View Full Version : what size bearings?
01-28-2012, 12:31 PM
Im wanting to do my 1st backyard engine rebuild. Im honestly not that blessed with mathematics. I Purchased a micrometer and plastigauge. from watching videos etc on youtube say the plasti reads 15 thousands clearance.. Does that mean i need .15 bearings? This is a budget build. I got the engine (5.7 tbi) for free. Seems to turn over,not sure if it runs. Unknown mileage.
01-28-2012, 12:50 PM
plastigauge can only be used if the crank and bearings are free of oil. it is available in varying ranges of thickness, color coded. place it across the crank journal and install the rod/or main cap and torque to spec. Remove the cap and the plastic will be flattened to a certain width. Compare it to the chart on the plastic package. Should not be .015 on any auto bearing. more like .0015-.002 but you will need info specific to your engine.
01-29-2012, 06:12 PM
Green plasti-gauge is the right stuff for cranks. It's something like .001-.003 thousandths, which I was told are the guidelines for oil clearance on the main and rod bearings.
The oversize bearings are for when you get a crankshaft ground undersize. You can get a crank ground .010 under if it's got some scoring, then you need .010 oversize bearings to make up for the smaller journals. When I did my rebuild, I just purchased a crankshaft kit from Oriellys. You give them your crank, pay 100.00, and they give you a ground/polished crank with matching main/rod bearings. My crank was not damaged but because I don't have a local machine shop, my motor had OEM bearings in various sizes, and because the nearest place wants 60.00 to grind/polish a V8 crank, I just decided to get the new one. IIRC the bearings were ACL brand.
Are you just doing a stock rebuild or are looking to do a little power adding? A Vortec-TBI hybrid motor is a common easy power addition. The Vortec uses a superior roller camshaft, and the heads flow much better and might have higher compression.
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