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ursus · 09-23-2023, 01:23 PM

I acquired a stock Model B short block that was rebuilt and put in storage about 15 years ago. At first it was difficult to turn it over but after flushing out the cylinders with WD-40 I can now turn it through full revolutions with about 25-30 pounds showing on the torque wrench.

However, there is much greater resistance as the pistons are moving through the middle of the cylinders, which is the area of maximum side thrust. There is much less resistance when the pistons are at the top or bottom of a stroke. I pulled one piston and found the ring end gaps to be 15-18 thousands, nice cross hatch on cylinder walls, and both rod ends to be in spec.

Is it normal for newly rebuilt engine (rebabbited mains and rods, new pistons, rings, etc) to exhibit greater resistance as the pistons are moving through the middle of a stroke?

P.S. I only have experience with engines that were partially rebuilt, and never with a fully rebuilt unit that hasn't been run.

09-23-2023, 01:23 PM	#1
ursus Senior Member Join Date: May 2010 Location: Oregon Posts: 1,379	Rebuilt Engine Piston Resistance I acquired a stock Model B short block that was rebuilt and put in storage about 15 years ago. At first it was difficult to turn it over but after flushing out the cylinders with WD-40 I can now turn it through full revolutions with about 25-30 pounds showing on the torque wrench. However, there is much greater resistance as the pistons are moving through the middle of the cylinders, which is the area of maximum side thrust. There is much less resistance when the pistons are at the top or bottom of a stroke. I pulled one piston and found the ring end gaps to be 15-18 thousands, nice cross hatch on cylinder walls, and both rod ends to be in spec. Is it normal for newly rebuilt engine (rebabbited mains and rods, new pistons, rings, etc) to exhibit greater resistance as the pistons are moving through the middle of a stroke? P.S. I only have experience with engines that were partially rebuilt, and never with a fully rebuilt unit that hasn't been run.