► ► OH MY GOD, MY CRANK PULLEY SPUN...WHAT NOW? @ CoW ◄ ◄
03-01-2009, 01:09 PM
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St. Jude Donor '07-'08-'09-'10-'12-'13-'14
► ► OH MY GOD, MY CRANK PULLEY SPUN...WHAT NOW? @ CoW ◄ ◄
OH MY GOD!
My CRANKSHAFT PULLEY (balancer) SPUN!!!
WHAT NOW?!?!?
By now, most of us have figured out that this is a somewhat common problem with late Corvettes. The crank pulley (balancer) retaining bolt is "torque to yield" and as large a bolt as it is, and despite it's intended engineering whatever, It's not much more than a "cash cow" for GM as every time this bolt is removed...you MUST replace it. It's been causing millions of dollars of warranty issues for them and likely an equal dollar amount of distress for corvette owners not still covered under the general's warranty.
Engines of yesteryear used "REAL BOLTS" where you could make em' tight and re-use them over and over....Kinda like an ARP bolt that has an almost infinite lifespan....provided you don't over stretch it. The cylinder head bolts on LSx engines are also torque to yield, and YES, You have to replace them EVERY TIME as well.
Also, these engines are balanced differently than earlier engines so that the crank pulley can go on any way you like....You'll notice there is NO CRANK KEY like your old small and big block chevy had. The keyway was kinda nice because it helped index the pulley and kept it from spinning on the nose of the crank.
Recently, I got a call from a customer named Mike with an 05 C6 mn6. He was in a panic because he felt that his balancer had spun and it was making a "chirping" sound.
Knowing how serious this can be...I advised him NOT to drive or start the car and get AAA to tow it to the shop. When the car arrived, his pulley had a very noticeable "WOBBLE" to it and it was, like he said, CHIRPING.
Here we go... After lowering the front chassis...and removing the steering rack....We removed the pulley.
TO MY SURPRISE...The CRANK was PERFECT!
What happened was the outer ring of the (let's use the correct term here) ELASTOMETER had misaligned from the crank hub and made the pulley wobble causing the belt to chirp like a bird.
Mike (and I) kinda thought he was looking at a crank job at the least and possibly that expensive high compression stroker motor with the new "CoW CAM"....This time, that option was not in the budget.
I called mike and explained that everything was cool....The simple fix here was a nice underdrive pulley and a slightly shorter belt with a NEW bolt. Bada BING! Fixed! A quick FREE RE-TUNE and some extra horsepower...and Mike was off to the races with a smile.
Mike got off REALLY EASY. EVERYONE, take note here... DO NOT DRIVE YOUR CAR IF YOU SUSPECT YOUR BALANCER HAS COME LOSE!!! While we would like all stories to end as nicely as his did, there is a darker side to this problem....
ABOUT 2 WEEKS AGO....
...This nice guy named Tim brings his C5 from Michigan all the way to Corvettes of Westchester for a clutch and some tuning.
My guys begin to dismantle the drivetrain when Tim mentions his crank pulley had previously spun and was wobbling AGAIN!
OH JEEZ...Here we go again. Having recently repaired an H2 HUMMER with a supercharger (successfully) and saved the motor....I figured I was in for another battle to the death.
As we started to remove stuff from the car....The situation got worse and worse.
First the crank pulley...NOT GOOD. Then the waterpump and timing cover...OH MY GOD!..... next...The oil pump....DIDN'T WANNA COME OFF!!!
Tim, my friend, We'll take good care of her...You'll have to leave here here for a few weeks....I said.
Below is a hand full of photos showing the dangers of a "SPUN PULLEY".
We took these photos with our new high powered "CoW CAMera" he he...
Have a look....These photos show how the metal from the CRANK and PULLEY get into the oil pump and circulate through the entire engine destroying the oil pump, crankshaft, bearings, and pistons not much unlike cancer.
DO NOT IGNORE THE WOBBLING PULLEY PROBLEM!
THIS COULD HAPPEN TO YOU.
STAY TUNED FOR THE re-BUILD UP OF TIM's NEW CAMMED STROKER MOTOR WITH THE BLOWER...Later in this thread...
FIRST...THE METAL DEBRIS IN THE BEARINGS...
Here's the nose of the crank with the oil pump drive... This crank was "PINNED" once and it failed....then drilled for a second crank pin.... Looks like a PIT BULL chewed on it...
Here's the metal in the main bearings...
The oil pump took some "HEAVY METAL" and nicely distributed it throughout the motor...
Finally, the metal from the pulley and crank nose actually got up into the pistons...
There you have it. Be sure your shop DOES NOT RE USE the crank bolt. USE LOCTITE! and if possible....Use a quality "CRANK PINNING" kit to drill and dowel (index) the pulley so it can not spin....ESPECIALLY for forced induction cars where the blower is driven from the crank pulley.
Again, of you suspect your crank pulley has come lose....HAVE SOMEONE competent check it out for you.
Left unattended...this can become an expensive MESS!
As Tim's vehicle goes back together we'll post the progress in this thread.
STAY TUNED!
CHUCK CoW
03-01-2009, 01:41 PM
#3
If you do a search Most good tuners say now that the manual cars are breaking Timing chains when installing the under drive pulley. They say its causing harmonics issues
:b igears
:b igears
03-01-2009, 03:55 PM
#5
Melting Slicks
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Chuck I swear to god, when I first saw this thread I thought it was going to be about Cameron's car.
Is this mainly a problem for C5 and '05 C6s? Wasn't it a TSB for the 05s? Do you know what, if anything, GM did to prevent this on the '06+?
03-01-2009, 08:09 PM
#6
Safety Car
I agree, Frank. Thousands of UD pulleys installed in LS motors, only a few reported broken chains, and almost every one of then found to be another cause....if it were the UD it would be epidemic. If harmonics were a problem, GM would be in serious trouble as they don't balance things out well to begin with.
I knew it wasn't Cam's car though, it would be tearing up the road right now if not for the weather, but now I know why Chuck never showed up for dinner.....nice pics and info.
I knew it wasn't Cam's car though, it would be tearing up the road right now if not for the weather, but now I know why Chuck never showed up for dinner.....nice pics and info.
03-02-2009, 01:07 AM
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St. Jude Donor '07-'08-'09-'10-'12-'13-'14
Cameron's car???? NOPE. he he
I don't believe it has been officially traced back to an UD pulley. It was just a theory that some had thrown out there to find the true cause. However new info may have developed that I'm not aware of.
Chuck I swear to god, when I first saw this thread I thought it was going to be about Cameron's car. Is this mainly a problem for C5 and '05 C6s? Wasn't it a TSB for the 05s? Do you know what, if anything, GM did to prevent this on the '06+?
Chuck I swear to god, when I first saw this thread I thought it was going to be about Cameron's car.
Is this mainly a problem for C5 and '05 C6s? Wasn't it a TSB for the 05s? Do you know what, if anything, GM did to prevent this on the '06+?
I see more of this balancer stuff with C6's for some reason and ANY blower car that's not pinned right.
The other primary reason is mechanics not realizing that the bolt is NOT re-usable. That's a sad mistake, but it happens.
I really believe that GM doesn't make em tight enough...How many times have wee seen this before?
(lug nuts and axle nuts, etc)Chuck CoW
03-02-2009, 05:43 PM
#10
Burning Brakes
Good write-up and great pics. It just makes sense for GM to re-implement the crank key, good grief, how stupid is that to not do it?
I'm going assume that an intelligent mechanical engineer did not come up with the idea to eliminate the crank key, but it was management. I have worked for a couple of engineering firms in the past witnessing this same type of crap....managers that think they know more than the engineer (and the managers are not degreed in engineering); "....hey, let's save some money and take a step backwards in design...good idea, huh?"
I'm going assume that an intelligent mechanical engineer did not come up with the idea to eliminate the crank key, but it was management. I have worked for a couple of engineering firms in the past witnessing this same type of crap....managers that think they know more than the engineer (and the managers are not degreed in engineering); "....hey, let's save some money and take a step backwards in design...good idea, huh?"
