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Plastiguage on main bearings opinion
Topic Started: May 15 2011, 08:59 PM (1,111 Views)
mkc1962
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86 G10 3cyl

Ive heard several here say that when they do an entire rebuild they often just reuse the mains IF they physically look good. Well my mains looked good but I've decided to replace them anyway. However, both the old and the new std mains, plastiguaging shows the oil gap to be way out of spec at .076mm. Max limit according to my chevy tech manual shows the max to be at .060mm, with a useable range of .020-.040 mm.

Has anyone ever taken the time to actually check the limit, or do the masses just go with what looks good? I'm thinking an excessive oil gap would account for lower than avg oil pressures.
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starscream5000
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Got 70 MPG?

You need oversized bearings, don't use the std. sized ones with a gap that large. Your oil pressure is going to be nearly zero.

My unopened motor with over 210K miles on it has about 22psi oil pressure at hot idle (oil temperature at or above 200 degrees) and to me that is almost too low for comfort. I'm used to my GTP with 102K miles having 54psi at hot idle.
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mkc1962
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Thanks for the feedback....the answer I wanted to hear and what I figured would be the proper choice....If I have it figured proper, the #2 oversize should put me back into the mid .020's mm range
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Coche Blanco
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Where are you from in Alabama?
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wizard93
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Check the bearing clearance with one of the old bearings and see what you get. On the back of the bearing, sometimes there's a number stamped into it if it's an oversize (or undersize, however you wanna say it) bearing, like .010, .020 or something like that.
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mkc1962
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I mic'd all old vs new all were the same, but also checked the old ones with Plastiguage. Plasti on old or new both showed the same clearance.

The old ones did have markings, but more like a part number vs a size.

Old were the original factory. Rebuilding at 154k.


COCHE,

Valley Grande (North Selma)
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Coche Blanco
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Ah about 3.5 hours from me. Have fun with your rebuild!
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mkc1962
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And where would you be in alabama?

Yeah this rebuid been going on about 2 months now in free time...
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Coche Blanco
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Huntsville/Madison/Hartselle, just depends on my mood.
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