Matt D

iTrader: (49)

I wanted to start this thread as this has been the new talk in the LS1 world. When the XE-R cams came out there was so much hype about how great they were, but now that the LSK cams are here, they seem to be the cam to run instead. I would like those who know cams very well to give pros & cons for both types of cams. I myself have a MS3 with stock heads, and only put down 385hp @ 6600 and 321tq @ 5100, but run very well at the track. Let me know what you guys think as far as the two cam types. Thanks.

Matt

SStrokerAce

iTrader: (2)

Do you want to discuss the difference in the lobes and what that difference means in terms of power, stability, other valvetrain parts etc...? Make this a real Advanced Tech type thread. I'm on the wrong computer to do that now.

Bret

Matt D

iTrader: (49)

Yes, I would like the thread to include such information as you have stated, as well as valve events, dynamic compression, duration, LSA, etc, and what plays the role in horsepower and torque for the two.

I see a lot of people saying, "which heads for this cam", but in all actuality, shouldn't you be picking a cam by which heads you have?

SStrokerAce

iTrader: (2)

The valve events, DCR and LSA don't have anything to do with the lobes themselves.

The differences in the lobes will provide changes in HP and TQ.

One thing the LSK lobes provide is more lift, which in some of the situations that it's used in aren't really needed if the cylinder heads are up to the task. Meaning if you have a better cylinder head you would gain less with the LSK lobe over the XE-R since the better head doesn't need as much curtain area to make the same power.

This actually gets into a lot of discussion about lobe area, so we would have to look at examples with equal lobe area and equal traditional specs as well. Basically it's a study in understanding the differences between any two cam lobes and what that difference translates to in a certain application.

Bret

DAPSUPRSLO

iTrader: (14)

In a very general sense I think you could say that the more lobe area in a same advertised duration value will net you more power in cylinder heads and intakes that most here are concerned with, given that your valve train can control the lobe. If someone could show us a cam doctor of similar advertised duration xe-r lobe and then a cam doctor of the lsk lobe you could see the difference in the higher lift regions where if I had to guess the lsk lobe really takes off!

DavidNJ

Bret, this statement seems backwards to me. If you have a head that stalls at high lift, the extra lift won't help, may even hurt. The extra duration at .200 (.340 at the valve) would help though. With a head that flowed well right past the .630-.660 LSK list, I would have thought the lobe would have had the most advantage.

I would have thought the big problem would be the small 1.29" valve springs used on most LSx engines. I would have thought that lobe (and the similar but smaller base circle XFIs) would like a 1.55+ spring like the 26055 or 26095 beehives would have worked better.

ThirdGenLS1

iTrader: (11)

A LSK lobe will be one degree smaller at .06 compared to a XE-R, the same at .050, and 4 degrees bigger at .200.

Justin

SStrokerAce

iTrader: (2)

Yes and no... depends on how you get there. You can have a lobe with a very tame profile and a lot of lobe lift, a lobe with an aggressive profile and less lobe lift and a very aggressive profile and a lot of lift.

For example

Adv - .050" - .200" - Max - Lobe Area

304 - 244 - 161 - .383 - 30.8
293 - 244 - 165 - .360 - 30.6
293 - 243 - 168 - .384 - 32.0

Now in this example the top lobe is very tame and has a lot of lift, while the middle lobe has the same area but with less lift and more area from .050"-.450" valve lift and less area above .450". Even though they have the same area the tamer lobe will be easier to control and has more area where it's usefull, which is the high lift area.

Now compare the first and thrid lobes. The 3rd has more area, but it is also a lot more aggressive off and on the base circle and has a lot more .200" duration. This lobe will have more area from around .075" valve lift on up, but it also is much more aggressive and will have high velocities and accelerations off and on the seat and over the nose, which means you need either less mass or more spring pressure and rate to control the valve.

Now how is all of this going to change the power? Well that's where valve control comes into the equation. The 1st and 3rd lobes are going to give you different results depending on the valvespring package and RPM. Say you are using a spring with 140lbs on the seat and 300 open. The 3rd lobe will give you more average TQ till about 6400rpm if you are only turning the motor that fast. If you are going higher the 1st lobe will get you more and allow you to turn the motor another 600-800rpm higher, which will give you more average TQ. IMHO if I can get the same power (which would be the case here) and get more RPM, which will also bring up my average numbers, I get to use more gear or more tire so I can make the car get down the track or too the next corner quicker. You could always go the expensive route, and throw better springs, ti retainers and valve to get the valve control back and maybe get a slight average TQ advantage, but that's a big maybe.

Bret

SStrokerAce

iTrader: (2)

David, I don't use heads that stall at high lift. This comes more into play on motors that actually need all of this curtain area, like high RPM big cube motors. You can only put so much valve in a motor the only other thing to do is throw lift at it and then your heads better really be on their game.

The problem with more spring is more mass comes with it, which compounds the problem. If you cure that or compensate with even more spring pressure you need more stiffness in the system as well.

Bret

DavidNJ

First, those are low mass beehive springs, in contrast to the double springs with dampers used in most LSx XER and LSK setups (such as a Comp 921 or seemingly ever popular Rev 8890).

I would imagine virtually all LSx heads would work better with .650 lift vs .600 lift.

DAPSUPRSLO

iTrader: (14)

Yep, which is why I said in the general sense. One thing that has not been mentioned here is the dwell time that is increased with a more agressive lobe, that is the more agressive lobe will have more duration at all lift points (in general) which allows more volumetric effeciency/more BMEP to occur in general. The more head/intake limited you are usually the better the motor responds to more duration, be it in advertised, .050, or .200, etc. duration it seems. But like pointed out earleir, it is all dependent on your vavletrain's ability to control the agressive opening/closing induced by these agressive lobes in the rpm range that you seak. If you are able to control the valve at whatever rpm you are concerned with, the more agressive lobe almost always wins in power output! The only situation I could see the inverse happening (once again, granted that the valve train can control things) is when you have a cylinder head and intake that supllies so much air that more cam does nothing but bleed off BMEP. The ls7 would be a good example here, the cam in that motor is rediculous small for a 427 and the motor goes to 7000, the heads are responsible for that for sure!

SStrokerAce

iTrader: (2)

As I said, the more aggressive lobe doesn't always win out in TQ output even when you do control it, i've seen it happen. BTW I've never heard of bleeding off BMEP with not enough cam??? BMEP=TQ

FWIW a 347 that wants a HP peak at 7000rpm with a 2.00" valve is fine with .600" of valve lift. A little more lift would help as well, but this is a much more demanding setup than any of these guys here run. Most want the HP peak lower and have more valve diameter. If you added .050" to the valve diameter and took 400rpm off the HP peak you wouldn't need more than .600" lift.

Bret

DAPSUPRSLO

iTrader: (14)

In those instances was it possible that a harmonic in the valve train was taking over? As you know sometimes they can present some very hard to find holes in the power curve.

I've never heard of bleeding off BMEP with not enough cam either, which is why I never said that I did however say that maybe too much cam could bleed BMEP off (from agressiveness or just simply large duration)

SStrokerAce

iTrader: (2)

Nope it wasn't harmonics because that happens at a certain RPM. What I am talking about is not seeing a jump in the TQ curve due to the larger area cam lobes.

I'm talking about bleeding of BMEP.... BMEP = TQ per cube basically so how can you "bleed" that off? It's just bad engine slang since it doesn't make sense.

As for cool motor sayings though... Darrin Morgan said "come on the pipe" the other day when he was talking about a NA motor picking up TQ due to the induction tuning working in the RPM range and that is about the most fitting slang for describing what is happening in a motor I've heard yet.

Bret

DavidNJ

To late an IVC causes a loss of compression until sufficient intake momenturm is achieved. Making a small engine rev has that problem. VTEC is one cure.

Who said anything about BMEP? Isn't the XER lobe associated with Hillary Clinton's presidential campaign?

There is nothing magical with .5, .55, .6, or .65" of lift. The limitations are what the valvetrain can bear with the prescribed duty cycle. Change a 150k emissions cycle with limited maintenance and low cost parts to a street/strip car with constant maintence and more expensive parts a lot is possible.

Net, after the fear of problems wears off, LSKs will probably replace XERs for all LSx aftermarket applications.

SStrokerAce

iTrader: (2)

Problem is I dont think that the problems will wear off since we already have some nice clean wire springs out there now, and anything else will be MUCH more expensive and the average guy/gal doesn't want to pay $500 a set of springs. The difference between a set of throw down heads with a good street hyd roller spring setup and a high RPM high lift solid roller setup can easily be $600-$800+, most guys can't stomache that.

Bret

s346k

iTrader: (4)

i'd like to see a back to back comparison of a cam with the same specs...ground on xe-r lobes and then lsk lobes. is it possible that just the lobes themselves could be worth 5-10 peak rwhp on stock heads/compression? or even more important...a few hundeds and/or tenth(s) at the track? as the lsk lobes would theoretically make more power virtually everywhere in the band. i wonder what kind of valve bounce effect is caused by the lsk lobes vs xe-r...closing the valve faster would cause more, correct? what kind of effect would that have on power output? when will we know the ramps are TOO aggressive?

racer7088

I have not seen the LSK make more power than the XER yet but I am sure it could if you had light parts and good springs that were happy with it.

When we have real data I will certainly share it but some people had some bad results early on so many won't use the LSK yet. I have and one time is was good and one time it wasn't.

DAPSUPRSLO

iTrader: (14)

Oh, ok, just throwing the harmonics possibility out there. I don't understand what's so hard to understand about "bleeding" the BMEP off but to each his own. Maybe my internet warrioring skills need some work, lol. For clarrification purposes I mean that by holding the valve open longer or opening it earlier at whatever point in the lift range dictated by the lobe profile you may be allowing part of the mixture to escape be it through the exhaust or back into the intake which is what I mean by bleeding it off, which is what i'd assume is happening in the instance of not picking up any more power with a more agressive lobe Bret. Obviously there is a point in which more duration at whatever lift point is not doing you any good cause the inertial filling, wave tuning, whatever fill is done in that rpm point, sort of like what DavidNJ is saying.

Ric

Thanks to all for the info. I'm thinking out a good non-everyone-runs-it-so-it-has-to-be-good cam, kinda like Patrick G's new cam.

I'm no expert on lobes by any measure, but I am curious as to how the LSK and XER got their nomenclatures... are they brand names, abbreviations, what exactly makes them what they are?