I will generally soak them in my parts cleaner or kerosene and have also used PB Blaster and still usually end up pounding them out.

Clean, hone, and clean cylinder walls with alcohol before appling fluid to insert seals.

~ Victor
1941 3/4-Ton Pickup (in process). Read about it in the DITY Gallery
1955 Grumman Kurbside "Doughboy" 235/3 on tree w/ OD
1957 3100 - moved on
1959 C4500 Short Bus "Magic Bus" - moved on
1959 G3800 1 Ton Dually "Chief" - moved on
1958 C4400 Viking "Thor" ~ moved on to fellow Bolter