Well I ordered a ring compressor from Summit the other day. It's meant for a 4.120" - 4.220" bore. My block is a 4.125" bore, so it should work, right? Well I got the damn thing and when its fully compressed, the bore inside the ring compressor is 4.190". Not nearly enough to get the rings into the cylinders. The ring compressor has "4.120 - 4.220" engraved into the side of it, so I got the ring part, maybe it wasn't made correctly, or perhaps I'm not smart enough to use it. I paid $26 for the thing so I wasn't expecting to have problems with it. Thanks for any help!

 

....i'd just return it. summit is very good with returns in my experience. tell them it did not match the description in the catalog - that it didn't get small enough.