The 386 is useless. Its a 2800rpm spring, same as stock or maybe 100-200 rpm more. If one was to install a gov spring, you'd want to put in a 3200 if you went to the trouble of doing it. Pastor Bob posted some other gov spring part numbers to try out, those would be the ones to investigate, I already put my $30 into the R&D fund, to find out the 386 is 2800rpm and useless, and the 374 is 1/8" longer than 366, useless?? Don't know just yet. Love to find a 3800-4500 rpm spring that is the same length as the 366 3200rpm spring.