Some of the holes had real taper plugs, pipe threads. Two of the taper holes were about 10mm and somebody had forced straight thread bolts into the taper holes, ruined the threads. I might be able to chase them and put in 1/8" taper pipe plugs. I don't know that the bolts made a good seal. I"ve verified that some of the threaded holes are 1/8" NPT 27, I'll chase the threads and with teflon tape will repair the holes. I have a 1/8" to barb adapter I can connect my vacuum gage, haven't used it in years. Jim