Chris, I've made these a million times building engines, in fact I will make one tommorow for the MGB engine I'm putting the final touches on (MGB and Spridget pressure relief valves are the same). I can usally zap one out in 15 minutes or less. Here's what I do, maybe this will help.
I drill the cap nut from the inside, it has a point in it on the inside so it's much easier to hit the center by drilling from the inside. I tap it for 1/4-28. Then I use a 1" or 1 1/4 long hex bolt (all threaded). On the bench grinder I just knock the corners off the hex bolt head so it will fit nicely within the cap nut. I also grind/belt sand all the markings off the top of the head of bolt so the spring has nice level seating area. I then thread the bolt from the inside of the cap nut, so that the threaded end of the bolt comes to the outside of cap nut, I then use a jam nut and thread on the end of the bolt. I put a slot in bolt so I can adjust with a screwdriver ( I use a hand grinder and cutting disc to make the slot, works nicely) . If you are using a gear reduction starter you don't have alot of room to work with on the outer side, I found it easier to get to with the screwdriver slot witha shorty screwdriver than getting a allen head wrench in this area. There are ones for sale out there with a knurled knob on them, these will work fine on Minis but not on the Spridget or atleast with the gear reduction starter. I also more often than not use the 9/16" ball bearing rather than the stock cup what I do for length is I measure the free length of the stock set up and then measure the free length of adjustable unit with it fully adjusted toward the outside with the ballbearing and cut the spring to equal the stock length, as now you can adjust inward to increase pressure.
Chris, feel free to email me at home,
hapfp@charter.net, I have some pictures on this computer of one of these I made and will gladly send them to you. It's a piece of cake, you can do this with just a few simple tools, no biggie.
To answer the question asked above about why you would want to do this. By being able to set your cold oil pressure by adjusting the pressure regulator you can somewhat govern your hot oil pressue which oil pressure drops as it gets hot. Say for example you crank your car and the cold pressure is 60 pounds and once it heats up you at 50 pounds, but you would like to have 80 pounds cold pressure and 70 pounds hot pressure then a reglator will let you do this. All oil pumps and presure relief set ups even if new will not alway net you the oil pressure you want and a adjustable pressure regultor lets you better control this.
Hi Guest!
Hey - did you know if you click on the title of a thread it will take you to the first unread post since you last visited that thread?
but were afraid to ask: 
STOP!! Never post your email address in open forums. Bots can "harvest" your email! If you must share your email use a Private Message or use the 
smilie in place of the real @
Pretty Please - add it to our Events forum(s) and add to the calendar! >> 
