I'm just starting to do Bob Hoover's HVX engine mods for a 1973 VW Type 1 case. The case has been machined for 92 mm pistons and cylinders, welded behind #3 cylinder, welding sometimes tends to warp the case and good idea to have it checked and if warped have the main bearing saddles line bored. I had the case checked at a VW Type 1 only machine shop. Everything OK. Also cleared for a stroker crank if I wanted to make it a 2180 cc engine. Decided to use the stock 69mm crank for 1835 cc engine. I had great success in the HVX mod in the 1835 cc engine in the SSSC aircraft. With the increase oil flow to the rocker arms and heads I had no heat problems in a WOT climb as long as I wanted on a 100 deg OAT day. To get a better understanding of the Mods read all of this. https://bobhooversblog.blogspot.com/2007/05/hvx-mods.html The only down side that I have found is with the increase oil flow to the heads you will have a slightly lower oil pressure. But that is easy to take care of by going to the larger capacity oil pumps or what I did. The stock oil pump cover uses a .004 paper gasket, I made a new gasket of .002 gasket material from NAPA and raised the oil pressure about 8 to 10 pounds at cruise rpm of 2650/2700 rpm, went from 32 lbs to 42 pounds. I always drill out the oil passages soft plugs and tap for plugs. Only way to make sure the passages are clean from an machine shaving with the case was made,etc. EMPI makes a kit of all the plugs you will need for $10. If used for an aircraft engine the soft plug just right of the full flow inlet elbow on the pulley end of the case will need to be drilled out and tapped and plugged. http://www.greatplainsas.com/service1.html The plug has a .040 step made into it to act to act as an orifice that supplies oil to the #4 main bearing. When using a prop hub the load on the bearing is much higher than the auto alternator belt and the bearing needs more oil. One of the things that Scott at Humble Engines and Great Planes do to the cases they sell. Next will be taping threads for the plugs, and doing the mods on the lifters and rocker arms and shafts. After that I need to get it as clean as possible, install the plugs with Lock-tite and paint a light coat of flat black paint on the outside of the case to stop any corosion. No paint on surface that get bolted together.