Thanks for the replies.
Food for thought
stuey

stuey, if your manifold is off or you trust your drilling and tapping with grease on them many of the aftermarket manifold have the heater hose threaded fitting facing forward on the left side of the crossover. You may see what it looks like by looking on the net for Y-Block intakes. Just another option..

56 Vic, B'Ville 200 MPH Club Member, So Cal.

... why do some heater hose nipples have an extended tube into the manifold?

The reason is that the extended tube will pickup/draw full coolant from the bottom of the crossover. If the coolant is aerated (as most is without a coolant recovery system) and if drawn higher the coolant may contain air bubbles that could be drawn into the heater core possibly causing an air lock.

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Hello everybody all the pepes.
Was thinking how I could connect a heater hose and an electric fan sensor into the same npt hole in the intake manifold. 
Looking at various adaptors, why do some heater hose nipples have an extended tube into the manifold?
Thanks.
stuey