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Mains and Big end bearing clearances. Loose or tight 

 

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 Post subject: Mains and Big end bearing clearances. Loose or tight
Posted: Wed Jul 18, 2007 2:05 am 
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I normally leave my engine machinist (Southside engine centre) to choose the clearances.

But still interested to know what clearances people like to run on their mains and bigends.
I think stock clearances are .0025thou bigends and .003thou mains. Should I go tighter or looser for a high performance 700rwhp capable engine

 

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Posted: Fri Jul 27, 2007 12:31 am 
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Im running 3thou all the way down the crank on my supercharged clevo stroker. Will post how it goes when it hits the dyno.

These guys go into it in a bit of detail.

http://speedtalk.com/forum/viewtopic.ph ... sc&start=0

 

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Posted: Fri Jul 27, 2007 1:27 am 
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Thanks for that info. I spoke to my machinist (Graham at Southside engine centre) and he said he would do it about 3 thou on both. Basically he reckons whenever he does them at this clearance engine never comes back.

I also read a number of performance books where 3 to 3.5 thou is the clearance to aim for in a performance mtr.

 

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Posted: Fri Jul 27, 2007 3:05 am 
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thats interesting, the subaru factory spec is .0015.. i rebuilt one and did them to this clearance.. maybe that explains now why the thing spun a big end bearing (before the rebuild).... it was a my99 sti

my 4l runs .0025 clearance, cant say ive got 600rwhp, but i can say that so far, no bearing problems

 

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