All of my 55 motors have had rope seals and shims with the exception of the early 56 motor (date coded late 55) I am currently redoing which had the neoprene seal installed. GM changed the bearing style in 56 so 55 motors still used a dowel style main bearing, shims, and a rope seal but 56 and forward used tanged bearings, no shims and neoprene. I cant remember whether the neoprene seal was first identified in the shop manual, 56 or 57 so I will check that. The rear main cap in the 55 and earlier blocks are not machined for a neoprene seal, specifically not machined accurately enough to use the seal. The did not need to be and the rope filled the area. That being said, the neoprene will physically fit but will not work. As for the rope seal, the most reliable sold today is the Best Gasket version but there is a rub. The older rope seals had an asbestos component to them. They were a little trouble some as there was somewhat of an art to installing them but even by 53/54 they were really obsolete, designed for the earlier low pressure or splash oiling motors, and not really all that effective for the later full pressure motors. In other words, the rope sealed motors still dripped a bit. Todays rope seals use a fiberglass graphite product. Its ok, I have gone down the middle on two motors (a 54 and a 55). The 54 did fine with the Best Rope, still drips here and there (Its in a buddy's 54 pickup) but the 55 leaked within 1000 miles and we had to redo it. I used a older rnos felpro that I had (the instructions were dated to the early 70s) and that seems to have done the trick. My opinion is that older rope seals work a little better. So you might consider kicking the bushes for a real GM seal or an older Felpro, victor, McCord or like rope seal.
Last edited by Dragsix; 04/11/2018 9:18 PM.
