Broken Main Bolt. How to fix?
Thread Starter
Race Director
Joined: Apr 2003
Posts: 19,351
Likes: 654
From: Tampa, Florida
Broken Main Bolt. How to fix?
Looks like one of the outer bolts on main #2 is broken off at the block. There may be a little sticking out but if there is it isnt much (I haven't removed the cap yet). What are my options as far as fixing this?
1. Should I remove the main cap and try to remove the bolt? If I'm able to grab onto it and remove it should I replace that single bolt or all 4?
2. Considering it's a 4 bolt main block should I leave it as is? Its a relatively low HP engine that doenst get run overly hard.
Realisticly, what are my odds of getting the broken bolt out? Is there a preferred method for this type of problem?
Thanks,
Jim
1. Should I remove the main cap and try to remove the bolt? If I'm able to grab onto it and remove it should I replace that single bolt or all 4?
2. Considering it's a 4 bolt main block should I leave it as is? Its a relatively low HP engine that doenst get run overly hard.
Realisticly, what are my odds of getting the broken bolt out? Is there a preferred method for this type of problem?
Thanks,
Jim
Instructor
Joined: May 2009
Posts: 180
Likes: 1
From: Prairieville Louisiana
Use a center punch on it in the center. Get you a 1/8 drill bit and drill a hole in it. Buy you a 1/4in. LEFT hand twist drill bit, reverse drill and see if it doesnt back out. If not, use an "easy out" extractor.
Pro
Joined: Oct 2006
Posts: 734
Likes: 0
From: Bryan Texas
Yes, take the cap off.. If you can't get pliers on it, Dremel a slot in it and back it out with a screw driver. Be sure to mask things off... should come right out. I'd probably just replace the one if it's a low hp engine.
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Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
The odds of successful removal are greatly increased by following Terry's advise. Weld a nut to it, let it cool and use a six point socket to remove. The heat from the welding will help break the bond if corrosion is somehow responsible, however unlikely that seems! It would be my guess that the bolt was initially fatigued or stressed on install. If able to grab the end of the bolt it should literally spin out by hand.
Le Mans Master
Joined: Jun 2004
Posts: 6,231
Likes: 65
From: Seattle WA
St. Jude Donor '14
100% This is the approach I'd take. The question of why it broke is a good one - can you post pictures of the bolt?
Le Mans Master
Joined: Aug 2003
Posts: 7,720
Likes: 12
From: Chattanooga TN
My experience as well. Should just come right out. No way I put it all back together and just leave it as-is.
Thread Starter
Race Director
Joined: Apr 2003
Posts: 19,351
Likes: 654
From: Tampa, Florida
Thanks to evereyone who suggested ideas on how to fix it. Here's my plan:
1. Re-install rear main w/ new seal. (I'd rather not have 2 mian cpas removed at the same time.
2. Remove #2 main cap.
3. Try grab hold of broken bold and remove it. If there's nothing to grab onto:
3b. Dremel a slot in the bolt and try to remove it with a screwdriver. If that deosnt work:
3c. Weld a nut onto the broken bolt. I won a Dremel but not a welder which helps to prioritise my options.
Once I get the bolt out whould I:
1. Use 4 new bolts on the #2 main?
2. Re-use the 3 good bolts and use 1 new bolt?
3. Should I check the torque of all the bolts? This seems obvious but if I have 1 broken bolt I'd rather not break another but then again why not check the torque to rule out any that are 'on the edge'.
I'll post pics of the broken bolt later today.
Jim
1. Re-install rear main w/ new seal. (I'd rather not have 2 mian cpas removed at the same time.
2. Remove #2 main cap.
3. Try grab hold of broken bold and remove it. If there's nothing to grab onto:
3b. Dremel a slot in the bolt and try to remove it with a screwdriver. If that deosnt work:
3c. Weld a nut onto the broken bolt. I won a Dremel but not a welder which helps to prioritise my options.
Once I get the bolt out whould I:
1. Use 4 new bolts on the #2 main?
2. Re-use the 3 good bolts and use 1 new bolt?
3. Should I check the torque of all the bolts? This seems obvious but if I have 1 broken bolt I'd rather not break another but then again why not check the torque to rule out any that are 'on the edge'.
I'll post pics of the broken bolt later today.
Jim
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Measure the depth of the threaded hole for that broken bolt [once you get the shank out]. Maybe it's a shallow hole and the bolt bottomed-out but did not seat solid on the cap. I'm trying to figure out how the outer bolt could break off and the only thing that makes sense is that the bolt was overtorqued to {try to} get it fully seated. If it was a new bolt, it had to be cracked when new or cracked from overtorquing. I'm at a loss for other alternative causes.
Thread Starter
Race Director
Joined: Apr 2003
Posts: 19,351
Likes: 654
From: Tampa, Florida
When I line up the broken bolt the head seems to lineup evenly with the main cap. I'll know more tomorrow when I have chance to remove the cap
Until then, pics of bolt:
Until then, pics of bolt:
Thread Starter
Race Director
Joined: Apr 2003
Posts: 19,351
Likes: 654
From: Tampa, Florida
It was in the laying pan and yes, the break appears to be at the beginning of the threads. As I was dropping the pan I heard it rattling around and immediatly knew it wasnt going to be good.
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Assuming all comes out well, this is a great opportunity to replace all the main bolts with a good set of ARP bolts.
ARP #070-234-5201 $74
SB-Chevy, 4-Bolt, Large Journal, 12-Point Pro Series
http://www.jegs.com/i/ARP/070/234-5201/10002/-1#
Good luck... GUSTO
ARP #070-234-5201 $74
SB-Chevy, 4-Bolt, Large Journal, 12-Point Pro Series
http://www.jegs.com/i/ARP/070/234-5201/10002/-1#
Good luck... GUSTO
Melting Slicks
Joined: Dec 2006
Posts: 2,669
Likes: 3
From: Kingston Ontario
If speculating on the failure, I would bet that the bolt has been layin' around since the last bolt installation. The same surface appearance on the entire surface indicates the failure occurred at the same time (ie; complete shear). I would think that the bolt fatigued while being torqued because it either ran out of threads or because of a restriction existing in the block which is limiting the depth of bolt penetration.
Once the broken bolt is removed; with the cap removed insert a bolt into the block and confirm that the proper depth can be obtained. I would also measure the shank length of the broken bolt compared to one that is not damaged. Do the other outer bolts which are installed have individual washers? If so, and you haven't found the washer (because it wasn't installed) for your broken bolt, that thickness may have allowed the installer to run out of threads.
On a positive note; it is the right time of year to be rebuilding.
Once the broken bolt is removed; with the cap removed insert a bolt into the block and confirm that the proper depth can be obtained. I would also measure the shank length of the broken bolt compared to one that is not damaged. Do the other outer bolts which are installed have individual washers? If so, and you haven't found the washer (because it wasn't installed) for your broken bolt, that thickness may have allowed the installer to run out of threads.
On a positive note; it is the right time of year to be rebuilding.
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
UH! back up a little bit and think real hard, why not leave the maincap on and use it as a guide for getting the bolt drilled dead center. Find a bit that is slightly smaller than the bored hole in the main cap and center drill the broken bolt to get a center location, then remove the main cap and use a reverse twist drill bit to drill bolt for a screw extractor, many times the bolt will come out during the drilling process and your home free! Good Luck!