Hi Vince,
First of all you would have to determine what type of keepers you will be using, cotter pin, straight pin, split ring etc. This will determine the procedure for making the valve.
If the valve stem requires a groove near the top for a c-clip or spit ring type keeper then here's the steps that I would use.
1. First chuck up your piece of stock leaving enough for the entire valve. Lets say the stem is .094 diameter. Cut only enough material down to .094 to use whatever grooving tool you are going to use. This will keep the stock rigid for cutting the groove.
2. Now cut successive short lengths of the stem down to the .094 dimension until you get close to the valve head. I usually leave .0005 for polishing to the finished size.
3. Now using a cutter with a radiused nose clean up the bottom of the stem up against the head of the valve. This does 2 things. It strengthens the valve head and helps the fuel flow more smoothly into the port.
4. You could at this point have your compound set at 45 degrees to cut the seat angle but I have found that with the compound turned over that far it's hard to use the other tools for cutting the stem so I just leave it for later.
If you are making a valve stem with a cross drilled hole for the keeper wire then just do steps 2-3.
5. Cut the valve off leaving .01-.02 for cleanup.
6. When you get the valves cut off chuck them in an appropriate device to face them off to size and cut the valve seat area. I have a small set of ER collets that are held by a home-made set-true adapter that screws onto the nose of my lathe. I insert the valve, indicate it and adjust the chuck until it's dead true then cut the length and face.
7. Now back to the cross drilled hole if that's the type you are using. Make up a small fixture with the diameter of the stem in one side and a threaded hole in the other. The threaded hole is to adjust the position of the valve to get the cross drilled hole in the correct place. Now cross drill the fixture for the diameter of the pin or cotter pin you will be using. With the valve inserted and it's position adjusted you can now drill the cross hole.
As an optional method and one that works quite well you can make built up valves. Using standard diameter stock for the stems you can cut them to length allowing enough stock to protrude slightly through the valve head when assembling.
Make up small discs for the heads and try to drill the through hole about .001 larger then the stem. When you get ready to silver solder the stem and head together make a small dimple on the stem where it will fit inside the head. This will keep it from moving when heat is applied and the clearance will allow the solder to flow around the head and stem.
I hold the stem with a small machinist's clamp with the head facing down. I flux up the assembly and cut a small piece of solder and set it on the head. By applying heat to the bottom of the head it will melt the solder and draw it toward the heat. Try to cut the piece of solder big enough so that it will flow through and still make a nice fillet up against the head and stem.
After cleanup chuck up the valve as stated above and cut the head length and seat face.
gbritnell
