'02SOMz28

iTrader: (1)

x2 im going to take my 231/237 out and get a Pat G cam

redsap05

I would go with either a pat g/eps cam or the lsl cams. The comp lsr line of cams all use the lsl lobes. I would run away from lsk lobes ( texas speed) and xer's as well. Reason being is that stuff that aggresive is simply not needed and down the road should you decide to buy a nice set of heads like trick flow or afr you want a less aggresive lobe when you have nice head with excelent low and mid flow numbers. Lsl lobes have been kicking *** with trick flow, afr and even l92 heads.

SOMbitch

iTrader: (8)

More agressive in this case does not necessarily mean harder on parts unless I am misunderstanding something....

From my understanding the LSL (and similiar and EPS lobes) are slower on and off the seat and have less jerk and are therefore easier on seats and easier to maintain valvetrain control... I believe they achieve this despite the higher lift because the lobes are fatter...

This kinda explains it....>>> http://www.engpwrsys.com/tech-notes/cam-design.html

bozzhawg

Ok, I don't need the interweb for this discusion but here goes....

Lets go back in history, for years, Comp has run symetrical lobes and when they were presented with the option to run assymetrical lobes especially with fast opening rates and slower close they declined.... now this was around the late 70's and who was the cam designer when they had a 1 room shop... UD Harold, and in 1980 he took his cam designs and assymestrical fast open/slow close technology and started Ultradyne cams... 95% of all of UD's designs are assymetrical with a fast open, and slow close ramp rates... Why the slower closing ramp rates, to lay the cam gently on the seat and not slam it down... easier on the valve train..... less harmonics from the valve slaming shut and when you accelerate and decelerate, less strain...

Now lets go back in history some more, remember when all the guys complained about the XER and XFI lobes etc....? The ramp rates and lobe design, but do not think for one second that the LSL lobe is the savior... You will be mistaken and they are tame lobes... The LSL actually has a faster ramp on both sides of the lobe than the XFI...... No bullshit... The LSL is actually a lobe designed for race applications, not a daily driver or car that will see a lot of highway miles unless you like changing your valve springs out every 10-15,000 miles, but you know how it goes, some guys like to push it to the edge... Every LSL lobed car I have heard or seen, has a distinct sewing machine sound and you can hear the valvetrain noise.... Here is a quote directly from someone I know at Comp..."The XFI are a fast open and fast close but don't have the same short seat to seat timing as the LSL and this makes the XFI more streetable".. I think you are missing or confusing shorter seat timing for slower on and off seat ..... what they mean is the LSL lobe is a very agressive lobe for the seat-seat timing given whether it be advertised duration or duration at .050 etc.....plus the seat-seat duration degree will be lower for a quicker opening cam vs a slower opening cam period.....

look at the degrees of durations at .050, .100, .200, .300, and .400 and that can help you with an understanding of the lobes agrressiveness and some of the potential characteristics of the profile...... designing cams with different degrees of duration along the lobe or as you call it (fatter) is not new technology bro.... been around since before 1980......


Here is some more info for you:
So as you can see, these are race cam lobe profiles, not intended to truly be in daily drivers........

the difference is
LSK faster open/faster close....
LSL fast open/slower than LSK close......

I don't know all of the EPS ramp rates and lobe profiles 100% but I do not believe they are LSL equivical.....

The EPS stuff they finally figured out after 10 years is actually not new and inovative... this technology has been out before 1980..... Just buy an old Ultradyne cam and I bet they are almost identical side by side....

SOMbitch

iTrader: (8)

Very good points Bozz and just the response I was looking for... I will look at my lift rates from .100-.600 to get a better picture. I understand what you are saying about shorter seat times. Word on the streets though is these cams make great power and are easy on parts(yes I understand that is a relative term). As a side note my EPS cam on this motor is almost dead quiet and quieter than my old XFI/X-ER custom cam on my 346. Both had the same YT-UL's And when Geoff speced my cam I told him parts longevity was a priority so my 238/250 cam has a soft marine exhaust lobe @ .613 lift.

And you said the LSL's were easier (slower) on the seat so isn't that a positive????

I know everything is a tradeoff so just trying to understand it all.... Thanks for sharing your knowledge...

Edit: Stability is also mentioned as an advantage with these cams and this is often a problem with these motors...Maybe the short valve seat time improves valve control and keeps the valve from bouncing off the seat with less than ideal spring pressure?????

Neumonic2002

Good info, thanks for posting!

bozzhawg

I should ve been more careful of how I said slower? slower than what? Slower in terms or reference to a LSK lobe or lobes in its same family or class..... The LSK lobe is really and all out race lobe, so yes it maybe slower with less lift than an LSK lobe but not necessarily slower in correlation to some other less aggressive lobes.... Its like hot sauce, yes it may not be Super Tabasco hot , but its still hot sauce thats hot......lol

You are correct, but don't quote me on the EPS lobes I do not, and have not done any personal examination of the EPS stuff but from reading their info, it sounds like they have a fast opening but slower close ramp rate which is easier on the valve train, and not closing the valve at an accelerated rate to be harsh on the seat..... ex: they may open at a ramp rate of 15 but close at rate of 7 vs some cams that open at 15 and close at 15.......A lot of fast action cams that generally have a fast opening and fast closing ramp rates run into issues of valve bounce... The cure often applied? stiffer valvetrain parts... etc. But the stress is still applied to the parts... .....This can be debated, but some of the control that you will experience is more due to the increase in required spring rates or simple terms stronger stiffer springs required with these lobes. Not to take away from the design development done on these lobes.... But to prove my point, take these lobes and set them up with say a 918's or other springs with lower spring rates and stock pushrods, stock valvetrain, head parts vs aftermarket pushrods, some partiot golds,extremes,pac's, 926's,PSI's etc.... You see? now which version should have better control? and Yes some guys skimp on the valvetrain and do not match the correct parts and get away with it, but that does not make it right.....Yes the camshaft design does dictate some of the responsibility of stability, but at this point, the other valvetrain parts help to maintain the stability.... So, its about the entire combination of parts to make it work properly....


Whether loud or quite valve train?
What you are hearing are the harmonics waves throughout the valvetrain dictated by the camshaft... remember the camshaft is the brain, and it tells the valves what to do in a simple explanation...... the valvetrain is not an independent variable or force in its own right..... Thats why, I have always preached, you build power from your topend or top parts heads,intake,carb,efi, cam, etc....

There are always tradeoffs and as performance seekers, we are placed with the struggle of street or strip........ as you go one way or another, you tradeoff or compromise a certain trait or result..... But I think most need to realistic with our goals and intentions.... Max effort or avg power? low-mid range or topend? Do you want power from idle-4500 or 4500-6500? Do I want a engine I have to rev to 4500 before the power comes on or do I want the power early? Can I live with the great low-mid range power or do I want power throughout the entire powerband?

SOMbitch

iTrader: (8)

Good post Bozz. Yeah that all makes good sense to me. Happy with my EPS lobes but as you explain things they are more agressive than I originally thought. I will look at my Cam Doctor report and calculate the lobe intensity......should have already done that anyway. IIRC my old X-ER/XFI cam lobes were around 49 or 50...

bozzhawg

Yelp, the problem with comp is being able to get the durations at .100, .400 etc.... If I were you to even clearify my info call Comp..... Remember a couple years back when Pat G did a test with the LSK lobes? What did alot of people do run out and buy the LSK lobes, but how many still have the LSK lobes in a DD without changing springs out or some valvetrain issues.... I am not talking about a weekend warrior, I am talking about a true 10-20K a year daily car..... I am not knocking the Comp lobes they are good for the right setup, thats why they have different families of lobes for different driving and performance intentions.

But just check the info out to keep me honest....lol

ringram

Yep, right from comp's catalog

"COMP Cams® LSR™ Camshafts are a new line-up of hydraulic roller camshafts featuring
our most modern lobe designs for popular GM LS engines. Designed specifically for radical street performance and all-out race
applications, these aggressive profile cams take advantage of today’s newer and better fl owing aftermarket cylinder heads."

Didnt stop me using one though. I think I might need some nice new springs in a year or two. Maybe some lightweight lifters too.

SOMbitch

iTrader: (8)

Yeah I just checked my Cam Doctor report. If you agree lobe intensity is measured by subtracting .050 duration from .020 duration my lobe intensity is (rounded off) I=27/E=29...That is a DAMN aggressive street lobe but I have to say my graph is nice and linear and gives no hint of valvetrain issues..... actually a little smoother than my XFI/X-ER graph with the same heads/springs....

bozzhawg

Yelp, I bet with the EPS, fast open/ slower close, 0 jerk should be easier on the seats and valve train harmonics......

ringram: I like em too, I just wanted to explain the pro's and the con's, every lobe design has them....

Advanced Induction

iTrader: (2)

Indeed. As guys have pointed out, "aggressiveness" not only varies from lobe family to family, but also between various areas of the individual lobe. That is compounded by the fact that often times not all lobes in the family exhibit equivalent velocity/accels/jerk/etc, have slightly different operating ranges, etc. That said, as has been alluded to, all of them can be made to run reliably if the rest of the VT is appropriately selected, installed, and adjusted.

Often we get questions regarding the differences between the common lobe families, and I'd actually made an XER/LSK/LSL comparison graph for one customer in the past between 3 lobes, all within 3-6deg duration.

Late to the party, but someone may glean something from it.



Good luck!

-Phil

EDIT: If the image is too large & forcing everyone to scroll, let me know & I'll edit/link it.

bozzhawg

Classic thread in the making, Damn AI, you hit it on the nail......


Very good info being thrown around here...... especially the graph showing the intensity or measurements at different durations or degrees along the lobes.... classic....

AI: Your late to the party but you brought some good wine....lol

Neumonic2002

Great information, extremely helpful in understanding the differences in the lobes!

rem308winvtr

iTrader: (24)

Texas Speed LS3 231/236 .641"/615" 113 LSa

Neumonic2002

Is this your choice?

Can you share some input?

Neumonic2002

Looking at the fantastic data provided I think I will go with a happy medium and have a custom cam ground, the specs will look like this:

231 .617 LSL intake lobe and a 236 .607 XFI exhaust lobe

Thanks for everyones input!

John

Advanced Induction

iTrader: (2)

Glad it helped.

Neumonic2002

well after a lengthy discussion with Brian from Comp at the LSX shootout yesterday it looks like I am back to where I started lol.

He didn't like the LSL/XFI combo so I will stick with the Spin cam

231 LSL/234 XER, cam will make very nice power and have very good driveability.