1981 CJ7 Restoration - 2021.09.10

Next up are the pistons. These are brand new pistons with the rings gapped and installed by the machinist, which saves me some work, so I am grateful for that. They are 0.030" oversized to accommodate the over-boring of the cylinders. The pistons were also pre-attached to the connecting rods, so all I really had to do was align the rings and install the bearings and push in the pistons.

I bought an ARP cone style ring compressor which just sits on top of the cylinder and you just slide the piston through and tap it down. The original recommendation was for the Hastings 1134 ring compressor, but the reviews for the ARP tool were far better. The only drawback with the ARP tool is it will only service one size of piston since each sleeve is machined to a specific diameter. The rings should be oriented so that the gap of the next ring is 180-degrees from the previous, alternating until done. The wavy oil ring should be 90-degrees from the others.

They say you can't use too much oil to help the pistons along during the installation process. I'm glad I had the drop cloth beneath the engine. Got all 6 in and used the Plastigage on one of the rod bearings to measure the clearance - again, 0.002"

Torqued all the nuts on the rod caps to spec and everything spins smoothly. There is some resistance, which is to be expected, but it's smooth and consistent.

All 6 pistons are in, facing the right direction and everything turns smoothly.

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