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| How much is too much https://www.ausmini.com/forums/viewtopic.php?f=2&t=74945 |
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| Author: | Beanie [ Wed Jan 11, 2012 11:16 am ] |
| Post subject: | How much is too much |
Ok so i need to get a crank ground ... its currently on -20 on the mains and -20 on the big ends .. sooooo my question is how far can you safely take a crank that is going to be abbused ( 8000 rpm ) im hoping my damage will clean up at another 10 tho ( i ran the engine with low oil and the preassure dropped ) the crank in question is a cooper s crank.. Thanks Beanie |
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| Author: | drmini in aust [ Wed Jan 11, 2012 12:23 pm ] |
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My spare 20/20 EN40B S crank suffered the same fate on a track day, and just cleaned up at -.030" on the mains. Failure was due to insufficient crank endfloat (.003")- I've learned my lesson, I now run .007" on both my 1275 cranks. IMO the size & quality of the corner fillet radii is more important than the undersize, if you are going to rev it.... 
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| Author: | TheMiniMan [ Wed Jan 11, 2012 12:39 pm ] |
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well,,, i expect quite a few you will be ready for this one  But anyways-->
i`ve been running .080 under big-ends in my 1510cc engine & it`s done about 8 or 9 years of mostly 7800rpms
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| Author: | GT mowog [ Wed Jan 11, 2012 12:41 pm ] |
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The factory only recommend -0.020" on the Mains and -0.040" on the Big Ends. Now, this is what the factory say. You can take both of them down to -0.040" on each and bearings are fairly readily available, but it is outside factory recommendations. I ran one at -0.040 on both for ages, but I didn't try to kill it either. Plenty of people have taken them small than even this and Most of the time you can get away with it. Bigger is usually better though. |
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| Author: | Beanie [ Wed Jan 11, 2012 12:52 pm ] |
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Ok thanks ... Have just spoken to the Machinest and the crank has a 6 tho run out in it ... they hope it will clean up with going -10 under and 2tho clearance .. Here's hoping that that works .. if not got a new crank to buy 
all this because the rocker cover gasket failed ... i mannaged to pump 3 litres of oil out of the rocker cover in 8 laps .. 
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| Author: | TheMiniMan [ Wed Jan 11, 2012 1:04 pm ] |
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Beanie wrote: all this because the rocker cover gasket failed ...
No offence but--> looks more like the person who fitted the rocker cover gasket failed
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| Author: | Beanie [ Wed Jan 11, 2012 1:07 pm ] |
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TheMiniMan wrote: Beanie wrote: all this because the rocker cover gasket failed ... No offence but--> looks more like the person who fitted the rocker cover gasket failed No offence taken ... quite correct I stuffed up |
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| Author: | Morris 1100 [ Wed Jan 11, 2012 1:09 pm ] |
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TheMiniMan wrote: Beanie wrote: all this because the rocker cover gasket failed ... No offence but--> looks more like the person who fitted the rocker cover gasket failed 
That is why I glue the gasket to the rocker cover with contact adhesive and use non-hardening sealer on the other face. Was the motor running some sort of vacuum breather system? |
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| Author: | Beanie [ Wed Jan 11, 2012 1:33 pm ] |
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yeah will be glueing the gasket from now on .. there was no vac system just a breather tank ... and that was empty .. the only thing that i suspect is that the cam bearing was put in the wrong way which would pump too much oil to the head .. Not a problem unless the gasket doesnt seal .. Beanie |
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