[woodz428]

If you are referring to FE engines, I always put restrictors in. I take a little different approach, but 20+ years of doing it haven't created any problems. Instead of restricting oil between the block and head I do it at the feed hole to the rocker shaft. I fit a hex piece (like an oil pump drive) rod that is just the size of the hole. I round off both ends and make sure that it doesn't interfere with the rocker stand, and then set it in. The reasons are many that I do it that way. If the restrictor should get plugged,it is easy to remove and clean, but that hasn't ever occured. I also believe that the hex allows more area for oil to flow than does a small restrictor hole and is less easily plugged with any small material that may find it's way in to the oil system. Although I used the oil pump drive reference to illustrate the shape, I never use a hardened metal, and the fit within the hole is important to keep it from moving around under pressure and creating metal fragments. Others put a small orifice in the block feed hole to the heads. I would suggest that either one is O.K. however, I use my method because it has served me well. When you build engines for others, it sometimes takes unique solutions to old problems that make them long lasting and trouble free.