only. It is a press to fit. The pulley is actually stretched over the snout of the crank. The bolt backs out when this tension is broken and the pulley begins to rotate on the snout.
It is why I would never re-use a damper/balancer (stock or otherwise) that has been stretched on. I would re-use a balancer if it was keyed or pinned.
Purchase a new one from either ASP, Powerbond or ATI. I would not use a stock pulley. They have other issue relating to wobbling and failure of the rubber layers. I know this one all too well.
It is why I would never re-use a damper/balancer (stock or otherwise) that has been stretched on. I would re-use a balancer if it was keyed or pinned.
Purchase a new one from either ASP, Powerbond or ATI. I would not use a stock pulley. They have other issue relating to wobbling and failure of the rubber layers. I know this one all too well.
07-25-2007, 08:05 PM
#8
Team Owner
I agree with Gonbad that it has a few thousandths press fit. I got aluminum shavings when I have pressed a couple of ASP pulleys on. The bolt head pushing back on it is what keeps it from walking forward when the crank spins it, despite the press fit.I also agree that I would go aftermarket if I were replacing mine - probably the ATI version if I were doing it now. And I would never reuse a pulley even if it had been pinned since the elastomer is partially fatigued and heat cycled. Too much work to get to it if it fails.
07-26-2007, 05:48 PM
#10
Burning Brakes
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St. Jude Donor '07
Yeah, but my problem is these cheap SOB engineers at GM HAVE THE ***** to pull this s**t. Its probably not the engineer's it's probably GM's F**KING accountants.....as usual. This kind of stuff should NOT BE COMPROMISED, that's why I'm a Ford guy. I've been preaching this stuff for years!!!!!! I think, (pardon me I'm new at this) that GM people TOLERTATE THIS KIND OF S**T! I will complain, YOU SHOULD TOO!!!!!
GM CUSTOMERS NEED TO COMPLAIN ABOUT COST CUTTING QUALITY!
Then maybe, we'll have world class quality! Don't take this the wrong way , but if FORD had a vehicle with the CLB problem, it would be fixed in one year of production. Not overlooked completely!!! I love buying a Ford product, 2 years later than the model I have, because all the S**T I hated on the earlier model HAS BEEN FIXED!!!!! Sorry, I love my Corvette, just new to the GM experience, just venting!!!!
John
GM CUSTOMERS NEED TO COMPLAIN ABOUT COST CUTTING QUALITY!
Then maybe, we'll have world class quality! Don't take this the wrong way , but if FORD had a vehicle with the CLB problem, it would be fixed in one year of production. Not overlooked completely!!! I love buying a Ford product, 2 years later than the model I have, because all the S**T I hated on the earlier model HAS BEEN FIXED!!!!! Sorry, I love my Corvette, just new to the GM experience, just venting!!!!
John
09-04-2012, 02:59 PM
#11
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There is another alternative to "pinning". It's very similar. The hole is still drilled in the crank shaft and the balancer hub, but the hole is then tapped. Use an allen set screw with blue loctite 243. This retaining procedure is called a "dutchman".(not sure why) I am in the industrial engineering field and this procedure has worked well for many years. One other way is a pin set in the thick washer. The pin and the crank bolt then would have a small hole drilled through them so that stainless steel avaition wire can be threaded through. This is used in the aircraft industry where a bolt coming loose is deadly.
