I installed the 1977 piston in a 87 model 880 and can hear it hiss around the valve seal when the pump head is bottomed out. As soon as I pull the pump lever up it stops. So there must be some interference with the abutment and piston head. I think it would take a lot of trial and error cutting piston rod pivot holes to get it just right. Given my schedule and lack of piston rods I'm willing to ruin, I think the 1977 piston in the older style guns is a no go. To get it to work the cylinder must be notched further like the newer guns. I used a spare piston rod and cylinder for this test but I am going to put the originals back in and enjoy the ole girl just the way she is. So 1977 upgrades are a definite improvement for the newer style 880s (non-brass non-ringed cylinder) but won't work for the older style guns without a custom piston rod. I have two 1977 piston rods I have no use for so one day I may revisit this for the old style guns.
Quote from: pblawler on November 18, 2022, 02:47:45 PMI installed the 1977 piston in a 87 model 880 and can hear it hiss around the valve seal when the pump head is bottomed out. As soon as I pull the pump lever up it stops. So there must be some interference with the abutment and piston head. I think it would take a lot of trial and error cutting piston rod pivot holes to get it just right. Given my schedule and lack of piston rods I'm willing to ruin, I think the 1977 piston in the older style guns is a no go. To get it to work the cylinder must be notched further like the newer guns. I used a spare piston rod and cylinder for this test but I am going to put the originals back in and enjoy the ole girl just the way she is. So 1977 upgrades are a definite improvement for the newer style 880s (non-brass non-ringed cylinder) but won't work for the older style guns without a custom piston rod. I have two 1977 piston rods I have no use for so one day I may revisit this for the old style guns.Mr. Trey,I believe the 1977 piston is longer to accommodate the coil spring and 2 O-rings.If you installed it on a standard 880 pump link, the resulting assembly would indeed be longer.....
Patrick!!!! You are the man!!! The 1977 piston head is bananas in my 880 .22 conversion. I don't have a Chrono but these crosman hp 14.3 grains get to 20 yards really fast now. I used to be able to see them travel. Not the case now. I'm going to upgrade the head on my .177 Daisy 901. Happy Thanksgiving airgunners!