One of the problems with old kits like this is that over time, the molds get worn out, and the mold halves no longer align precisely during the molding process. What you get are parts–especially parts that are round or cylindrical, like pipes–where the two halves don't align. In other words, the right half and left half of the part is mismatched, sometimes so much so that the offset is almost 1/16 inch. On larger parts you can fix this by sanding away the mismatch until the part is smooth and the offset seam is gone, but on small parts or parts with a small diameter, sometimes sanding the mismatch all the way off leaves you with an undersized part.
A lot of the parts on this kit have this problem, and it's incredibly tedious to clean up all the various pipes, valves and fittings... a lot of sanding and filing, Here are a couple of typical parts that had this problem and had to be cleaned up a lot to get them to look this good. I probably spent close to a half hour just on these two parts alone... and there are a lot of similar parts in this kit:
But after cleanup and some paint detailing, they look pretty good. It's just a pain to get them to this point: