Rod bolt failure or rod failure...
08-21-2008, 12:42 PM
#1
Staging Lane
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Rod bolt failure or rod failure... Company name on the rods I'll leave out. They are a 4340 H-beam, and they use ARP 8740 bolts. I ran through the torque sequence three times.
After inital fire oil pressure fell off a little and developed a tick that was RPM related. Pulled the heads and swapped the lifters and pushrods, tick still existed. After 6000 miles the oil pressure finally went away. After engine removal there are several cracks in the side of the block and hole. The #4 rod failed. Knowing I torqued it as thoroughly as I did I was suprised to see that the threads on one side of the rod itself appear un-effected. Its almost as though it wound itself out.
Could harmonics of the part cause that or a bolt that didn't get correctly heat treated. I have my ideas, but wanted to see if anyone else here has seen a similar issue.
After inital fire oil pressure fell off a little and developed a tick that was RPM related. Pulled the heads and swapped the lifters and pushrods, tick still existed. After 6000 miles the oil pressure finally went away. After engine removal there are several cracks in the side of the block and hole. The #4 rod failed. Knowing I torqued it as thoroughly as I did I was suprised to see that the threads on one side of the rod itself appear un-effected. Its almost as though it wound itself out.
Could harmonics of the part cause that or a bolt that didn't get correctly heat treated. I have my ideas, but wanted to see if anyone else here has seen a similar issue.
08-21-2008, 03:31 PM
#2
FormerVendor
Never seen anything like that myself. 95 per cent of rods fail from that particular journal losing oil and the rod bearing spinning and then the actual big end of the rod failing after that. If the rod big end is not burned up and it failed it could have been a bolt failure then possibly but even then it is usually an assembly error as these rods that LS1 people are using are almost always 7/16 through-bolts or cap screws which are GIGANTIC overkill for a rod bolt on a small block even at 10K. If oil is lost to a rod though any rod will fail pretty fast. Also look to see which way the bearings are installed etc. for interference with the fillet.
08-21-2008, 03:45 PM
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Never seen anything like that myself. 95 per cent of rods fail from that particular journal losing oil and the rod bearing spinning and then the actual big end of the rod failing after that. If the rod big end is not burned up and it failed it could have been a bolt failure then possibly but even then it is usually an assembly error as these rods that LS1 people are using are almost always 7/16 through-bolts or cap screws which are GIGANTIC overkill for a rod bolt on a small block even at 10K. If oil is lost to a rod though any rod will fail pretty fast. Also look to see which way the bearings are installed etc. for interference with the fillet.
I know 100% that all rods were torqued to spec, and then double checked after initial pass.
