Valve Covers: Shiny or Matte Finishes 69 z28

[WaltZ]

when did 69 z28s change from satin matte to shiny polished valve covers, or were they all polished.
does it have anything to do with drippers and no drippers, and if so when where they changed out.
Thanks in advance.

[camaronut]

They were never polished. 

Always matte finish.

[jdv69z]

Pic

[69Z28-RS]

Although not polished, the '70 and later ribbed aluminum covers always seemed a bit shinier to me, and in the mid-late 70's, they got shinier yet.   Some 'late '69 Z28s and other higher performance Corvette engines (350/350) got the 1970 model valve covers in the factory (with drippers).

[rszmjt]

70 covers are still dull, IMO, I have a 6000 mile LT1 engine and the covers appear to have the same sheen as my 69 Z28 non dipper covers. The 70 covers have drippers. I also have a set of survivor 70 take off covers and they too are dull. When I was at the Corvette shop for 20 yrs, i noticed that the dull finish ended about 1973/1974.  Also in 1972/1973 the cut out relief on the upper flange got bigger on 1 cutout to accommodate for EGR provision.
The shiny polished covers were a GM service part offered through GM performance parts. They almost all have only the inner flange to retain the gasket. Early production covers had double flange rib I’m thinking till about 1978? When they showed up black finish on L82.

[firstgenaddict]

They were pressure cast aluminum, smooth and sometimes show aluminum grain.

FWIW The ones available over the counter are the only ones I have seen which are truly polished.

Here are the ones on my 71 vette survivor and my brother's 73 L82 vette survivor.