Rod Bearings

Old 04-07-02, 09:51 AM
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Question Rod Bearings

Sorry about not posting results for my 78 F-250. I took the timing cover off, evrything looked fine. Put it all back together, and it started. I missed something along the way, apparently, and fixed it by accident. But I digress...

I put new rod bearings into the engine while I had it part, because they were rattling at high speeds (60-70mph). When I took the old ones out, WOW were they on tight!!!! I put the torque wrench to the new ones, and put them to Chilton specs. Now that the truck is running, they seem to rattle at the slightest raising of the throttle. Could the old bearings have been on SO tight that they damaged the crank? Or did I mess something else up?

Oh, in case y'all forgot, it's a 1978 F250, with a 400(6.6l).
I put new timing set, rod bearings, oil pump, and lifters into the motor. As well as valve guides/seals, and a couple of new valves.
Old 04-07-02, 10:22 AM
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The crank itself wears.You need to mic the new bearings to make sure they're in spec.If not you may need oversize bearings.Any auto parts store carries the mic material.It looks like a thin string of wax.Different colors denote different thousandths of an inch.
Old 04-07-02, 06:22 PM
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The crank may also be bad as a result. Might be worth having a machine shop go through it all for you.
Old 04-08-02, 07:04 PM
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Rod bearings

You didn't tighten the bearings. you only tightened the cap to the rod. The standard bearings were still too loose. I suggest shim stock under the bearing (try .010 or .020 ) and with cap tight feel for slight side way movement that is rather difficult to make. You can get the feel pretty easily.Usually, the crank wears pretty evenly. It will give you another year at least.
Old 04-08-02, 07:20 PM
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I wouldn't trust any shimming materials.
The best way as I said would be to mic and replace with an oversize bearing to your spec.And if you havn't spun a bearing resurfacing the crank may not be neccessary.
Myself personally I don't like replacing bearings on high mileage cars.I would rather take the motor out and rebuild from the ground up.

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