Since we were out of the correct size for the new exhaust seats (and it was a holiday weekend) I jumped over to working on the block a little. I had scored a set of breather tubes for the lifter galley out of an engine I was stripping for scrap at the shop a few weeks ago. Someone had blown up something and swapped all their good parts over to a new shortblock and left the old one with the tubes in it. They're not the fancy looking aluminum ones but will do the same job so they're perfect for my no budget build.
The block needs to be threaded in order to insert the tubes and plugs so while I was at it I threaded the end holes for plugs also. To thread the holes first a tapered reamer is used on a drill to chamfer the top of the hole so its easier to get the tap started. Then cut threads with the tap. Because these are tapered pipe thread the depth is checked on the first hole and then the tap is marked and the rest are tapped to the same depth.
Here's a pic of the reamer and tap . And then a pic of the vent tube and a plug. Bottom pic is the end of the block where plugs get installed.
