Engine oil clearance

Off Topic
#1

I have the motor in the truck,4.3 chevy rebuilt,and used 1 thousands under sized bearins,with out checking with plastigauge,in the first place.I have 1.25 thousance on one main bearing,the rest of the rods and mains are 1.5 too 2 thousands clearance, I read at arc raceing oil clearance that if your clearances are in the tight range 1.5 thousans,then run thin oil and if your engine oil clearance is in the loose range 3.5 thousands then run thick oil. thick oil wont work with tighter clearances. ARE THERE ANY GEAR HEADS OUT HERE THAT HAVE THE FACTORY SPEC ON OIL CLEARANCE 4.3 chevy engines,rods and mains.1991 astro THANKS

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#2

This probably isnt much help but I would probably just put a mechano gauge on there and check the pressure with standard 10-30 you can do this by filling it and cranking the pump with a drill.

#3

Hello Kevin
.001 to .002 is about the norm for those engines, but when you have clearances that small you want to be sure the rod journal , main bearing journal & main bearing line bore are with in spec. ( meaning rod & mains are perfectly round and mains are in perfect alignment).
I am sure the oil recommended by the manufacture would be just fine ( up here we would use 5-30 weight).
Calvin…

#4

Hi joseph H, I do use the drill too prime the oil pump and plan on useing reg mechanicle gauge, I would have new standard bearings in had the car parts wizard on ebay not sent me the wrong bearings. Thanks

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#5

Hi calvin radar, Well i have a few mains at .001 not counting the oil behind the bottom bearing, The rods are .015 too .002, like you say it may be a little tight on the mains, i gess for raceing motors they like at least .002 too .003 .so since i aint pushing 8 or 9 grand RPMs, it should be good with the thiner oil,THANKS. PS how is that wood gas camper doing on MPG.

#6

I put on a 100 miles so far, in the last 75 persent, found a couple vacuum hoses blown of that I mist from last back fires I had . So I had to reseal the air cleaner lid again.
It blew the air cleaner lid up so hard it dented the hood.
Of course you know what the air cleaner lid would have looked like after that happened.
Any way we will win…Calvin…

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#7

Thanks calvin R, Glad your getting it mastered,i am soon too join the 75 percent learning club, And dam i wish them tellimarketers would stop ? calling/damed illegle’s/ .HOPEING too have burning wood gas next week.
THANKS SWEM>

#8

I heard that the best way too use the .001 or the .002 over sized bearings are use one half only, in order too keep all oil clearances all the same as posible./

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