Following Ted's advice, I have manufactured a new fixing piece for the distributor

I've seen these guides in some heads

One of the procedures that can be utilized to restore the clearance of the valve stems in worn valve guides is called knurling.  This might account for the continuous groove that you see on the inside bore of the valve guides pictured. 

I'm not familiar with the half round opening that has been machined in the end of the valve guides pictured.  They may have been added using a two or four lip straight end or ball end mill cutter.  I'm speculating that their intent is to serve as a shallow reservoir for capturing a small amount of engine oil from the rocker arm assemblies to assure some engine oil lubrication to the valve guide and valve stem.    Again, I have not seen these half round openings utilized before with the knurling process.  John (Hoosier Hurricane), Ted Eaton or other Forum members may have a better handle on this.

Valve guide knurling is an alternative to using replacement valves with oversize stems, installing replacement guides, or machining the existing worn guides to permit installing bronze sleeves in the valve guide bores.

Hope this helps. 


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

Charlie, one of the better quality knurling outfits uses a guide rod with an exposed hardened roller that protrudes above the surface of the guide rod.  There is a drill ;guide included in the kit that is slipped into the guide and a standard drill bit is used to machine the notch you noticed at the top of the guide.  The knurling tool is then inserted in the guide with the roller indexed into the notch and is powered with an electric drill to gently roll the guide material so that the guide can be reamed to fit.  The notch allows the knurling roller to start, the roller is set at a slight angle in the tool so that it "screws" itself down the guide.  I used one of those kits when I worked in a NAPA machine shop years ago.

John - "The Hoosier Hurricane"

thanks guys for the clarifications 👍

Hoosier Hurricane.  Thanks, John.  I appreciate your description and explanation.  It sounds like a time consuming process if all the valve guides needed to be knurled to return them to tolerance.
Charlie


NoShortcuts
a.k.a. Charlie Brown
near Syracuse, New York

today the new rocker adjusters have arrived, they look good

I am manufacturing a pulley for the power steering pump, any comments or advice is welcome

Copelo, it's very difficult for me to determine with my eyesight but that isn't aluminum, is it? If it's steel and you left a small gap between the two pulleys to allow for some flexing and sxpansion, then I think it should work OK.  Nice machine work,  JEFF.................


64F100 57FAIRLANE500

Thank you, yes it is aluminum