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Engine Noise at 3000 rpm after rebuild


squidberg

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Thats a big ass clunk,I would be leaning towards your rod knock theory. Clearance there is way, way smaller than that.

Standard size bearing shells installed on a reground big end journal?

Sorry for your trouble but open it up! We want to see, and help

Edited by tech71

76 2002 Survivor

71 2002 Franzi

85 318i  Doris

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8 hours ago, tech71 said:

Thats a big ass clunk,I would be leaning towards your rod knock theory. Clearance there is way, way smaller than that.

Standard size bearing shells installed on a reground big end journal?

Sorry for your trouble but open it up! We want to see, and help

#2 has a faint groove. Hopefully it’ll polish out. Rest were smooth. 

 

5 hours ago, Hans said:

And you had it running like that???

250 miles. 

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The reason I said take to engine builder is for that very reason, I had a motor that was supposedly rebuilt when I put my car together but since I didn't put motor together I didn't trust it. I took my motor to builder (friend) to double check everything and he found same problem as yours. Previous rebuild used standard main bearings on a .010 ground crankshaft. 

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23 hours ago, squidberg said:

The rod journals were .25 under as measured. So I put in bearings that were .25 over. A trained machinist would have known there was still something wrong. I'm learning...

 

Over, under... i don't get it. Where do you get rod bearings in oversize?

Racing is Life - everything before and after is just waiting!

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1 hour ago, Tommy said:

Over, under... i don't get it. Where do you get rod bearings in oversize?

Pretty much anywhere, a crankshaft ground undersize (to clean up wear, damage out of round) would require a thicker (oversize) bearing to make up the difference. The bearing is a 2 piece shell, 1 piece fits in the block and the other in the cap.  So, undersize crank requires oversize bearing. The bearing size is always marked on the back side of the bearing shell. 

Its common engine overhaul stuff, you measure stuff with a micrometer and compare to the published data/specs. Its not quantum physics but does  require some reading, measuring, basic math and proper assembly .

These are on Amazon, they are .010 oversize.

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Edited by tech71

76 2002 Survivor

71 2002 Franzi

85 318i  Doris

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58 minutes ago, tech71 said:

Pretty much anywhere, a crankshaft ground undersize (to clean up wear, damage out of round) would require a thicker (oversize) bearing to make up the difference. The bearing is a 2 piece shell, 1 piece fits in the block and the other in the cap.  So, undersize crank requires oversize bearing. The bearing size is always marked on the back side of the bearing shell. 

Its common engine overhaul stuff, you measure stuff with a micrometer and compare to the published data/specs. Its not quantum physics but does  require some reading, measuring and proper assembly .

These are on Amazon, they are .010 oversize.

 

 

 

 

Ok maybe I have an issue with translation, I thought the bearing is called undersized according to ground journal. I guess I was wrong. I'm pretty sure that's how it is in finnish - tzei help me? I have only used std sized bearings in my builds.

Edited by Tommy

Racing is Life - everything before and after is just waiting!

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 I am being too literal, sorry. Forget I said "oversize" In this case, a poor choice of words.

A bearing shell marked on the back .010(in) or .25(mm) is for a crankshaft that has been ground down to the 1st regrind diameter and fits an undersize crankshaft. 

Edited by tech71
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76 2002 Survivor

71 2002 Franzi

85 318i  Doris

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  • 3 weeks later...
8 hours ago, Hans said:

So you got that sucker apart yet?

Yes. I have ordered new pistons and once they’re made and in the shop they will bore the cylinders to match. Somehow the crank seems to only need a polish. New pistons will be 90mm bathtubs with 9.6:1 compression ratio from JE. 

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