Airwolf

iTrader: (2)

Which is better for our engine, higher lift or longer duration, both within reason. Another words, which will make better numbers (top end), a 224/228 .590/.590 or a 228/232 .580/.580? How would low end torque compare with these?

zracer28

iTrader: (1)

All things being equal I'd say they'd be real close. The 228/232 might have slightly higher peak numbers later in the rpm. I could be wrong though
The 224/228 would probably have better low end.

Someone correct me if i'm wrong

Cal

iTrader: (1)

I would expect the longer duration to add more power than the added lift.

C5 Purple Haze

I agree, however added duration will have a greater negative effect on street manners than added lift.

CATCH ME

iTrader: (1)

i would think that JRP's signature's cam guide would have some answers

blkZ28spt

My understanding is duration>lift on stock heads, with lift having a larger impact when you go with aftermarket heads. (but still less than duration)

Kraest

iTrader: (3)

Very Simply Put:
The longer you hold the valve open, the more mixture is going to come in. The lift isn't nearly as big an issue.

That's why you see cams with 260/270 duration @ .050 and .500 lift, but never see cams with 190/200 duration @ .050 and .900 lift.

It's also why stock eliminator cars run 10s under .500 lift, but use massive duration.


Mike

XTrooper

No question about it. The longer duration of Cam B is going to mean more than the .010" of lift of Cam A.

Airwolf

iTrader: (2)

OK, one more twist to this.. Which cam would be less stressful on springs, the greater lift or the longer open?

blkZ28spt

Stress on the springs depends mostly on two things: Lift and ramp rates. Lower duration with aggressive ramp rates is harder on springs than long durations with lower ramp rates. Higher lift is also harder on springs. The GM ASA cam is something like 226/236 .525/.525 and can be run indefinately with LS6 springs, while a TR224 (224/224 .581/.581, or .563/.563, I forget) needs a stronger spring because it has more aggressive ramp rates.

Beast96Z

iTrader: (21)

Valve lift is usaully a bi-product of the harshness of the lobe. Big durations with low lift tend to be slower ramp rates, whereas the low duration big lift cams tend to be very harsh ramps. It's not the case for all cams, but holds true to 95% of the cams used in LS-1's.

ChucksZ06

iTrader: (9)

The differences between the two cams is really too small to compare lift and duration...your only talking .017 lift at the valve with 1.7 rockers. That is less than the clearance for a solid cam.

ssheets

iTrader: (1)

Ah it would be so simple to reduce all the colors of the rainbow to just black and white.

People spend careers designing cam profiles trying to balance peak power and while retaining power under the curve. To ask such an over simplified question is an adminition of your lack of understanding. I don't mean this malicously, just factually. Study up on cams and the more you learn the more complex your questions will become.

This is MHO, I know enough to know not to answer such questions.

Airwolf

iTrader: (2)

I admit my lack of knowledge freely! I have looked over posted cam articles and spoke with people in the know, and the only answer I seem to get is "flavor of the time", meaning some times lift seems to be the "IN" thing (as I believe it is now) and other times duration. I know longer duration will hurt idle and low end power, but I also wonder why a stock head set would want to push open valves to .600 or more if duration can "almost" do the same. Seems like our springs would be much happeir, just our tuner may have to do a better job and NOT rely on plug-n-play tunes for $400 a pop. Again, I am not saying to go nuts, meaning close to 300 durations (that is nuts), but a year or two ago it would have been nuts to suggest over .600 lifts, but here we are....

ssheets

iTrader: (1)

Well first off, thanks for taking my comment as it was intended. I am truly a student, not the teacher here.

I do know a very good teacher and he has spent hours of his time trying to help me understand the dynamics involved.

A few things: One, you can't seperate lift from duration. Lift is in many ways an affect of duration or visa versa. If you look at a cam profile you'll understand that for a given slope you will acheive more lift if the event starts sooner and ends later. That's why so much work goes into profile or lobe design. This is limitied by shear physics and the limitations of the valve train geometry. You can only push a lifter so hard before you're pushing it sideways.

2nd, flow is a product of port design, valvetrain affect, valve diameter and the valve job itself (I'm sure I left out a few things) Flow is really more cirtical or productive right as the valve opens. The valve spends very little time at max lift and therefore this number is not as relevant as it is just a measurement. Larger valves will give much better flow as the surface area of the valve diameter increases by the multiple of 3.14 times the increase in diameter. The key is to produce power under the curve.


Well good luck and I'll be posting soon with results of my H/C swap going to 11:1 CR with 2.02" intakes and an F14 cam (232/234 .598"/.598")

Airwolf

iTrader: (2)

SS,
Drop me an IM when your mods are done. Best of luck with the numbers! They should be very nice. Cheers

ssheets

iTrader: (1)

Thanks and same goes to you...I just hope I've chosen the right teacher