so I'm looking into getting a new cam and was wondering a couple things. I'm going to use a couple example cams to try and make my point a little clearer.

the first is the Comp 280 xfi:
duration @ .006 280/288,
advertised duration 230/236
lift 5.7/5.76
lsa: 113
intake centerline: 109

next is the 288HR
Duration @.006 288/292
advertised duration 236/242
lift .52/.54
lsa 110
intake centerline 106

now for the questions: 1) why is it that the 288 is referred to as a bigger cam but it actually has lower lift numbers? is it because the longer duration 2) how is is the cam with the longer duration and tighter LSA is emissions legal but the 280 isn't? And finally 3) by comparing these specs isn't it basically that the 280 would produce more flow just at a lower RPM due to less overlap and therefore be more ideal for a TPI set up where as the 288 with it's tight LSA and increased overlap hurt the low end but be great for something like a mini ram or HSR with the upper RPM potential?

 

i don't think either cam could be emissions legal. advertised duration is always higher than duration at .050". so the 288hr cam advertised duration is 288/292, duration @ .050 is 236/242. lsa determines the length of the power band, centerline determines how early or late it starts.

 

the 288 IS emissions legal C.A.R.B. E.O. #D-279-4. so would having an earlier or later intake centerline move the powerband down>

 

Two things

1. Dont you still have to pass a sniffer test? I dont have to worry about that stuff where I am, but I figure that's what he meant. It'll be hard to get it to blow clean.

2. Why not go with newer grind? Like the xtreme energy or Lunati voodoo cams?

 

Here are the 2 cams side by side...

280
Cam has an Overlap of 58.00 degrees and has in Intake Duration of 280.00 degrees.
The Exhaust Duration is 288.00 degrees.
The Inlet Cam has an Installed Centerline of 109.00 degrees ATDC.
The exhaust cam has an Installed Centerline of 117.00 degrees BTDC.



288
Your cam has an Overlap of 71.00 degrees and has in Intake Duration of 288.00 degrees.
The Exhaust Duration is 294.00 degrees.
The Inlet Cam has an Installed Centerline of 106.00 degrees ATDC.
The exhaust cam has an Installed Centerline of 114.00 degrees BTDC.

I assume the 288 is bigger cause its has 71 degrees overlap vs the 58 degrees that the 280 has....

As per the #3 question... Smaller LSA Moves Torque to Lower RPM where as Larger LSA Raises Torque to Higher RPM.... Heres the link that lists what is affected by LSA.... http://www.compcams.com/Technical/FAQ/LSAproperties.asp

Some more info... Overlap is calculated by taking Intake opening at # BTDC and the Exhaust closing at # ATDC... So as per the 280... The Intake opens at 31 BTDC and the Exhaust closes at 27 ATDC... Add the 2... you get 58 degrees overlap.. Just though id throw that out there...Hope it helps a little...

 

i'm not sure if you are aware that the 288hr is a hydraulic roller and the 280xfi is a hydraulic flat tappet?