That's ISP in seconds, needs to be in m/s, so I *think* you times it by 9.8 m/s^2 (seconds cancel out, you're left with m/s) = 1381 m/s. I could be wrong, however.
s1cinter:Velcro/s1cinter
STATUS Landed Earth
BASE Cape Canaveral:6
HEADING 0.00
TGT_HEADING 095.0
FUEL 1.000
CONFIGURATION 0
CAMERA 0 0 90.0
SERIESBURN 0 S-II 0.0 0.0 -9.25 0.0 1.0 0.0
END
S-1C:Velcro/S1C
STATUS Landed Earth
BASE Cape Canaveral:6
HEADING 0.00
TGT_HEADING 095.0
FUEL 1.000
CONFIGURATION 0
CAMERA 0 0 90.0
SERIESBURN 0 s1cinter 0.0 0.0 18.25 0.0 1.0 0.0
END
; === Configuration file for vessel class Generic CVEL stage (Saturn-IC booster interstage) ===
Module = Velcro
Meshname = Velcro/Parts/s1cinter
Size = 24.0
Mass = 5000 ; empty mass [kg]
MaxFuel = 5000 ; max fuel mass [kg]
Isp = 2820 ; fuel specific impulse [m/s]
IspSL = 2430
MaxMainThrust = 3000000.0
MaxRetroThrust = 0
MaxHoverThrust = 0
MaxAttitudeThrust = 1.0
COG_OverGround = 4.0
CameraOffset = 0.0 0.0 18.06
CW = .2 .3 .7 .7
LiftFactor = 0.0
CrossSections = 120.0 120.0 65.0
RotResistance = 0.7 0.7 0.3
Touchdownpoints = 0 4.4 -24.1 4.4 0 -24.1 -4.4 0 -24.1
; === Attachment specs ===
BEGIN_ATTACHMENT
C 0.0 0.0 18.06 0 0 1 0 1 0 VELCRO1
C 5.25 0.0 0.0 0 0 1 -1 0 0 VELCRO2
P 0.0 0.0 18.06 0 0 1 0 1 0 VELCRO3
P 5.25 0.0 0.0 0 0 1 -1 0 0 VELCRO4
END_ATTACHMENT
; === Engine reference points ===
ExhaustType = SRM
MEngineRef1 = 5.5 0 18.12
MEngineRef2 = -5.5 0 18.12
MEngineRef3 = 0 5.5 18.12
MEngineRef4 = 0 -5.5 18.12
MEngineRef5 = 3.89 3.89 18.12
MEngineRef6 = -3.89 3.89 18.12
MEngineRef7 = 3.89 -3.89 18.12
MEngineRef8 = -3.89 -3.89 18.12
SLSICPS:Velcro\slsICPS
STATUS Landed Earth
POS -80.6745292 28.5191812
HEADING 0.00
ATTACHED 2:0,SLSinter
AFCMODE 7
PRPLEVEL 0:1.000000
NAVFREQ 0 0
CONFIGURATION 0
PRIMEBOOSTER 1
CENTERTHRUST 0
IGNITENEXT 0
PADBIAS 1.000000
CAMERA 0.000000 0.000000 75.000000
TGT_HEADING 0.000000
END
SLSinter:Velcro\SLSinter
STATUS Landed Earth
POS -80.6745292 28.5191812
HEADING 0.00
ATTACHED 2:0,slsCORE
AFCMODE 7
PRPLEVEL 0:1.000000
NAVFREQ 0 0
CONFIGURATION 0
PRIMEBOOSTER 1
CENTERTHRUST 0
PADBIAS 1.000000
CAMERA 0.000000 0.000000 90.000000
TGT_HEADING 95.000000
SERIESBURN 0 SLSICPS 0.0000 0.0000 -48.6 0.0000 0.0000 -1.0000 0.0000 1.0000 0.0000
END
slsCORE:Velcro\SLSCore2
STATUS Landed Earth
POS -80.6745292 28.5191812
HEADING 0.00
ATTACHED 2:0,slstower
AFCMODE 7
PRPLEVEL 0:1.000000 1:1.000000 2:1.000000
NAVFREQ 0 0
CONFIGURATION 0
PRIMEBOOSTER 1
CENTERTHRUST 0
PADBIAS 1.000000
CAMERA 0.000000 0.000000 90.000000
SLA 1 0.50 0.00 -1.00
TGT_HEADING 95.000000
SERIESBURN 0 SLSinter 0.0000 0.0000 0.8000 0.0000 0.0000 -1.0000 0.0000 1.0000 0.0000
END
Try this second stage version. This has a newer tower mesh
https://dl.dropboxusercontent.com/u/71242599/SLS2NDSTAGELAUNCH.zip
It has the Altair lander from here:
http://www.orbithangar.com/searchid.php?ID=6621

From my understanding the SRB's will burn for 124 seconds, then the core stage will continue to burn for about another 8 or 9 minutes then the upper stage will separate and ignite its engine. The fairings and the launch escape tower jettison after the upper stage fires.
The constellation video kind of shows this sequence.
https://www.youtube.com/watch?v=bd-a__zQlJU