up to the early 70's the most common practice to make engine block and head cores was to use
a method called 'oil sand'. In to a mold that was the shape of the desired core, a mix containing:
sand, oil, wood flour, and some times ground iron oxide was packed or blown. The mold was
flipped over allowing the shaped sand mixture to lay on a flat plate. The sand mix on the flat plate was
then ran through an oven. Out of the oven came a hard core that was the shape of the original mold.
Thin areas of the core were reinforced with wires, specifically cut to shape and bent to fit the core profile.
The wires were placed in the mold and the uncured sand packed or blown around them. In a large foundry there
could be a whole department dedicated to the production of the various shaped wires. The core wires
would have their own part print, specification for diameter, length, profile, dies,,,.
Those are the wires that you are finding. Some large wires, the size of reinforcing rods used in concrete
were re claimed from the spent core and mold sand and were used multiple times. In the subsequent cleaning
and processing of the castings attempts were made to remove the thin wires, but it was known that not all
wires were retrieved.
In the '70's furfural or 'hot box' core making replaced the oil sand method. With hot box the core pattern
is heated to 300 to 600 degrees F, the sand mix is blown into the core box under high pressure, the core sand
cures / takes a set, then is extracted from the core box. The hot box process eliminated the need for wires and
provided a substantial improvement in productivity and accuracy.
In the 80's the 'cold set' process came into use. Cold set is not far removed from two part epoxy, where there is a
chemical reaction that causes the polymers that are coating the sand grains to bind together without heat.
The 'cold set' process resulted in a further improvement in productivity and a huge increase in accuracy.
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