ChrisB

Not sure what you mean by that - if you mean you are using comp's valve events, then yes - of course, I never said those wouldn't work. My comment was in reference to the formula you posted - it most definitely will *not* work for assymetrical lobes. See below

Say we have a lobe with the following events

IVO 0 ATDC
IVC 0 BTDC
ICL 100 Degrees

So we have 180 degrees of duration, and a ICL of 100 degrees (assymetrical).

Using your formula in reverse we would get

IVO = (180/2) - 100
or
IVO = -10 degrees

which is obviously different that what it should be. Your deviation is going to be directly related to your deviation from symmetrical with this formula!



Also I am still interested in more specifics in how you determine an appropriate setup - not that I disagree with much of what is said, but instead of saying "take the intake, exhaust, etc. into account" I think it would be more interesting to say something like "I shoot for a 2nd order harmonic at these runner links, which with a yyy length intake path occurse at zzzz rpm, to support peak VE at that rpm we need xxx degrees, with valve events at a and b".

Again, I just think we can get a better discussion going if we talk about the reasons behind choosing certain events!

Thanks again for your input,

93PONY

Chris,
A 180 degree duration cam with a 100 ICL WILL open at 10 btdc.
For the IVO to be 0 & the IVC to be 0 the ICL must be 90....not 100.

We're not talking about degreeing an asymmetrical lobe using the Intake centerline method here. We're using the .006 & .050 duration specs from Comp & setting the 'center of the lobe', not the theortical degree at which Peak lobe lift happens. Simply put, the 'center' of the .050 or .006 duration specs. This is the way Comp grinds these cams.

My posts are not intended to confuse anyone....& this is why I simplify what I'm saying so the average Joe can have a chance at understanding what I'm talking about.

LIL SS

iTrader: (9)

Sean, Is he putting the A4 back in it too. I'm sure that had a little to do with it as well

ChrisB

What definition are you using for ICL? To the best of my knowledge, the centerline of a lobe (intake or exhaust) is the point of max lift, located radially.

If you use that definition then the centerline can be wherever it is ground on the lobe.



But the ICL is NOT the "center of the lobe" - it is the point of peak lift. The ICL number you get from comp is measured this way also. If you use that value and assume it to be the "center of the lobe" then the numbers will be off also.

My cam card from comp *does* agree with your formula, but the cam-pro readout I got from comp (verify the cam) as well as the one I had done at GTP don't. The ICL was the same (on average), but the intake opening and closing were both about 2 degrees later. The comp card said
ivo -9
ivc 43
icl 116

while both cam-pro's agreed at roughly
ivo -7
ivc 45
icl 116

I just assumed the comp card wasn't being that precise, who knows.

But anyway, I will agree to disagree with you on that! I am still definitely interested in getting more in depth on the metrics for choosing a camshaft!

93PONY

Chris,
It's quite normal for the actual cam specs (from a cam dr or cam pro) to be different from the Cam card. We're talking about thousanths of an inch & 1-2 degrees in a 720 degree circle with a 55mm diameter. Variances from cam to cam with the same grind # & cam card is normal & expected. This is why one should always degree the camshaft....even if a cam pro printout came with the cam. There's still variances in timing chains & gears....
Anyway.. That's normal. I've seen cams off by as much as 6 degrees for the ICL. & 2-3 for a given lift point. Typically however, the .006 points are on the money. & since this is the start of the lobe, this is what really matters with relation to the ICL/ECL.

ChrisB

I'll let stand what I posted, otherwise it's just beating a dead horse - but on the camshaft issue -

when you spec a camshaft for a certain motor what kind of factors do you use?

black_knight

iTrader: (1)

93 pony, J-rod et all:

Hiya. Long time lurker, first time poster here.

I had a question about what you said earlier about the runner design for LS1's. You seemed to imply that becuase of this fixed length of the runners, the ideal powerband for the LS1 is set to, at most, the low 6000's at best. This seems to contradict a lot of what I've heard about people using the larger cams, like the g5x2, who have dynosheets showing peak power up in the 6700-6800 range.

Excuse my ignorance, but is this dependant on the intake that they are using? Does the ls6 intake feature differant runners? How about the new lsx?

Thanks

93PONY

Intake runners, exhaust runners (headers), head design, & cam design all affect the RPM band on a given shortblock.
Match all these parts up correctly & the motor will make serious power.
The larger the cam, the higher it'll want to peak. Mate one of these large cams up with an intake that can not peak that high & what you end up with is a comprimise. At the intake power peak the cam is not at it's most efficient (peak power), above that RPM the power curve tends to flatten out till the cam peaks. The curve from 6200rpm up is no where near as steep as the power curve from 4800-6200 (peak torque to peak HP with these 15 inch runner manifolds).
What I shoot for max power given the RPM capability of the entire combo.

Even though these setups make tremendous power, very few have tapped into the true capability of the LS1. These motor have the potential to dominate racing.
If a little N/A 302/306/308 H/C/I full weight mustang can hit 10.5's at 129mph... Imagine what the LS1 will be doing given 10 more years of aftermarket exposure.

black_knight

iTrader: (1)

Interesting. So is the runner length differant for ls6 intakes? For the lsx?

bigeller

iTrader: (2)

Much of this discussion seems to be over my head.. hah.. I was wondering what your take would be on the cam I've chosen for my setup JRod, 93 Pony or anyone else that wants to chime in.

I have an LQ9 Escalade engine in the Z28.. the bore and stroke is 4" x 3.62" The CR is 10:0.1 with the flat tops..
http://www.gm.com/automotive/gmpower...ehicle/lq9.htm

I picked the TSP 228R wuth the 3724 lobes.. It's a 228/228 .588/.588 lll LSA +4 The cam came +2 but we added +2 more for a total of 4* advance.. I used JRods excel sheet and came up with:
Intake Duration - ID 228
Exhaust Duration - ED 228
Lobe Center Angle - LSA 111
Intake Centerline - ICL 107
Intake Valve opens - IVO 7 BTDC (- indicates ATDC)
Intake Valve closes - IVC 41 ABDC
Exhaust Valve Opens - EVO 49 BBDC
Exhaust Valve Closes - EVC -1 ATDC (- indicates BTDC)
Exhaust Centerline - ECL 115
Overalap 6 degrees

Right now I'm running the stock #317 D port heads, but I have a set of SDPC LS6 CNC heads with the 70cc chambers waiting to go on.. BTW great article on the SDPC heads flowed at MTI vs their heads JRod.. I'm going to see what they'll do with stock valves and the 228R cam.. The heads are supposed to flow great up to .590 according to that article.. Sounds like a good match for my cam..

So how do you like my cam for an NA setup? Opinions?

Thanks
Michael

93PONY

bigeller,
I would retard that cam 4-5 degrees.

Also, It's not a bad thing to have a cam with higher lift then what the heads are capable of. If the heads stall out at .550 lift, I may throw in a cam with .590 lift. The stall actually helps atomize the air/fuel mixture. Plus you get more duration where the heads flow the best. However, I probably wouldn't throw that same .590 lift lobe in with heads that stall out at .500 lift.

bigeller

iTrader: (2)

What exactly would retarding the cam do for me and my setup? The car has been tuned to shift at 6600 and rev limit at 6900..

Thanks

93PONY

Retarding the cam will make more power across the entire RPM band. It won't move the RPM band up significantly. Shiftpoints should stay the same. The intake is the limiting factor, so retarding the cam won't have much affect on the RPM the combo peaks at.

You'll also get a smoother idle & drivability below 2K rpm.

black 2001Vette,Nightmare

Hi 93PONY. Like many others, that have been watching(reading)in the wings, during this discussion, I also, as a firsttime poster here, with very limited knowledge on internals would like to get your feedback on my new recently required head/cam application. Could you please critic my new set up?:

New 2002 LS6/LPE ported,polished/paper rolled heads w/the larger valves, and 11.0 to 1 cr...228-228/.588-.588/114+4 LSA, stock bottom end, Comp cams Hex adjust timing chain, LS6 intake, LGM original LT hdrs w/ merge collectors, and no cats.

Any comments whatsoever will be appreciated! Thanks in advance!
NIGHTMARE

black_knight

iTrader: (1)

"So is the runner length differant for ls6 intakes? For the lsx? "

I said that. Does anyone intend to answer?

93PONY

black knight, I do not know the actual runner length of the LSX intake. Both LS1 & LS6 are 15 inches.

Nightmare:
Sounds like a stout 400+RWHP combo. I'd have to say the only thing I'd do is retard the cam 4 degrees.

black 2001Vette,Nightmare

93PONY, thanks for the reply! It's funny you have said 400+rwhp...cause that's exactly what it dynoed!
The tuner who did my package has told me, that if it were not for the Vig converter and 3:73 gears, it would dyno 430rwhp...agree or disagree? He says that I'm losing close to 30 rwhp on the dyno due to these two mods.

Also 93PONY, how will the 4 degree retard make itself evident on the road?

I know I'm a bit off subject here, with this question, but at least my question won't give you a headache!

Thanks in advance for your expertise!
Nightmare

black_knight

iTrader: (1)

93Pony,

Thanks for the answer. The reason I asked is because you had said before:

"Due to runner length & the current lack of cost effective shorter runner intakes, the LS1 is limited to a 4800rpm torque peak....& thus 6200-6400rpm HP peak (due to the wave of the incoming intake aircharge as it bonces between the closed intake valve & open air plenum)."

I am basically asking if it is pointless to go with a cam that peaks higher than 6400 on an LS1 due to the fixed runner length. I understand that a bigger cam will peak higher; I also understand that it is possible for the cam to want to peak higher than the motor wants to. (something that I would think might happen soon enough, if not already with many ls1's)

Since you seem to be the only fellow who actually understands this conundrum, I figured I'd ask.

ChrisB

93Pony - what exactly are you looking at to determine that the camshafts in question should be retarded?

Assuming the lobes are the same one is a 111lsa while the other is a 114lsa - so if you retard them both 4 degrees as you suggest they are going to have different valve events (they will of course no matter what unless the cam is reground - I am just curious as to the reasoning behind retarding them both 4 degrees since they are different?)

bigeller

iTrader: (2)

Good point Chris.. It looks like the lobes are the same XE-Rs given the .588 lift.. Maybe it has something to do with my car having the 6.0, approximately 20 in^3 more??

I think it would be an interesting comparison between Nightmare's setup and mine.. I also have 3.73 gears and a vig stall.. My LS6 CNC heads are going on soon.. They are stock valve size and will flow around 300cfm from .500 to .600...

What kind of horsepower and torque will I put down..

93Pony, what effect will having my particular cam have in my 6.0 over the 5.7, roughly 20 cubes more assuming the same compression. I'm thinking more torque for sure..

Thanks for the great topic.