Is it a small or big block? Don't think the rope would work well on a slick finish journal. If it has been line bored a lot, that may be your problem. On chevy's they make special main seals for line bored blocks. On mopars I don't know of any. But what I do is take some brass shim stock and silicon and insert a shim on the seal where it slips on the block and cap, this presses the seal a little tighter and will compensate for the material removed during line boring.