Ron_Stoppable

iTrader: (1)

I have a 5.3 with a 228r Comp Cam. The specs are .588 on both valves with 277 duration. Just wondering what the higher duration does? Sorry if that sounds stupid

KCS

iTrader: (20)

In a nutshell, it keeps the valves open longer to fill or evacuate the cylinders better. There is a lot more to it, which you can find in the "stickies" at the top of the section.

Start with this CAM GUIDE for starters.

96capricemgr

iTrader: (1)

Also try to understand cam durations can be specified at several different lift values.

Ron_Stoppable

iTrader: (1)

So since mine is 277 on both valves does it make a difference in sound/lope. Is it beneficial to me since its so high?

HCI2000SS

iTrader: (2)

Well that depends on what you define as beneficial, and yes both duration and LSA will determine the overlap thus sound that you will have. Basically more duration equals more of a rougher idle

badazz81z28

iTrader: (6)

277 duration??

The 228R has a duration of 228/228 @.050" lift.

bww3588

iTrader: (49)

277 is advertised. 228 is at .050 lifter rise.

soundengineer

iTrader: (16)

in general, the more duration you have(without changing lobe separation) will give you a lopier/chopier idle

you can counter act that a little bit by making the lobe separation angle wider....to an extent... there is a point where it will start to hurt power and torque

all of these things are better explained by valve events and overlap...
which is a completely more technical discussion, that I feel is probably not what needs to happen here...

but basically, Larger Durations usually mean more peak power with the sacrifice of low end torque
larger durations usually mean larger overlap, which means more lope

Lift and duration usually follow each other to some extent to keep a certain lobe profile which will be not too aggressive and not too slow to both make power and make it less traumatic on valve springs


to put it all in perspective
a 224 cam is usually under .600 lift and most versions have little or no overlap @.050
and it sounds reasonably tame and almost stock to some people


my personal cam is a 252/274 .646/.646 113+4 and I have 37* of overlap....
with total duration of 303/328 @.006

definitely not stock sounding....it sounds more like the apocalypse is happening....