Broken flywheel bolt - I got extremely lucky.
Thread Starter
Track Junky
Joined: Jun 2007
Posts: 4,075
Likes: 36
From: Orlando Area
Tech Contributor
Broken flywheel bolt - I got extremely lucky.
Has anybody ever broken a flywheel bolt before reaching final torque (74 ft-lbs)? I was making my third pass from 37 ft-lbs to 74 ft-lbs and one bolt just wouldn't click. I turned it about a quarter to a half turn further than the others and it suddenly got "soft". I was extremaly lucky to be able to back it out without it snapping off in the crank... Bolt is visibly damaged in 2 places a few threads under the head. Crank threads appear to be entact. A different bolt threaded in with no issue.
These were brand new GM flywheel bolts! I went very slow and did it by the book. I've never heard of a 10.9 bolt shearing prior to reaching rated torque. Any of you have history with this?
This was my first (and last) time I have done a performance upgrade with GM replacement bolts - ARP only from now on. I guess I got a bad batch of bolts. They almost cost me a motor!
Others may want to take this into consideration when choosing between GM replacement and ARP bolts.
These were brand new GM flywheel bolts! I went very slow and did it by the book. I've never heard of a 10.9 bolt shearing prior to reaching rated torque. Any of you have history with this?
This was my first (and last) time I have done a performance upgrade with GM replacement bolts - ARP only from now on. I guess I got a bad batch of bolts. They almost cost me a motor!
Others may want to take this into consideration when choosing between GM replacement and ARP bolts.
Thread Starter
Track Junky
Joined: Jun 2007
Posts: 4,075
Likes: 36
From: Orlando Area
Tech Contributor
Race Director
Joined: Dec 2005
Posts: 11,910
Likes: 107
From: God's Country, ID
I just R&R'd my heads n cam and replaced all fasteners avail with ARP. Well worth the $$ IMHO.
The newer cam retainer plates require a tapered bolt....(not sure if ARP carries those?) I found hardened tappered bolts at a hardware store that fit the recessed holes in the retainer plate perfectly. Chevy dealer wanted to take 7 days to drop ship them directly from the manufacturer.
I try to use aftermarket parts, fasteners etc whenever available. GM quality has further decline to save $$ IMHO.
The newer cam retainer plates require a tapered bolt....(not sure if ARP carries those?) I found hardened tappered bolts at a hardware store that fit the recessed holes in the retainer plate perfectly. Chevy dealer wanted to take 7 days to drop ship them directly from the manufacturer.
I try to use aftermarket parts, fasteners etc whenever available. GM quality has further decline to save $$ IMHO.
Melting Slicks
Joined: Mar 2008
Posts: 2,835
Likes: 5
From: Avon Park FLORIDA
St. Jude Donor '08-'09-'10
I just R&R'd my heads n cam and replaced all fasteners avail with ARP. Well worth the $$ IMHO.
The newer cam retainer plates require a tapered bolt....(not sure if ARP carries those?) I found hardened tappered bolts at a hardware store that fit the recessed holes in the retainer plate perfectly. Chevy dealer wanted to take 7 days to drop ship them directly from the manufacturer.
I try to use aftermarket parts, fasteners etc whenever available. GM quality has further decline to save $$ IMHO.
The newer cam retainer plates require a tapered bolt....(not sure if ARP carries those?) I found hardened tappered bolts at a hardware store that fit the recessed holes in the retainer plate perfectly. Chevy dealer wanted to take 7 days to drop ship them directly from the manufacturer.
I try to use aftermarket parts, fasteners etc whenever available. GM quality has further decline to save $$ IMHO.
ARP
Thread Starter
Track Junky
Joined: Jun 2007
Posts: 4,075
Likes: 36
From: Orlando Area
Tech Contributor
Yeah, I gotta hand it to ARP. I haven't heard of any issued with their product. On the other hand, in all my time under the hood, I have never seen a grade 10.9 bolt begin to spin the head off it prior to reaching torque. Those bolts aren't supposed to break. They have a minimum tensile strength of 150,000 psi.
Like I said before, I'm lucky to get it out ion one piece. It saved me from removing the block. I'm not pleased with the quality of the GM bolts I paid for.
Sean
Like I said before, I'm lucky to get it out ion one piece. It saved me from removing the block. I'm not pleased with the quality of the GM bolts I paid for.
Sean
Melting Slicks
Joined: Feb 2004
Posts: 3,307
Likes: 111
From: Tucson AZ
Sean,
Yes, I have had several bad Chevy bolts. Usually they were head bolts, but several years ago I even had a bad batch of boron rod bolts for an L88. They would just stretch and would not take the final torque.
ARP is much better quality. Just note that you must use the specified lube (oil, ARP bolt lube, or Locktite) or the torque is not accurate.
Yes, I have had several bad Chevy bolts. Usually they were head bolts, but several years ago I even had a bad batch of boron rod bolts for an L88. They would just stretch and would not take the final torque.
ARP is much better quality. Just note that you must use the specified lube (oil, ARP bolt lube, or Locktite) or the torque is not accurate.
Thread Starter
Track Junky
Joined: Jun 2007
Posts: 4,075
Likes: 36
From: Orlando Area
Tech Contributor
Vito, thanks for the reply. This was the first and last time I will ever use GM replacement bolts for car repairs. I have ARP crank and head bolts with great success. The new ARP flywheel and pressure plate bolts will be in tomorrow so I can finally get this car back together and back on the dyno.
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Burning Brakes
Joined: Jul 2008
Posts: 923
Likes: 37
From: Green Bay Wisconsin
Hello,
A few questions:
Did you make sure the bolt was clean and dry before install?
Have you checked the calibration of your torque wrench against another torque wrench?
Something not right about breaking these bolts.
Douglas in Green Bay
A few questions:
Did you make sure the bolt was clean and dry before install?
Have you checked the calibration of your torque wrench against another torque wrench?
Something not right about breaking these bolts.
Douglas in Green Bay
Thread Starter
Track Junky
Joined: Jun 2007
Posts: 4,075
Likes: 36
From: Orlando Area
Tech Contributor
Bolt was clean, straight out of the box. Torque wrench was not checked. Haven't had a problem with it up to now, but you are correct in that it could be out of cal. This one particular bolt felt different from the rest during the final pass though. That's why I'm leaning towards a bad bolt.
After some brief research, it appears that others have had issues with sheared or broken GM replacement bolts as well.
Melting Slicks
Joined: Mar 2008
Posts: 2,835
Likes: 5
From: Avon Park FLORIDA
St. Jude Donor '08-'09-'10
Doug,
Bolt was clean, straight out of the box. Torque wrench was not checked. Haven't had a problem with it up to now, but you are correct in that it could be out of cal. This one particular bolt felt different from the rest during the final pass though. That's why I'm leaning towards a bad bolt.
After some brief research, it appears that others have had issues with sheared or broken GM replacement bolts as well.
Bolt was clean, straight out of the box. Torque wrench was not checked. Haven't had a problem with it up to now, but you are correct in that it could be out of cal. This one particular bolt felt different from the rest during the final pass though. That's why I'm leaning towards a bad bolt.
After some brief research, it appears that others have had issues with sheared or broken GM replacement bolts as well.
My Torque wrenches get calibrated every 6 months due to FAA regs.
Thread Starter
Track Junky
Joined: Jun 2007
Posts: 4,075
Likes: 36
From: Orlando Area
Tech Contributor
I also think the ergonomics helped me. I was on my back trying to torque with the wrench over my head, so I had no choice but to go slow. I could only get 1 or 2 clicks before repositioning. I go slow for anything requiring a specific torque, especially if it means significant rework if I do it wrong.
Over the years I have kept some of my "mistakes" (spindle nuts, bearings, and now this flywheel bolt) to remind me how much $ I have or could have cost myself for not being careful. So far, the collection is small... Knock on wood!
