Unless the valvetrain had problems with deflection or float, or the head stalled, I don't see why more lift shouldn't produce more power. It is not only more maximum lift, it is more duration at virtually all lifts. Do your heads flow better at .300" than .400"? If not, that getting to .4" earlier should make it work better. Additionally, the mroe aggressive cam should allow equal area under the curve with lower duration off the seat. That should allow more compression.

In any case, hydraulic roller lifts are generally pretty lame, closer to solid flat tappet lifts. If a solid roller was being used, the LSK would be considered a very mild camshaft.

 

I agree with Brian.

 

This is “text book”, or should I say, “computer software” methodology. When I was first trying to get as much knowledge as I could, (10-12 years ago) I used as much software as I could get my hands on. Some of it was good, but a lot of it was bad. Most all computer software shows more power as you plug in more lift, while fine in theory, is not how it works in the real world. The cam and head work in combination to fill the cylinder with air. Lets say you graph the airflow requirements of an engine to make xxx HP @ xxxx RPM, this “airflow curve” would look like one big sine wave. If you could graph the airflow to the engine using the airflow of the head COMBINED with the cam lift and duration to yield one big “airflow curve”, I think you could then start to see how your combo matches up. It is my personal theory that anything beyond this is wasted mechanical energy or wasted airflow. I can attest that increases in airflow, even without increases in port volume, can yield diminishing returns. Increases in cam acceleration rate past what is needed is either squashing the lifter or simply slowing the velocity of air around the valve, I don’t know which. But I can tell you FOR SURE that I have seen faster ramp speed cams make less torque, less power and float the valves sooner. If you have a stock head with mediocre midlift airflow, then combine it with an LSK lobe, it may yield an “airflow curve” that is more closely matched to what the engine wants. Conversely, if you have a head that has very good midlift AND high lift airflow, you can use a cam with mediocre ramp speed and lift, but still make excellent power. I like the latter setup, a car that starts nice, idles nice, makes great ALL AROUND power and not just a peak number. Hope this helps.

 

Brian, you put a lot in that one large paragraph...let me see if I can break it out a bit.

Most computer software doesn't deal with the valve train issues. I haven't heard anyone say there was a 'compression' problem with LS1 lifters. Is there? Otherwise, with sufficiently light components, adequately stiff pushrods and rockers, and stiff enough springs, valve float or valvetrain deflection should be the problem. The actual lift in an LSK is really not that great...at least by solid tappet standards. Even the XFI used for rather mundane configurations has more lift than the XE-Rs.

The more aggressive ramp allows you to use a shorter seat duration. Yes, if you add a more aggressive ramp to an otherwise adequately cammed combination, you will be adding effective overlap, late IVC, and early EVO without benefit. However, if you took advantage of the more aggressive cam (as Patrick's oft quoted example does) to reduce duration, you gain in all areas with no loss in flow.

The cam is not about total lift. It is about lift everywhere. And there a LSK beats and an XFI which beats an XE-R. And an XE (solid) Street Roller beats all of them by a sigficant amount.

As far as when 'is there too much lift' goes, all the EMC engines were in the .750-.850 range to produce power from 2500-6500. Building an endurance engine, where part life span is an issue including springs and valves, then it might be less. However, I believe .670-.750 would be the range, all greater than an LSK.

I would be very surprised if an LSK with 4° less duration was not more powerful with any of your heads than an XER version, probably with a broader power curve, better drivablity, and not significantly different valvetrain component life.

 

I don't think your reading everything I state. I wrote an article about "area under the curve" that was published in a national magazine 10 YEARS AGO. I understand area under the curve on heads AND CAMS. With heads it is always a good thing, with HYD ROLLER CAMS it is not always so.

Any hyd roller over .600" lift is flirting with disaster, anything approaching .650" is insane. If hyd roller lifters didn't compress, then all of these guys who RACE hyd roller lifters wouldn't be "bottom lashing" the lifters.

EMC engines run solid rollers correct? I have customers with solid rollers of over 1.000" lift, and the cars haul, one runs 157.7 mph ON MOTOR, and it's a small block. As I stated before, this applies to HYD ROLLER engines. I can tell you beyond the shadow of a doubt, as you increase ramp speed and lift in HYD ROLLER applications you don't always get rewarded with more power everywhere, it is often less. I know you are on a quest for knowledge, as I have been for the last 20 years, and I think you are an intelligent guy, but you believe what you believe, and everything to the contray you don't, but hey, I was the same way.

 

There was a thread in another section that went into a long discussion of lifter compression. However, there are people running LSKs with the lightweight LS valves and springs. Whether it is differences in valvetrain mass, spring dynamics, or lifter design, people are successfully running the LSKs. Maybe lower viscocity synthetic oils play a role.

However, isn't the rest an argument for solid rollers in a 500hp 347s?