Timely post for me (and anyone else interested in a correct stock restoration) that you made here Philip-------and exactly as you said in your reply just now Charles!!
How would you describe the finish as shown in the photos of this NOS valve cover??
Raw aluminum, as from the mold, satin finish???
Do you think there were any additional treatments or processes used to remove casting flash or surface/ finish irregularities?
Attached is the judging sheet I received for entry of Zilver, my 1973 240Z, at the 2019 ZFest/Zcon held in Branson this past summer.
1 Zup Daniels 240Z stock.pdf
The most difficult point deduction for me to understand regarding the comment of the judges was regarding the finish of the valve cover.
ENGINE and ENGINE COMPARTMENT Comments Deduction
2. Engine block / oil pan / cylinder head valve cover finish blasted 1
My query is this:
What is one to do?
This photo is from engine restoration prior to Zcon 2015 in Memphis when I entered Zilver in "240Z Street Modified" class----before I made the conversion back to the original flat tops.
After 47 years of accumulated use, (being subjected to oil changes, valve adjustments and all other manner of possible maintenance issues) certainly most, if not all, valve covers will need some form of restoration back to "as from factory" condition. Paint, polish or plating are obviously not correct finishes.
At the time of my restorative efforts I chose to have the cover bead blasted with a very fine USED glass bead. It almost had the consistency of flour and the cover was gone over several times until there was an even surface appearance and texture. Satin finish---no gloss or swirl---it looked very much to me like the NOS example you linked above.
I then applied GIBBS BRAND OIL to the cover liberally, several times, removing the excess after several minutes so there was no pooling or surface wetness.
The GIBBS penetrates into the pores of the metal and (because it is there first) prevents the entry of anything in the way of water, other oils, dirt or combustion soot from adhering or accumulating and its anti-corrosion properties prevent oxidation of the aluminum (white spots or flaking). A simple rinse with Dawn detergent mixed with water over the surface followed by a thorough rinse from the garden hose with clean water, allow to dry, and a re-application of the GIBBS oil has maintained the cover for the last 5 years. Zilver is no "garage queen". The car is frequently driven locally and has been driven from N.W. Arkansas to and back from each of the Zcons attended. (Memphis, Austin, Atlanta and Branson)
I don't know of any other way. In agreement with what Charles said above----What would the judges have us to do if not bead blast????
This is not "sour grapes" or meant to be a slam on the judges but-----