GPracer2500
04-08-2006, 11:10 AM
I see a lot of questions about 400EX cams. I thought this might be helpful. I picked up this info from various places...if anyone sees errors point them out. The Hotcams specs are straight off their website and I called them to get the specs for the old version of the stg 2.
The lift is how far the cam opens the valve. The duration is how long it leaves it open. The more lift and duration the more aggressive the cam. Big lift and duration numbers work best at high RPM while more mild numbers are best for lower RPM.
Also, the more lift and duration of the valves the more important it is to have a high(er) compression piston. This is because with high lift/duration there is more opportunity for air to escape through the valves as the piston begins its compression stroke. With an aggressive cam some dynamic compression (i.e. the actual measured psi of compression while the engine is cycling) can be lost. This must be made up for with a higher compression piston. An aggressive cam with a stock compression piston may actually perform worse than the stock cam because too much compression is being lost through the valves being opened so much.
cam: Intake lift; Exhaust lift; Intake duration; Exhaust duration
stock............... .316, .302, 234, 238
XR400.............. .326, .321, 240, 244
HRC................. .350, .339, 254, 256
GT Thunder....... .350, .345, 256, 256
WB Track.......... .350, .345, 256, 256
WB All Around.... .345, .335, 240, 248
WEB 450/451..... .350, .345, 256, 256
WEB 479........... .378, .378, 250, 250
WEB 463/9i....... .385, .370, 272, 270
Hotcams stg 1... .354, .354, 246, 246
Hotcams stg 2... .354, .350, 254, 248
HC stg 2 (old).... .348, .349, 254, 254
Hotcams stroker. .358, .354, 262, 257
Notes:
--Numbers are listed in inches and degrees of crank rotation (lift duration at approximately .050" lift).
--The Hotcams stg 2 old version is identified by "HCDG NO. 08" etched onto the cam--not sure what the current version says.
--White Brothers All Around is etched with "WB1870".
--White Brothers Track is etched with "WB1498".
--Notice that the WEB 450/451, GT Thunder, and WB Track are all the same grind.
--Honda part number for the HRC cam (it's actually an XR400 HRC cam) is 14000-NKK-000. I don't think they are still available from Honda.
The lift is how far the cam opens the valve. The duration is how long it leaves it open. The more lift and duration the more aggressive the cam. Big lift and duration numbers work best at high RPM while more mild numbers are best for lower RPM.
Also, the more lift and duration of the valves the more important it is to have a high(er) compression piston. This is because with high lift/duration there is more opportunity for air to escape through the valves as the piston begins its compression stroke. With an aggressive cam some dynamic compression (i.e. the actual measured psi of compression while the engine is cycling) can be lost. This must be made up for with a higher compression piston. An aggressive cam with a stock compression piston may actually perform worse than the stock cam because too much compression is being lost through the valves being opened so much.
cam: Intake lift; Exhaust lift; Intake duration; Exhaust duration
stock............... .316, .302, 234, 238
XR400.............. .326, .321, 240, 244
HRC................. .350, .339, 254, 256
GT Thunder....... .350, .345, 256, 256
WB Track.......... .350, .345, 256, 256
WB All Around.... .345, .335, 240, 248
WEB 450/451..... .350, .345, 256, 256
WEB 479........... .378, .378, 250, 250
WEB 463/9i....... .385, .370, 272, 270
Hotcams stg 1... .354, .354, 246, 246
Hotcams stg 2... .354, .350, 254, 248
HC stg 2 (old).... .348, .349, 254, 254
Hotcams stroker. .358, .354, 262, 257
Notes:
--Numbers are listed in inches and degrees of crank rotation (lift duration at approximately .050" lift).
--The Hotcams stg 2 old version is identified by "HCDG NO. 08" etched onto the cam--not sure what the current version says.
--White Brothers All Around is etched with "WB1870".
--White Brothers Track is etched with "WB1498".
--Notice that the WEB 450/451, GT Thunder, and WB Track are all the same grind.
--Honda part number for the HRC cam (it's actually an XR400 HRC cam) is 14000-NKK-000. I don't think they are still available from Honda.