I have a friend of mine who I'm helping rebuild his Mitsubishi engine, 2.6 4 cylinder. We've got a new set of rings, same set of pistons (didn't need boring) and a ready block.
I cleaned the piston grooves with a broken piece of ring & installed the rings. They're installed correctly (in this case, bevel up). I get out the spring compressor and compress them, then start installing the piston into the cylinder (arrow facing correctly). I get the piston all the way in (all 3 sets of rings are into the cylinder), and then no more. It literally takes heavy hammering to even slightly move the piston. I get the piston back out, and none of the rings have popped or are bent; they're all in the proper grooves, undamaged. There's no scoring of the cylinder wall that might indicate a ring dragging.
I inserted the rings into the cylinder without a piston, thinking maybe there wasn't any gap once they compressed, but they still have a gap all the way down the bore. The rings themselves seem to compress and expand very easily within the piston grooves. The pistons slip easily into the bores with no rings on them.
The machine shop, which cleaned up the block & honed, made sure there wasn't any ridge on the block (there really wasn't any to begin with). I've tried soaking these pistons in oil, oiling the cylinder wall heavy, etc. Still, it takes an inordinate amount of pressure to even budge these things. I compared the new rings to the old ones and they're the same size. I've got the pistons going back into the same bores they came out of. The rods aren't hanging up on the crankshaft or anything like that.
I'm at wit's end here...I can't, for the life of me, figure out what could be making these pistons so hard to install. Does anyone have any ideas of things I might not have covered here???
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