Batass

Let's say a 224/228 cam in an ls2. How much of a power difference would there be dropping to 550 lift instead of 600 or 612? I'm wondering how much of a sacrifice there would be to gain valvespring life/running cheaper factory springs. I dont know the advertised duration, so I don't know how aggressive the ramps are but either BTR or TSP most likely.

G Atsma

There would be a torque loss over the whole rev range. How much is anyone's guess.

Batass

Any idea how much with stock 243 heads?

99 Black Bird T/A

iTrader: (4)

Long post - sorry

Without a cam doctor the profile of the cam lobes in question and overlaying them its a guess in my opinion.

For example we had the cam doctor lobe profile for a very aggressive Morgan 224/224 .578/.578 lift cam. We had the cam lobe profile for my Comp Cams XER 224/224 .581/.581 lift cam.

Just looking at lift numbers the difference appears to be .003 which wouldn't be much difference.

Overlaying the two lobe profiles show the XER cam had more than 1 percent cam lobe area. It was clear the XER was way more aggressive and more powerful than just .003 more lift would indicate.

looking at how aggressive the lobe are would probably tell one far mote than the lift numbers.

Rough rule of thumb:

One can get an ideal of the cam lobes by looking at the advertised duration at .006 and subtracting the advertised duration at .050

The lower the number the more aggressive the lobe the higher the number the less aggressive.

Difference in lift between two cams below is .013 but only a small part of the story.

224 XER cam lobe with .581 lift advertised duration at .006 lift as 273 degrees. The advertised duration at .050 lift is 224.

273 - 224 = 49

49 is very aggressive

The old XE 224 cam with .568 lift was advertised at .006 lift s 277 degrees. The advertised duration at .050 lift is 224.

277 - 224 = 53

53 is aggressive

Just looking at .581 lift vs .568 lift doesn't begin to tell the difference in these two cams.


Regarding spring life todays great quality springs can go ~75,000 miles or so when properly match with some of the roughly .625 lift cams.


Ok guess time .550 lift vs .610 or so lift depending on the cylinder heads and intake manifold probably between 10 to 25 whp

DUSTYWS6

I would guess 15 rwhp, probably close to what someone would gain by going from 1.7 to 1.8 ratio rocker arms.

wannafbody

iTrader: (2)

I just saw someone on facebook changed his double springs out at 50,000 miles and they were still in good shape. A couple people here have gotten similar mileage.
So, I wouldn't be afraid to run the higher lift cam.

76dimepc

I got a cam Ground at isky for my 408 stroker stock ls3 heads 11.1 compression he gave 224 236 578 in 598 exh 112 lsa when I asked about more lift he said it wouldn’t make that much of a difference with the stick heads because they flow at about there max cfm in that area any more lift would net negligible results

wannafbody

iTrader: (2)

^ That's a pretty mild cam for a 408.

Batass

That's what I would think. Idk why I see so many "stage 1 and 2" cams with over 600 lift. I was told by a cam guy that I need to check my valves at 40-60k miles......
I just want 570 lift and want it to go 75k without pulling the heads off.....

76dimepc

yeah I want this one too last for a while it won’t be a daily driver but I do want to be able to hit the road sometimes

Batass

I figured. I've been looking at advertised duration and comparing them to .050.
The ls6 cam is 270/277 204/218. That's 66 and 59. I believe the ls6 was good for 100k? So 55 should be pretty good, sticking with 550 lift. I know there is more to it than that, but I'm betting the factory had pretty smooth lobes. So if I increase the adv duration a bit I should be able to go up to 570 lift and be a good compromise.
Trying to get a soft lobe, make good use of the 243 heads AND keep overlap low.....sigh.

SoCalDave

If you have stock heads as long as your cam is at least .500 lift and over you'll get the benefit of the flow from 243 heads. I stayed with lift of .515 intake, .522 exhaust since I drive my car all the time and don't want to think about changing springs anytime soon. My 799 heads are mildly modified and the low lift works well with my heads and the rest of my combo; really my problem right now is putting the power to the ground because I have major traction problems every time I put the "hammer" down, but it's fun.

Enigma540

Total lift isn't always "just about valve lift". Many times it's about creating more time to slow the valve down without inducing instability in the system. Also, say a head stalls at .550 lift.......by taking the valve up to say .625 or so, you can keep it in its peak flow area longer AND avoid harmful harmonics and instability in the system. Whereas if you were to take it only to .550 lift, then try to stop it, roll it over the nose, and start closing it again to fast you'd have horrible jerk values. Higher than necessary lift is often a better way to get good "area under the curve" without resorting to unstable velocity/acceleration values.

Batass

That's right, I forgot the duration for the rest of the lobe is much more than max lift.

99 Black Bird T/A

iTrader: (4)

I think one can get a cam lobe that's as a Comp Cam XE lobe. Those are 53 when subtracting.050 duration from advertised duration and still get ~ 100,000 miles with proper maintenance.

Definitely understand not wanting to deal with much valve train maintenance.

However valve seals often need attention even in stock engines wtc

FWIW i ran a nasty 49 ramp rate XER lobe cam for 130,000 miles with a couple of valve spring changes and new retainers and valve seals. Even having a shop do new springs, retainers & valve seals once wasn't too bad $700. Another spring only refresh was $400

SoCalDave

I read that as well that Comp Cams XE lobe is easy enough on the valvetrain to allow you to do minimal maintenance and be fine. I would recommend the XE lobe for anyone like me that drives their car many miles or doesn't have the time to tinker with their car on a regular schedule.

tsquared38016

iTrader: (8)

Here is a decent link to a guy that breaks down the technical into understandable. Start with what is your max air flow for your heads and what is the point of diminishing returns.

76dimepc

yeah that’s how I felt lookin at other builds but he insisted that I would have a wide power band good torque and it would work with my 2800 stall it’s in my 76 c10 with 4:10s not lookin to race just want good torque and what not

68Formula

Should still be enough duration to keep pulling past 6k even in a 408. If you want torque, that thing will be a beast.

Bspeck82

Depends on heads. If heads flow well up to .600 from .550 then there will be gains. If airflow remains the same or drops them no you wont gain power. On most ls2 heads I seriously doubt there will be gains from 550 to 600