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jdemaris
03-09-2006 11:54:56
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Re: 4-239A DEERE engine in reply to Mike M, 03-09-2006 06:49:57
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Here is my non-scientific observation on the matter of reusing rod bolts - especially with Deere. Up to the early 1980s, we used the torque method with oiled threads. Up to that point, I don't think I ever saw a failed rod-bolt. Deere told us to measure the old bolts - and if they hadn't stretched to a certain point, then they had NOT yielded, and to reuse them. We did, no problems. Every diesel we rebuilt, standard procedure was to #1 measure the length of the rod-bolt, and #2 check the big-end of the rod for roundness and resize if necessary. Then somebody had the bright idea to come up with a new rolled-thread or extruded thread bolt with a special anti-friction coating and NOT use the standard torque method anymore since friction was to hard to predict and control, and subsequently, could give a false reading on the torque-wrench. What a mess! After that, I started seeing failed rod-bolts, very often along with hole in blocks, bent rods, broken camshafts, etc. I suspect part of the problem was confusion on what specs to use on which bolt. For me - if I'm working on an older engine with the older style rod-bolt, and it is NOT stretched, I reuse it. I haven't had one go bad yet. A newer, high-output engine - things are different and I would use whatever is recommened. One note on the new technology - my neighbors 2 year old Dodge truck with HO Cummins diesel is going in the shop for its second set of replacement, "computer-designed" head-bolts. How many head bolts have you seen fail in the older engines?
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