Friction Reducing Engine Assembly

rsicard

Member
Grumpy:

I got involved in a discussion about friction reduction during assembly of an engine. The other person was saying that the crankshaft can be easily spun after torquing the main caps prior to assembling of piston/rod combination. Just wondering what your experience is in checking the alignment of main caps, with and without bearing inserts, crankshaft main journal alignment or concentricity to make certain both the block and crankshaft are as near perfect in alignment.

It would seem that if the alignment and clearances were where they should be and applying oil pressure to the mains ALONE, the crankshaft SHOULD spin freely. As in spin it by hand easily.

Looking forward to your comments on this situation. Thanks.
 
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viewtopic.php?f=53&t=3449&p=10012&hilit=assembly+lube+moly#p10012

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http://garage.grumpysperformance.co...ng-piston-pin-height-compression-height.5064/

http://garage.grumpysperformance.co...n-wrist-pins-one-really-over-looked-part.978/

http://garage.grumpysperformance.com/index.php?threads/maximizing-piston-to-bore-ring-seal.3897/

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if you find the rotating assembly is more difficult to rotate than you expected, you may want to verify some clearance issues that get over looked at times,
theres also some, other potential issues,
theres a slight potential for the piston wrist pins too not rotate effortlessly in the piston pin bores ,

that may add to the difficulty in rotating the assembly in the block.
the piston rings must have vertical and back clearance in the piston ring grooves

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Piston Ring Groove Clearance
Pistons are grooved to fit rings that seal the cylinder’s compression and allow for lubrication of the cylinder walls. Piston rings come in a set. There are two compression rings. The top ring is affected by the most cylinder compression pressures. The second compression ring reinforces the top ring. The third ring down is the oil ring. It controls lubrication between the piston and cylinder bore.

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Place the new ring into the top piston groove, and then place a feeler gauge into the gap between the new ring and the upper land. Move around the pistons groove and obtain a few measurements. Compare this reading to specifications. If this reading is too much and the gap is too large, the piston must be replaced. The top ring takes the most compression. This causes the ring to slap against and wear the lands in the piston groove.
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and of course the pistons must have the correct piston too bore clearance. and connecting rod can only be installed facing one direction
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IM not 100% sure of your question, but a crank by it self ,sitting in a properly machined block with the bearings in place, having been coated with a decent assembly lube, and the main caps torqued in place should require no more that 10 ft lbs to spin (MAXIMUM) and in most cases less to keep it spinning, in-fact most are easily spun with finger pressure alone.
if it takes more than 10 ft lbs somethings either not machined correctly or your clearances or lube are wrong.
I generally use molly assembly lube mixed 50%/50% with marvel mystery oil as a bearing lube during assembly, and that provides a good slick surface on the bearings.
after you add the rods and pistons with the rings its resistance to rotation obviously increases but should still be UNDER 40 ft lbs to spin an assembled short block
http://www.summitracing.com/parts/CRN-99004-1/?rtype=10
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