Why get a new harmonic balancer/crank bolt?
Why get a new harmonic balancer/crank bolt? Just curious why I've searched and found you guys suggesting getting a new crank bolt when putting a different harmonic balancer on?? Someone said the stock bolt gets stretched under torque, and others said it could try to back out. What causes that or how can I tell if I can or cannot use the same bolt?? Trying to convince my dad why everyone on ls1tech suggests it, since he recently re-used one of these bolts on a Chrysler v6 and hasn't had any problems with 10,000 miles since. Might as well ask this since the topic is convenient, Any tips on putting the harmonic balancer & bolt in? What size socket do I need for the bolt?? Where can I get the cheapest bolt? Lowes/hardware store, automotive supplies shop, dealer??
Thanks to everyone!
Thanks to everyone!
TECH Resident
Joined: Jan 2003
Posts: 937
Likes: 0
From: South Alabama
On this car (have no idea about yer crysler) this bolt is torque to yield. The bolt is purposely torqued into the plastic range of deformation. For a ONE TIME DEAL ONLY it causes the bolt to provide a higher clamping force under the head. Like I said its a one time deal only, if used again it will torque even further into the plastic deformation range of elasticity making the bolt now weaker than it was to begin with (prior to the first "torque to yield" process). The bolt is more apt to fail at this point, thats why its recommended to use a new bolt.
Most bolts stretch, and there is a range of up to 2% elasticity that allows no permanent damage (no permanent deformation) to a bolt, it will stretch and return to its original condition and length. You can literally use a bolt this way thousands of times with no problems; however, take it just one time past this point and into the permanent range of deformation (known as plastic deformation) and you’ve deformed the bolt – stretched it so far it cannot return to its pre-stressed state.
Hence the need for a replacement.
Most bolts stretch, and there is a range of up to 2% elasticity that allows no permanent damage (no permanent deformation) to a bolt, it will stretch and return to its original condition and length. You can literally use a bolt this way thousands of times with no problems; however, take it just one time past this point and into the permanent range of deformation (known as plastic deformation) and you’ve deformed the bolt – stretched it so far it cannot return to its pre-stressed state.
Hence the need for a replacement.
Last edited by Weezzer; May 27, 2008 at 05:50 PM.
Any GM dealer should have them, I picked up mine at the chevy dealership close to home, $12.00 a few years ago. I had a buddy w/ a lift and impact wrench install my ASP pully took 10 minutes. Make sure you get the New Bolt on tight, another local ls1 f-body guy had one come off while driving, did some damage when pully flew out under the car.
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Weeezzer forgot part of it... do it this way...Use your old crank bolt and torque it to 240 pounds. Take the old crank bolt out and torque the new crank bolt to 37 pounds.....now get the longest piece of pipe you can find and put it over your breaker bar and turn it 140 degrees and you will have installed your crank pulley correctly...
..If you go to LS1howto.com or installuniversity.com you will find a lot of good info to help you with different mods to your LS series engine and there are photos too.
..If you go to LS1howto.com or installuniversity.com you will find a lot of good info to help you with different mods to your LS series engine and there are photos too. 
What tool do you use to pull the balancer off? Can a gear puller be used, or do you need to use a special balancer puller for the LS1? When putting the new balancer on, do you use the balancer installation tool, or just the old bolt?
