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Harmonic Balancer Bolt Fell Out - Loss of Another Engine

47K views 90 replies 31 participants last post by  RalphP 
#1 ·
Unfortunately, I have another lesson learned to share with you all that lead to the loss of my 2nd motor.

All the details are in my Runoffs race report:
http://www.z06vette.com/forums/showthread.php?t=68415

Lesson learned: The service manual does not specify putting any locktite on the harmonic balancer bolt (the main pulley on the end of the crankshaft). Apparently, when taking this bolt in and out, it doesn’t stay in as well as it does from the factory, and when it comes out the results can be catastrophic.
Recommendation: If you take this bolt out for any reason, such as putting on an underdrive pulley, putting in a cam, etc, put locktite on the new bolt.

The service manual procedure is to use the old bolt to press on the harmonic balancer (pulley) with a torque of 240 ft-lbs. Then remove the old bolt and put in a new one, torquing it to 37 ft-lbs, then rotating it another 140 degrees (which we measured to take on the order of 250 ft-lbs). New bolts do not come with locktite on them as do other new bolts like the brake caliper bracket bolts.

We took the motor apart to refresh it prior to the Runoffs. The above factory procedure was followed when the balancer was put back on. This had been the third time this motor had been apart. The first being when we inspected it from the factory. The second after a timing chain failure earlier this year.

On my 3rd lap of practice the bolt came out, allowing the balancer to warble around on the front of the crankshaft, wearing the inner edge of the balancer to a 45 degree angle and scoring the heck out of front of the crankshaft. Oil sprayed all over the front of the motor from leakage around the oil seal behind the balancer. Remarkably, the belt stayed on the balancer though it wasn’t spinning much as I lost power steering. The bolt itself did not fall off the car because it couldn’t back all the way out as it hit the power steering rack before coming completely out of the crankshaft.

It took us a day to smooth the front of the crankshaft, replace the oil seal and install a new balancer.

The car ran fine in the pits, but after two turns on the track as rpms were gradually raised, the engine lost oil pressure, with pressure dropping to 25 psi or so. After a quick check in the pits, and a return to normal 40 psi at idle, I went back out (bad idea) and the engine totally lost oil pressure and died after a half lap. While we didn’t have time to take apart the motor and see exactly what went wrong, we did see that there is a 2” diameter hole in the side of the block at piston 2, and piston 1 came up and smacked the bottom of the head.

Based on the damage at the front of the motor and loss of oil pressure suspect that we either:
- scored a bearing when metal shavings entered the motor when the balancer flopped around on the front of the crankshaft
- or slightly bent the crankshaft leading to damaged bearings when the balancer flopped around on the front of the crankshaft

After my bolt came out, I talked to at least three other T1 drivers who had this same problem and now used red locktite. I suspect that the more times the balancer comes on and off, the more likely it is for the bolt to back out. Thus, for the vast majority of you with stock motors that have never been worked, I wouldn’t lose any sleep over this. But for those of you who have made mods to your motors that are likely outside the warranty, like underdrive pulleys, I would recommend putting red locktite on the bolt when you put the new one in.

For those that have had your bolt out already, you might want to check to make sure it hasn’t backed out any.
 
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#4 ·
Subdriver, is your Harmonic Damper Pulley pinned (AKA keyed, Woodruff Key, etc.) to the Crank?

Mine is, courtesty of the Vortech install. I wouldn't expect the bolt to back out if the assembly is keyed together, so I'm trying to figure out whether or not I might need to go crawl under the car and give it a look.
 
#7 ·
I had my damper bolt loosen twice, both during racing, on my 01. Both times the dealership just tightened it down and said it should be fine! Due to other problems I was having with the car, I traded it for an 04.

I probably won't have this one keyed, but it sure makes me think!

Justin
 
#9 ·
very sorry to hear this ....i myself lost a timming chain last year and it destroyed everything....dont give up...
 
#10 ·
RocketSled said:
Subdriver, is your Harmonic Damper Pulley pinned (AKA keyed, Woodruff Key, etc.) to the Crank?
Stock, the LS6 balancer is not keyed to the crank. By SCCA T1 rules, my engine must remain stock, so no, it is not keyed.

Due to other problems I was having with the car, I traded it for an 04. I probably won't have this one keyed, but it sure makes me think!
My thought is that the balancer fits on the crank less tightly with each case of taking it on and off. If you haven't touched your 04, I wouldn't worry too much about this.

i myself lost a timming chain last year and it destroyed everything....
Been there, done that to... :(
http://www.z06vette.com/forums/showthread.php?t=61443&highlight=timing+chain
 
#11 ·
Subdriver said:
Stock, the LS6 balancer is not keyed to the crank. By SCCA T1 rules, my engine must remain stock, so no, it is not keyed.
How is keying the crank more of a "mod" than non-OEM tires or wheels or a low restriction air filter or any number of other mods? It's not an internal engine modification, it doesn't affect operating HP in any way. That seems like a damn stupid limitation!
 
#12 ·
RocketSled said:
How is keying the crank more of a "mod" than non-OEM tires or wheels or a low restriction air filter or any number of other mods? It's not an internal engine modification, it doesn't affect operating HP in any way. That seems like a damn stupid limitation!
The non-OEM wheels, tires etc are all specifically allowed for in the SCCA T1 rules, usually by exact part number (such as DRM radiator part number 30-695).
The key "mod" is currently not legal, but you are correct, there is no good reason for it not to be made legal. I intend to request a rule modification to allow it. The SCCA usually will grant this type of rule change as soon as someone asks for it, which is how we got oil and tranny coolers, etc all made legal.
:cheers:
 
#13 ·
I Locktight, flywheel bolts, pressure plate bolts, crankpulley bolts and any other bolt that spins and is important.
I know I locktighted my crankl bolt but I could have sworn that the bolt came with some kind of red crap on the threads. Maybe I am wrong as it was a year ago.
 
#16 ·
Redshift said:
Had the same problem with my bolt THREE TIMES after a cam installation. Turns out we had to torque down higher than 240 (I think we did 275lb-ft as recommended by the manuf) and then used Loctite. Good tip, and thanks for sharing. :cheers:

3 time is a charm for me yesterday as well :bmad: :bmad:

had to have the car towed :mah:
 
#21 · (Edited)
IT L GO said:
That's not true :roll:
In case you missed it, it was a question not a statement :roll: :roll: :roll:

From the Permatex web site: Formula 271 (found in most Autozone stores): "OEM specified. High strength threadlocker for heavy-duty applications. Especially well-suited for permanently locking studs and press fits. Adds 3,000 PSI holding power on slip and press fit assemblies. Replaces set screws and snap rings. Locks against vibration loosening. Requires extra effort or special tools for removal."

Formula 262: "OEM specified. A permanent, high strength product that is applied to fasteners 3/8" to 1" (10mm to 25mm) in size before assembly. Designed for securing parts that must withstand heavy shock, vibration, or extreme chemical or environmental conditions. Localized heating and hand tools are required to separate parts."
 
#25 ·
gmblack3 said:
I think there are 2 different kinds of red loctite. One is for permanent applications and the other is not.
There are in fact many types of Loctite. 100s. There are adhesives for all sorts of different applications. Thickness, set time, bond strength, you can dial them all in for a particular application. Stuff that dries quick or slow, stuff that is anerobic, stuff that stays gooey, stuff that hardens like steel, stuff that hardens like glass, you name it.
 
#26 ·
Sorry to hear about your motor...now I need to check my car out to make sure the bolt is in place. Thanks for the heads up! :z:
 
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