Working with a 70 big block engine. My question is were all the fasteners done in black phosphate ? Talking about intake bolts, valve cover bolts etc.

Thanks!

yes

but then engine color

EDIT,
excluding motor mount bolts, clutch fan bolts, = clear zinc

Ok ! that's what I thought but just wanted to be sure.

Thanks.

Can't speak for big block, but on my 1969 340, a few engine fasteners are zinc plated. For example, the 12 intake manifold to head fasteners are yellow zinc then engine painted.

Probably the reason for yellow zinc fasteners in the intake manifold is because the coil is attached to it and grounded to it.

Fasteners for head to firewall ground and negative battery cable to head are also yellow zinc then painted engine color on my 340.

Get a cup with a little muriatic acid in it and drop bolt in it if it's zinc acid will boil like alka seltzer. If it doesn't boil it's not zinc. Other finishes do nothing.