nPI Heads:
Combustion chamber volume: 51cc *
Intake port volume: 146cc
Intake valve diameter: 44.5mm
Exhaust valve diameter: 34mm
Intake flow @ .500 lift: 156cfm
Exhaust flow @ .500 lift: 116cfm
nPI Cams: .480 lift (duration at .500 = 204 intake, 208 exhaust)
* Initial 4.6L engines utilized flat top pistons.
PI Heads:
Combustion chamber volume: 42cc **
Intake port volume: 159cc
Intake valve diameter: 44.5mm
Exhaust valve diameter: 36mm
Intake flow @ .500 lift: 156cfm
Exhaust flow @ .500 lift: 133cfm
PI Cams: .535 intake, .505 exhaust (duration: 192 intake, 184 exhaust)
** PI equipped engines utilized dish pistons to keep the compression ratio at 9.7-1.
in there it says that npi cams have more duration and less lift. the pi cams have more lift but less duration. so modular engines like more lift than duration :dunno: or is that a typo??? i would think duration would give more power than lift??? at least on most other engines thats the way it works.
