If your big end bores are oversize then you won't get the correct clamping pressure to hold the bearings in place which will more than likely lead to a spun bearing. Get them resized correctly
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| Big end bearing clearence https://www.ausmini.com/forums/viewtopic.php?f=2&t=89685 |
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| Author: | Ian_B [ Wed Jun 10, 2015 9:26 pm ] |
| Post subject: | Big end bearing clearence |
Is two and a half thou too much.Crank is standard . |
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| Author: | Ian_B [ Wed Jun 10, 2015 9:41 pm ] |
| Post subject: | Re: Big end bearing clearence |
Are plus one thou bearings available?? Its outside limits |
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| Author: | ba_dm_tsh [ Thu Jun 11, 2015 4:23 am ] |
| Post subject: | Re: Big end bearing clearence |
Two and a half thou clearance is still just within tolerance. If you want to get closer to the minimum tolerance of one thou then you will need to have the crank ground and run +10 thou bearings. I would suggest obtaining the bearings first. Have you checked that your big ends are still round? It may be the rods that are out of size... How have you checked your clearance? |
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| Author: | drmini in aust [ Thu Jun 11, 2015 8:26 am ] |
| Post subject: | Re: Big end bearing clearence |
re the crankpin roundness, any more than .0005" (1/2 a thou) ovality and it really should be reground. I have seen low mileage 1275 cranks with .007" ovality there due to oil starvation on roundabouts etc. IMO fitting a centre oil pickup is a bloody good idea. [edit] I would rather have .001" extra clearance than .001" ovality. Ovality mucks up the oil film. |
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| Author: | Ian_B [ Thu Jun 11, 2015 8:42 am ] |
| Post subject: | Re: Big end bearing clearence |
Thanks guys .The crank isn't the issue .Its fresh offset ground. The aftermarket H beam rods are half thou oversize in the bore Not sure if I need them closed and honed.grr |
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| Author: | ba_dm_tsh [ Thu Jun 11, 2015 7:53 pm ] |
| Post subject: | Re: Big end bearing clearence |
If your big end bores are oversize then you won't get the correct clamping pressure to hold the bearings in place which will more than likely lead to a spun bearing. Get them resized correctly
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| Author: | drmini in aust [ Thu Jun 11, 2015 8:05 pm ] |
| Post subject: | Re: Big end bearing clearence |
ba_dm_tsh wrote: If your big end bores are oversize then you won't get the correct clamping pressure to hold the bearings in place which will more than likely lead to a spun bearing. Get them resized correctly Last time, I got a set done by St George Cranks in Seven Hills, Spiro does nice work. I supplied him the ARP rod bolts. |
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