Oil clerance- is it OK?

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Oil clerance- is it OK?

Post  tomcat1 on October 19th 2012, 5:18 am

I am puting together my stroker with Boss heads. Crank is new Scat forged. I have foud that mains diameter on crank is 0,01 mm lower and mains bore on block is 0,02 mm biger than it should be. Everythig is perfect round and all diameters are the same. Considering that i have bought standart size set of main bearings http://www.summitracing.com/parts/SLP-134M
Oil clerance with these beraings measured with dial gauge is 0,075 mm at Y-axis and 0,12 mm at X-axis on berarings 1-2-4-5. But number 3 (axial bearing) have biger clerance- 0.095 mm at Y-axis and 0,14 at X-axis.
Is it OK?
Previosly i have try to use 0,001 inch oversized beraings same brand http://www.summitracing.com/parts/SLP-134M1X/ and with these bearings number 3 bearing clerance was also 0,02 mm biger than others...

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Re: Oil clerance- is it OK?

Post  jc10000rpm on October 19th 2012, 6:11 am

what is your target oil clearance ??
what is the intended application ??
what volume oil pump are u running ??
what weight oil are u intending to run??

if using a lighter oil i would mock it up with the .001 oversized bearings and see where i was at. using the figures given stock bearings should have u with .0008 extra clearance, not necessarily a bad thing depending on rest of setup

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Re: Oil clerance- is it OK?

Post  dfree383 on October 19th 2012, 6:41 am

Most guys here are not used to metric measurements please do everything in imperial..
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Re: Oil clerance- is it OK?

Post  bosshoss on October 19th 2012, 8:47 am

My calculation puts .075mm at .0029 inches and .095mm at .0037 inches.

Assuming you mean the vertical clearance when you say Y axis then these numbers seem just fine.

The X axis number should always be higher due to bearing design.

Use a good oil pump and good quality oil you will be golden.

dkp
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Re: Oil clerance- is it OK?

Post  tomcat1 on October 19th 2012, 10:42 am

It is engine for 600 HP street Mustang.
I am using Valvoline Racing 10W60 oil and high volume pump.
My target oil clerance is 0.0030 inch = 0,076 mm
Sorry for metric numbers...
Yes Y-axis i mean vertical dimmension.
My main question is if it is normal that nuber 3 bearing is different fom others and if the 0,0037 inch clerance is not too big...

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Re: Oil clerance- is it OK?

Post  richter69 on October 19th 2012, 11:45 am

id rather it bias to the big side over the small myself......................run it.
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Re: Oil clerance- is it OK?

Post  bosshoss on October 19th 2012, 12:23 pm

Yes I have seen the number 3 thrust bearing have slightly more clearance than others on a couple of builds. No ill effects seen.

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Re: Oil clerance- is it OK?

Post  Lem Evans on October 19th 2012, 12:55 pm

A little more clearance at the thrust bearing can be a good thing.

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Re: Oil clerance- is it OK?

Post  tomcat1 on October 19th 2012, 1:13 pm

Ok, thank you for ensure that 0.0037 is not too much. I also have oversized bearing set http://www.summitracing.com/parts/SLP-134M1X/ Do you think that it is good idea to use one halves of bearings from that set to adjust oil clerance on bearigs 1-2-4-5 the same as it is on nuber 3?
I also have question about rod bearing oil clerance- Is it 0.0016- 0.0020 too thin for my engine?

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Re: Oil clerance- is it OK?

Post  rmcomprandy on October 19th 2012, 3:30 pm

Some people like wide clearances to avoid any metal to metal contact under stressed circumstances ... the bearing manufacturers will advise against it if everything else is right.

You're call ... as nobody else will know for sure exactly what conditions are there.

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Re: Oil clerance- is it OK?

Post  dfree383 on October 20th 2012, 12:00 am

IMO .0037 is a little much for a street engine. high but OK on the thrust but I wouldn't losen the other mains up to that spec.

I like .0025-.0028 ish on the rods and around .003 on the mains.

Big HP race stuff is OK with the looser clearances.
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Re: Oil clerance- is it OK?

Post  LivermoreDave on October 20th 2012, 10:44 am

A "workable" rule of thumb is .001" of oil clearance per 1.0" of journal diameter. As previously mentioned, the center main of a Ford 385 series engine usually has a bit more oil clearance unless the area has been manipulated otherwise. It requires a bit of leakage to supply oil to the thrust surfaces of the bearing, although most thrust bearings are manufactured with a route for the oil to flow in the thrust area direction. As to the .0037" of oil clearance at the number 3 main location and considering this is a street application, although not my preference, it will be just fine.

Just my $0.02,
Dave.

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