I've got a 76 motorhome 440 with a seriously seized ring. The guy I bought it from says mice pissed in the cylinder but I'm pretty sure thats not possible considering the amount of rust I had to bore off the cylinder wall. Either way the top piston ring on cylinder 1 is rusted to the piston and after soaking it in oil for a week and trying to knock it loose with a hammer I'm pretty sure there's no way I'm freeing it in one piece. I'm looking for a single replacement piston ring but can't seem to find one. I was also wondering if replacing just one piston ring is advisable or if I need to do the whole piston or all 8. Thanks.

 

Check with your local rebuilders.... Sometimes they have some extras laying around to get rid of....

 

Sounds really like you should hone all of the cylinders and just replace the complete ring set...As you have found out rings are usually sold in sets