Rod Bearing Question


Old 06-09-06, 02:46 AM
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Rod Bearing Question

I have a new crankshaft that came with matched bearings. I had the rods checked and reconditioned. OK, Now are my bearings still going to fit properly? Never thought to ask at shop.
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Old 06-09-06, 04:31 AM
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if you had the rods resized you should be ok. but never assume your clearances are correct. you should assemble the rotating assembly using plastigauge to check each bearing in the crank and rod journals. if you're good with a mic that will also work. assemble the caps with bearings, torque to spec and measure. consult a shop manual for the correct clearances.
Old 06-15-06, 03:15 AM
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Angry Loose Bearings

I assembled one and checked clearance, got .003. Ok, but the rod twists a tiny bit on the crank, I don't mean slides sideways, I mean it will literally twist a tiny amount. Should I increase the bearing size?
Old 06-15-06, 03:28 AM
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how did you check the clearance if it was with a mic suggest you check it with plastiguage as you need to be real familiar with using a mic to get accurate readings.
Old 06-15-06, 06:27 PM
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I did use plastigauge to check it. I am going to take the rods and have them inside mic'd on the bottom to see what's up. Perhaps a larger oversize bearing would be in order depending on the measurements?
Old 06-15-06, 06:36 PM
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Depends what you mean by reconditioned rods (just cleaned, hot tanked, bored, honed/machined, when they go to a machine shop which I am assuming they did, those guys are the only ones that can advise you). but I would call the place that did it and ask since they know exactly what they did to them and if they used a micrometer to check them to spec.

Its kinda like when people say I have such and such stage performance kit on my car. Its like ok there is no definition of stage 1,2,3 the stage is determined by the person that sold the kit with what they felt like throwing in it.
Old 06-15-06, 07:18 PM
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While I agree with scalar to the point of what was actually done is a somewhat undefined term by stating they were recconditioned. I would generally consider a rod that had the mating surfaces ground then the bore reground to size a usual part of the term "reconditioned" but it is not an absolute as scalar stated.

Now with that said, there is no neccessity to ask the shop what they did just to check clearances. While a micrometer used correctly (need both inside and outside mic's) is the most accurate, plastigage is very dependable when used corectly as well.

Since the rod bearings to journal is not a tight fit, there will be some amount of "rocking" if you tip the rod end back and forth. This is norml and meaningless by itself. The only way to know for sure if the clearances are correct is to measure them.
Old 06-15-06, 08:23 PM
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I just want to point out because it was not clear why I wanted to contact the place that worked on the rods. When I work on cars I keep a log book and as in practice of keeping a log book/CYA book its always good to know the reason for which you need oversized bearings. Is it because the rods were bored or is it because the crank isn't perfect. It was mainly a matter of habit of paper trailing the work. As you have stated from this thread my log book entry would read customer vehicle getting new crank installed with out machining and honing block. Unknown what was performed on the rods, clearances not correct when checked (clearance stated), over sized bearings installed new clearances and torqued to. I would also mic the crank and inside of rods. This way if stuff hit the roof later down the road I would say here it is in writing what was performed back them signed and dated at the bottom of the last sentence.

I always do it for things that get work outsourced and then I have to put it back together. Its a matter of every one always says their work is perfect and its always the person that put it together that screwed up. I have had friends that got burned for jobs that I watched them do correct but the part failed. So I thats why I always try to trace papers/work as much as possible.

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