JimMueller

iTrader: (9)

Thursday night I left work and when I started the car and drove off, I noticed the engine was running rough and once I got the RPMs into the upper teens it lacked power and shuddered a bit. I figured it was a broken valvespring, but I didn't get any SES. I didn't get the SES because I had my misfire tables desensitized (not disabled, just desensitized enough to stop the random P0300's I would get with the cam). I gently drove it home 6 miles through residential streets.

Once home, I put the misfire tables back to stock and drove around the block monitoring current and history misfires on all cylinders. Cyl6 would climb above 100 and then reset to 0, the other cylinders didn't report a problem. Called my tech and was able to get in the race shop early Friday morning, so I gently drove 6.5 miles to the shop. I wasn't using the scan tool while driving, but I eventually received an SES and it would sometimes blink indicating the misfire detection.

They duplicated the concern on cyl6. Moved #6 coil to #4 and #6 spark plug to #2, and went for a drive down the street to see if the problem switched cylinders. As they were coming to a stop, they lost the power steering. My tech drove it across the intersection and looked at the front of the engine. Serpentine belt was off, and the ATI harmonic balancer had come off the front of the motor; it was balanced between the sway bar and radiator. He drove it back the short distance and back on to the lift and says that while it got hot it did not overheat.

We drove another vehicle up the same path and could not find the bolt, so the bolt had to have come off in the recent past and that initiated the misfire condition.

I already had two new GM crank bolts in storage so he loaned me a vehicle to go home to get the bolts and he picked up a new crank seal as well. When I got back, the ignition cylinder I had to nurse back to life a few months ago came apart again. So back home I went to get my new ignition switch and then over to a TrueValue store that had just one of the correct VATS keys remaining that matched my car.

The tech replaced the crank seal & crank bolt, torqued to 240 with a SnapOn wrench and used blue loctite, and also replaced the ignition cylinder. We topped off the water/redline mix I run with a bit of coolant because the shop didn't have what I used on hand. Performed a crank relearn and he took it for another test drive, all seems back to normal. On the way back home, it seemed as if I had a bit of new tapping noise echoing off other vehicles on the driver side, but perhaps it was my imagination.

This morning I checked the water level and it was a little low. I started the motor, maxed out the heat and let it idle for about 25 minutes. By the time I was done, it accepted another 12oz of Water Wetter.

To my knowledge, that crank bolt hasn't been touched since it was installed back in June 2010. We've never had the crank pulley off, but I did have a cracked PS bracket a year or so ago and I had to replace it with an aftermarket billet solution because I couldn't find an OEM bracket. I think we may have replaced an idler pulley in that time. I just don't understand what might cause the crank pulley to back out.

Any ideas on what would cause the crank bolt to work its way loose? Anything else you would check for peace of mind?

JimMueller

iTrader: (9)

Could whatever it was that caused the bolt to be loose or loosen over the years cause a performance problem? Maybe it's just a placebo, but since replacing the bolt & seal, the car seems a bit livelier.

dreadpirateroberts

iTrader: (1)

the performance problem was likely the harmonic balancer not being able to do it's job. it's mated to the crank snout via an interference fit, and once it it started to slip off, that "bond" was gone and it was probably vibrating back and forth on the snout instead as it worked it's way off.

as far as the crank bolt walking out, not being torqued on enough to begin with might be likely. as long as the crank snout threads are fine, and the harmonic balancer isn't damaged or the rubber rings in it aren't worn out and the unit needs a rebuild, make sure the balancer is seated and a new bolt is torqued to spec.

DietCoke

iTrader: (18)

...loctite on a new crank bolt?

rip.

Darth_V8r

iTrader: (4)

As to how it came loose -- perhaps that inner crank seal got broke on install and motor oil lubed the threads over the course of time along with vibrations?

MuhThugga

For a stock bolt, you are supposed to use the old bolt to torque to 240 ft/lbs, install the new bolt, torque to 37 ft/lbs, and then an additional 140 degrees.

JimMueller

iTrader: (9)

Yes, blue loctite used on new bolt. I provided two new stock crank bolts, but we obviously lost the original. I do not know what method was used to torque the new bolt down, I'll ask.

Billiumss

iTrader: (11)

I use Red Loctite on the GM crank bolt, never had any issues. Just follow GM's install procedure. Even when I took "my" bolt off when working on someone's car again, it was tight like you would expect.

Mavn

iTrader: (3)

red locktite and a 1/2" Impact does the trick

JimMueller

iTrader: (9)

He just texted me that he used 240 with a new stock bolt and blue loctite and claims I'm all set. What's the effective difference between the procedure provided by their online vendor and the factory procedure?

06GR

I'd like to know that as well. I used an ARP bolt, their moly-lube and 235lbs.

Millenium Z06

I used the ARP moly and bolt and had it back off twice after torquing it down to 240 then 250lbs. Used Red 262 the 3rd time and put witness marks on the bolts so I just have to glance at it.

1 ARP instruction set says to uses 262, another says to use the ARP lube

ChopperDoc

When you start changing out dampers and parts like that, I would say pinning the crankshaft isn't a bad idea. I know anything in the 500 whp range is definitely recommended for pinning. Then just install a new bolt (after seating the damper with the old one), torque to 37 ft lbs, and then 140*. It is A LOT of extra torque.

When I recently did mine for a cam swap, I broke a 1/2 x 24" breaker bar into a bunch of pieces, which I had to find, since my valve covers were still off. I found all the pieces thankfully. I made it to about 110*, but I have a keyway so I'm calling it good lol. No Loctite or issues at all. Just an OEM bolt in there with an ATI damper. High HP will spin the damper, or even just a lot of spirited driving over time. I wouldn't call this out of the ordinary.

By the way, the breaker bar was a Gear Wrench, so, buyer beware? Or I just had too many Wheaties that morning... In any case, mine is plenty tight I think.

06GR

Why did you have to back it off twice? Did it come loose?

Millenium Z06

Yes, backed off twice. The last time I keyed the balancer and the crank and used red 262, wasnt doing it again. So far, 1 year+ and no issues

06GR

Damn, I need to keep an eye on mine then.

MuhThugga

The GM bolts are TTY, and the process is as I stated earlier. The 240 ft/lbs on the old bolt is specifically for ensuring that the balancer is fully seated. The 37 ft/lbs plus 140* is for the new bolt.

ARP is 240 ft/lbs. The ARP bolt is also not TTY.

If a GM bolt was used, the effective difference is the procedure. The angle is going to be much more accurate than the torque rating. If the torque wrench is off, the threads weren't clean, or something else was present along those lines, the wrench could read 240 ft/lbs before the bolt actually hit the specified angle.

JimMueller

iTrader: (9)

Would it be reasonable to buy an ARP crank bolt, confirm my current crank bolt is still at 240ft-lbs, then remove the current crank bolt and install the ARP bolt with their Ultra-torque lubricant and re-torque to 235ft-lbs? Are there extra steps I should add to the official ARP instructions for my scenario?

http://arpinstructions.com/instructions/234-2503.pdf

RB04Av

Yes; except the confirm part is unnecessary. Once it's in the trash, won't matter what the torque on it was.

dreadpirateroberts

iTrader: (1)

the factory procedure is the proper method to achieve correct clamping force.

as muhthugga described above, the angle method is always more accurate. same reason why the head bolts are done via the angle method. just because your wrench clicks at 240 doesn't mean the required bolt stretch was achieved to produce the required clamping force (or even if you went above it). the energy from that turning force doesn't all go into clamping force, much of it is used in overcoming friction between threads. because of corrosion, differences in bolt coatings, possibility of contaminants, imperfections, there is no way to accurately control how much goes into stretching the bolt and how much is lost via other means by rotational force. it's far better to calculate how much clamping force is achieved from how much the bolt turns after it has been seated, because that amount is directly due to the energy applied to the bolt stretch and not due to frictional loss.