Mystery hole question

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Joined
Jan 20, 2022
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Location
Homer Glen, Il
My Car
1971 Mustang Mach 1 351c FMX trans and 9 inch rear end
I am new to Ford engines and am wondering what these holes in the 4V closed chamber cylinder heads are. I noticed them when the engine came back from the builder. The engine was broken in and dyno tested so they don't seem to affect drivability. I can't see too far down them and I loaned my boroscope to a buddy last week so I can't see how deep they are or where they lead. Any info would be appreciated, at this point I am assuming they are nothing to worry about but just thought I would ask. Thanks
 

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I guess there are several theories of the purpose of this hole(s). I remember asking about it at the Ford dealership I worked at one summer. One mechanic told me it was used as a locator point in machining the heads, and another told me in an older engine design, it was used to route air to a riser for the choke system, long replaced, but the initial bores hole remained. IDK if any of those are true, but there you go.
 
That hole is machined into the casting for a machining tooling locator pin, at the factory. after machining, it has no purpose. You will find two holes machined, one at either end of the pan rail, on the underside of your block as well. They locate the casting as it is machined.
 
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