Machinist ? need help

[Blown R1]

I have done alot of motor rebuilds, i have recently done my bosses 93 chevy 1/2 ton 350, it was knocking he only wanted to do the lower end so i did, the machine shop went 10 on the rods and 30 on the mains i put it together by torque specs like always. i think it lasted 20 miles before it thru a rod. my concern was we took the pan off and some off the rod cap bolts were loose and one of the machine shops asked if the rods were oblonged could this have caused me to torque the caps down then been run in the motor and heat and made the caps stretch or relax and make the rod cap nuts loosen up....?

[jkinney]

Rods will oblong after so long of service. They do need to be "resized" if they have too many miles on them, and/or they have had a bearing spun on them. What torque specs did you put them to, and how many miles did the motor have on it when you took it apart. If the damage the engine received (originally) was a result of high heat (lack of oil, or coolant) it is recommended you machine the crank, resize the rod ends, and use new connecting bolts. I have done what you've explained, but only when the miles were fairly high, and the oil consumption was still real low, and the engine was still clean. Also, If the old bearings were wearing fairly smooth and uniform, you can still change only the bearings to get a better clearance back and help the oil pressure. Did you try to clean the crank up at all?, and if so how?