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hi guys i'm building my first motor and i'm cinfussed about platigauge , the problem is that ive had the crank polished (stock) ive put the new bearings in and torqued them down but the plastigauge semms to have spread nearly 1/2"on the crank does this seem right ,thanks martin
 

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martin c said:
had the crank polished (stock) ive put the new bearings in and torqued them down but the plastigauge semms to have spread nearly 1/2"on the crank does this seem right
You are correct- this isn't right.

It may be several things:
  • Are the caps aligned as they were before the engine was disassembled? They need to be correctly orientated, and back in the exact same position as they were before.
  • Is this the rods, mains, or both? If both, I would highly suspect the wrong application or size of bearings.
  • Are the parts immaculately clean? There can be absolutely nothing between the bearing shells and the caps/rods/main bulkhead. NADA!
Get back with whether or not the rod caps and mains were marked for position and if the reassembly was the same as disassembly.

Double check the bearing part numbers for correct size (in your case, STD. Not -0.010, 0.020, etc.) and application. The undersize will be etched into the back (convex) side of the bearings. As will the part number- see that the number on the bearings matches the box from where they came.
 

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Which color plastiguage are you using? Red, Blue, Green? Different colors for different clearance measurement ranges. You should be using Green. If green is spreading that far, something is wrong.
 
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