It's not real infrared, response starts to take a dive at
680nm is 5 stops down at 750nm.

Kodak HIE's response curve is rising to a plateau at 750 and
doesn't tank until 950+.

An #88 filter blocks at 735nm where the film is 4 stops
down, so speed is really 25, not 400, and 25 is most
likely an optimistic number.  Unless you happen to
have a near-ir photometer handy exposure is a
guess and a prayer until you get the hang of the stuff.

Without a filter it isn't going to look IR.  With a
#25/29 it will look infraredish, but not that spectacular
IR effect with bright white trees and jet black sky.
If you really want to play with IR get some HIE and a
#87C filter.