I've changed the cambelt, water pump and pulleys on my mk1 1.6 mx5 long nose.
Following this guide, I've set the tension for the cambelt:
This from the "Garage Section":
# Turn the crankshaft 1 5/6 turns clockwise
And align the timing belt pulley with the tension set mark.
# Tension the belt
Loosen the tensioner bolt to apply tension to the belt. Tighten the tensioner bolt to 37-52 Newton Meters.
# Turn the crankshaft 2 1/6 turns clockwise
Verify the timing marks are still correctly aligned.
# Check belt deflection
Apply about 22 pounds of pressure to the center of the belt between the camshaft pulleys. The deflection should be 9-11.5mm. If not, repeat from the tension setting.
Also looked into this guide that was helpful:
Anyway the belt is still making a whirring noise, sounds like a supercharger, the belt is obviously tensioned too tight or could it be the sounds of a new belt that needs wearing in?