Engine Fastener Plating, What was original

[dennisv]

I'm preparing to send off most of my engine fasteners for plating. 1970 914-6 (aka 1969 911T). I am having a difficult time telling what original finish was as what I removed is a mixture. Really hard to find good photos of unmolested original engines.

Here is my best guess. Does anyone know any different?

• Case through bolts - uncoated steel?
• Acorn nuts - zinc clear chromate (silver appearance)?
• Head nuts and washers - Black oxide (or zinc black chromate)
• Cam housing nuts - zinc clear chromate (silver appearance)?

P.S. I realize there are a lot of plating threads. Mostly focused on CAD vs zinc. I haven't found much on color / coating of specific fasteners.

[gled49]

I don’t plate thru bolts. They are either bare or phosphated.
Acorn nuts and washers are yellow zinc.
I don’t plate head nuts and washers, but it won’t hurt anything.
All hardware is yellow zinc. Don’t plate wavy spring washers, they will crack and brake.