TheSkunkWorks

Absolute peak power isn't everything to everyone. It depends of what one's purposes are as to whether closer or wider LSA's are the correct call. Admittedly, for some specialized applications, the higher peaks of closer LSA's at the expense of a narrower power band does work. However, for a good many others (and in particular on the street) a broader power band is more desirable than is a peaky power curve.

THE KEY POINT NOT TO BE OVERLOOKED: Properly match a given combo up with the same cam with narrower or wider LSA's, and the average torque and horsepower under the curve over that engine's entire operating range will essentially be a wash. To ignore this context, is to focus so much on the trees that one can't see the forest. Fortunately, those of us who've been down the trail a few times can pretty well manage finding our way thru the woods, thank you.

I am quite unanimous in my opinion that a "wide" LSA (relative to the article in question) is the correct call for the solid roller 427 BB build up in the works for my shark.


...guess my 6.385" rods are all wrong, too.



63mako, I'm with you.

540 RAT

This response is to address the questions/concerns/complaints that some folks had about the fact that this Magazine cam comparison didn't use the same intake closing point for all the cams. Of course everyone is entitled to their own opinion, and that's fine. But, I believe those issues are unfounded, and here's why. There is absolutely nothing engraved in stone that says any assortment of cams needs to have the same IC point, not even similar ones being compared. Comp Cams' top guru Billy Godbold provided the cams for this test. And the guy is no idiot, he is one of the top cam guys in the nation. And he knows more than most of the rest of us will ever know about cams. He knew full well what he was doing with this cam comparison, and set them up the way their ICL's could have been called for on each one's own cam card. The same as if 3 separate guys had each bought one and installed it individually. So, the test represents what buyers could reasonably expect a valid comparison to show. There was no big conspiracy involved to try to make the narrow LSA shine in an attempt to make the Comps' Thumpr line of cams look good, but rather the Thumpr cams are setup that way because it works. And this test shows why it works. There have been several of this type of test done over the last several years, by various magazines, and they all had the same results, where the narrow LSA ruled the day. Don't forget that Joe Sherman said it has always been this way, and probably always will. And he's seen more than most of us ever will. There is absolutely nothing new here, its really more for young guys who haven't seen it before.

Now, let's say that the 110* cam was the baseline cam, and then the other cams, each went 3* the opposite directions in terms of LSA. So, let's compare 2 cams at a time to keep things a little easier for some to follow:

LSA………………………….110*…………………107*……………..diff erence on the 107*
.050 events
IO……………………..18* BTDC………………..21* BTDC……………….3* earlier
IC……………………..50* ABDC…………….....47* ABDC……….………3* earlier
EO…………..………..61* BBDC……………….58* BBDC……………….3* later
EC……………………13* ATDC……………….16* ATDC………………..3* later
OVERLAP…………..….31*…………………….….37*…………………… .6* more

So, you can see here that the 107* cam's timing is evenly balanced on each side of the 110* cam's timing, for a nice incremental difference for comparing one against the other. It looks good to me, and it's what I'd want to see myself. So, I agree with Billy and the Magazine here.


Note for new guys: the 107* cam shows 6* more overlap, while only having 3* difference in LSA. This is because LSA is given in CAMSHAFT degrees, where everything else is given in CRANKSHAFT degrees, which of course is double the cam degrees (remember the cam and crank gear sizes).


Now, let's see how things would compare if we had used the same IC point for both cams, by retarding the 107* cam by 3* to match the 110* cam's baseline:

LSA………………………….110*…………………107*……………..diff erence on the 107*
.050 events
IO……………………..18* BTDC………………..18* BTDC……………….same
IC……………………..50* ABDC…………….....50* ABDC……….………same
EO…………..………..61* BBDC……………….55* BBDC……………….6* later
EC……………………13* ATDC……………….19* ATDC………………..6* later
OVERLAP…………..….31*…………………….….37*…………………… .6* more or still the same, of course

So, now with the matching IC point, instead of being evenly balanced on each side of the 110* cam's timing, its skewed to one side. You could certainly test it this way to see what you get, but its not exactly making a uniform incremental change for comparison, is it?


Now let's look at the 110* cam as it compares to the 113* cam:

LSA………………………….110*…………………113*……………..diff erence on the 113*
.050 events
IO……………………..18* BTDC………………..15* BTDC……………….3* later
IC……………………..50* ABDC…………….....53* ABDC……….………3* later
EO…………..………..61* BBDC……………….64* BBDC……………….3* earlier
EC……………………13* ATDC……………….10* ATDC………………..3* earlier
OVERLAP…………..….31*…………………….….25*…………………… .6* less

So again, you can see here that the 113* cam's timing is evenly balanced on each side of the 110* cam's timing, for a nice incremental difference for comparing one against the other. Same idea as the 107 compared to the 110, only here it went the other way. And again, this looks good to me.


Now, let's see how things would compare if we had used the same IC point for both cams, by advancing the 113* cam by 3* to match the 110* cam's baseline:

LSA………………………….110*…………………113*……………..diff erence on the 113*
.050 events
IO……………………..18* BTDC………………..18* BTDC……………….same
IC……………………..50* ABDC…………….....50* ABDC……….………same
EO…………..………..61* BBDC……………….67* BBDC……………….6* earlier
EC……………………13* ATDC…………………7* ATDC………………..6* earlier
OVERLAP…………..….31*…………………….….25*…………………… .6* less or still the same, of course


Again with the matching IC point, instead of being evenly balanced on each side of the 110* cam's timing, the 113* cam is now skewed to one side as well, but of course the other direction. And now its again not making a uniform incremental change for comparison.



If you had enough time and money, you could make a nearly unlimited number of comparisons, depending on what all you change. Dyno owner/operators out there can of course, feel free to do their own test the way they want to do it, then post the results. But the Magazine obviously did a lot of thrashing as it was, to compare 3 cams and 2 intakes. And they have schedules to meet just like everyone else, and of course time is money on the dyno. All in all, I think they did just fine, and I think the test provided a lot of good information. And it says something, that Joe Sherman himself expressed no complaint with the way the test was done, and he is not bashful about hammering something he does not like. As a matter of fact, he did one of the previous cam comparisons in one of the magazine articles that I've seen in the past. If this test was good enough for Joe, I guess its good enough for me as well.

63mako

LS7 Camshaft for late model GEN 3 & 4 small block engines. Original equipment for 2006-08 Z06 Corvette's with 427ci LS7 engine.
Cam Specs:

LSA 120
Int Exh
Lift 0.593" 0.590" (with 1.8 rocker ratio - stock LS7 ratio)
Dur @ 0.050" 211 230
Centerline 116 124

540 RAT

Since this is a discussion about SBC's and their LSA's, let's take a look at methods used to select that cam in the first place, as it relates to LSA. Most cam designers and engine builders will tell racers and gear heads to start with some particular LSA number and THEN decide on the lift and duration. And of course you hear guys say this almost everyday, that they are going to be picking a new cam, and that they will be using "such and such LSA", but that they haven't yet decided on the lift and duration. Its been done that way for decades, and those folks see no reason to do it any differently, because they've always done it that way, and they feel it works just fine. Typically the idea of overlap is not even considered. But of course, if you just do something the way you've always done it, you don't have the opportunity to improve what you do, or to move forward. If we always just did what we've always done, we'd still be riding horses instead of driving Hotrods and Race cars.

I've always felt that the idea of just starting with some given LSA as a starting point, simply made no sense. And that LSA has no value at all, in and of itself, because of the fact that its "overlap" that defines an engines operational characteristics. And that LSA is merely a by-product of that overlap. Of course, I've always gotten a lot of flack for saying that, from all those folks who "know better". But do they really? I do have a strong high profile figure on the same side as me though. Comp Cams guru Billy Godbold and I share the same philosophy, but of course he is the one with National Celebrity status and all the credibility. And he said this:

"LSA doesn't mean anything except for how it affects the camshaft centerlines. You determine the centerlines, which determines OVERLAP, and THAT has performance effects."

Hmmmm, could it be that I'm not that far off after all? Let's take a look to see if I can make a case for what Billy and I believe. So, let's say some old time cam designer or engine builder tells a young kid that he should use a 110* LSA for an old flat tappet SBC that he want's to do his first modification on. So, the kid pulls out a Comp Cams catalog and looks up solid flat tappet cams for it. And since he was told to go with a 110* LSA as a starting point, he comes across these two cams:

CAM#………….ADV DUR…………….050 DUR
#1……………….270/270……………….224/224
#2……………….290/298……………….252/260

Now, anyone at all familiar with cams would see quite a difference between these two, wouldn't you say? Old Pro's know what they are seeing, but the kid can't tell much between them. And yet they both have the SAME recommended 110* LSA. So, targeting that particular LSA didn't tell the kid anything at all in terms of how the cams will operate/perform in his engine. But if he'd calculated "overlap", using the procedure below, he'd get an adv overlap of:

#1 = 50*
#2 = 74*

A huge difference to be sure, but again, they have the SAME LSA. Now if he looks at the adv overlap reference chart below, he'd see that cam #1 falls into the lower-middle range of the street performance category, a mild grocery getter cam by any measure. But that cam #2 falls into the upper range of the street/strip or the bottom range of the race categories, a wicked race cam by almost any measure. Oh yeah, did I mention that even though they are radically different cams, they still have the SAME LSA? Imagine that, it the "overlap" to finally show him that he is dealing with two entirely different cams that have COMPLETELY DIFFERENT operational characteristics. So, now he can make a much more informed buying decision.

This is just a single example of how LSA, all by itself, does NOT make a distinction between operational characteristics, and is virtually useless in defining a cam. But on the other hand, OVERLAP absolutely DOES define a cam's operational characteristics, every time. So, it makes much more sense to go in knowing how much overlap you want, then select a cam based on that, which will best meet your needs. It all seems pretty basic and straight forward to Billy and me. In fact Billy has previously said the following for choosing a cam:

"Decide on duration and overlap, then LSA fall where it may"
"Choose duration based on target operating rpm"
"Choose lift based on head flow"

That all makes perfect sense to me as well, but those "know better" folks can feel free to clearly show how using LSA as a primary consideration, can in any way, be superior to looking at OVERLAP, in terms of defining a cam. Since cams can be wildly different with the SAME LSA, while OVERLAP always tells the tale.

-----------------------------------

APPROXIMATE naturally aspirated, "Small Block" adv overlap "operational" reference chart (really only suited for solid cams because of using adv numbers):

9* - 35*….towing
26* - 53*….ordinary street
44* - 66*….street performance
61* - 79*….street/strip
74* - 87*….race
83* - 100*...Pro race

------------------------------------

Here's the CORRECT way to calculate your cam's ADVERTISED OVERLAP which is needed for the chart above:

Add your intake and exhaust advertised duration (duration at .050 will NOT give you the correct overlap)

Divide that answer by 4

Subtract the lobe separation angle (LSA) from that answer

Multiply that answer by 2, and you have the CORRECT adv overlap to use in the chart above

2000FRCZ19

i picked my cam by the lift and duration and by seeing what that cam had done on similar builds. then it was run through several sims to see what the change in lsa would have on the power and where the power seemed to come in. since i am going hyd. roller i wanted my peak to be a few hundred before 6500 rpms. the 108 gave me this earlier peak and it gave a better over all power curve in the rpm range i was looking for than say the 110 or 112. i advanced the cam 4* to bring the tq in sooner also. i can always retard it for more power later if need be. this cut some of the peak power that the 108 brings but it also lets the power be right in the target range i wanted. the overlap came out to 73 and that is right in line with my intended use. street strip. i was willing to give up a little on the idle quality to get everything else i wanted. cams are give and take in any combo.

63mako

Where does this 7000 RPM redline motor which by the way, is an 11 to 1 Compression 427 CI with the highest HP and torque ratings ever achieved in a factory N/A small block come out on your chart?
Figuring a conservative ramp rate it is under 35. The new ZR1 has less overlap. That puts them both in the towing catagory. I would say overlap does not always tell the tale.

Oh, My number is 65. Same exact cam on a 107 is 79......And wouldn't run on pump gas. This shows the difference in streetability achieved by bumping LSA. It will also not make quite as much power.

2000FRCZ19

just to stir the pot a little. the 120lsa of the ls7 is used so that thing will idle smooth and produce a cleaner exhaust gas. there are guys going with aftermarket cams in there with much tighter lsa's and getting even more power. they still run on pump gas and are producing more power. they just loose idle quality and the extra overlap causes the "bad for the earth" exhaust gases to be higher. factory stuff is influenced by more than just power. i dumped my stock 117 lsa cam and gained 50 rwhp from a 224/230 @.050 on a 112 lsa. down side lumpy idle. ( i like it but some dont ) upside more power where i want it. it pulls harder to redline and has lots more tq all over the power band. in my opinion the lsa can be manipulated to fine tune an off the shelf cam's power curve or to get more peak power. it also depends on if the car is going to run no2 or forced induction. there is no one lsa that is best fo all combos. each has its place for the intended use and combo.

5abivt

cool thx for posting. Makes me angry that my old builder built my ltx with a solid roller and used a...sigh... 115.5 lsa.. he kept claiming nascar uses 118 and so on and so forth. AT least my new builder has brains.

63mako

100%. The LS7 has great heads, intake and exhaust. It also gets 28 MPG. and has to meet emissions. But it is built to pull great power numbers and be very streetable with 11 to 1 compression in a good part because of the 120 LSA and reduced overlap. It also pulls 90% of peak torque from 3000 RPM to the 7000 RPM redline. I have nitrous, great heads, intake and exhaust. As 540 Rat said, I picked my duration to match the RPM range I want power in, picked my lift to compliment my heads, picked my LSA because I want a decent idle, vacuum, mpg, ability to run 93 octane, performance with 10.4 compression and also to give my nitrous what it wants. Simulations show a 175 HP increase with a 150 shot with this duration. Your LSA is probably a good choice for you, meets your goals. Mine is probably a good choice for me, meets my goals. The LS7 cam is probably a good choice for it, meets their goals. It all depends on your goals and intended use. BTW your 224/230 cam with 112 LSA had a lumpy idle. My 236/242 HR cam on a 114 LSA will have a much lumpier idle than that one due to more overlap. To state, flat out a 107 LSA is the best option for the motor in the article is rediculous. Depends on your build specs and goals.

2000FRCZ19

i also was not worried about vac. with my 108 due to the fixed headlights and the hydroboost. we have close to the same cam. mine is 236/240 with a little more lift but i am running more cubes at 396, so that will give me a little edge on the low end tq so the 108 is even less noticable down low. our heads are the same. my comp is at 10.5 but i will have more overlap so that keeps our dcr close to the same. it came out to 8.24 if i remember correctly. i am looking forward to getting this thing on the dyno so we can see where the numbers end up in the real world. this is not a d/d either so the nasty idle will not bother me. i was going for the old school lumpy idle and the lsa gave me that and kept the power where i wanted it. lsa is just a tool just like duration and lift. it all has to work with a complete combo to get desired results.

540 RAT

Well for one thing, you are only guessing on the adv duration numbers for that cam, so you could be off by quite a bit. Plus by saying it is a towing cam, just to make your point, ignores the fact that the chart shows it at the very TOP of the towing category. But it clearly is a much better fit into the middle of the ordinary street category. So, if you don't try to sway things one way just to make your point, things look a bit more realistic. Say what you want, but a 211*/230* duration at .050 cam IS a grocery getter cam, by any measure. Dude, look at the lift on that cam. Don't see too many stock motors with that much lift do you? Being a smog motor, they traded duration and overlap, for huge lift, which its heads could support. So, between the unusually high valve lift, good flowing heads, high compression, big block sized cubes, fuel injection and computer controls, GM made a real nice, fast stock motor that meets smog. I say good for them, they did a real good job. But the cam itself, still fits the overlap reference chart just fine, so it DOES still tell the tale. Put a cam with those duration and overlap specs into a traditional stock carbureted 350 and see what you get - granny's grocery getter. And it will NOT run like a Z06 motor. It takes the "whole combo" to make the power that the LS7 makes.

And as for the ZR1, now you are really reaching. Get a clue, that is a blower motor. Apples and oranges............

63mako

I got a clue. Got it from reading your posts. Care to guess what it is?

"It takes the "whole combo" to make the power that the LS7 makes".

120 LSA, low overlap cam and all. Been saying this all along.

Little Mouse

LS7 has really big runner heads good sized valves you don't need high duration cams with good airflow big runner heads, you can cut way back on a cam for good street manners if you already have the breathing in the heads, it has $1600.00 worth of light weight titanium valve's to even get it to 7000 rpm. The C5/C6 quality of the car itself is worlds better, to me the new LS7 engine does not make much power for what it is, friend of mine owns a C5 Z06 test drove the C/6 LS7 he was not impressed with its power.

63mako

Head flow makes a huge difference in the duration you need to make good power. You can also use a wider LSA with great heads. But to cut that duration on an 11 to 1 engine you have to widen the LSA to reduce cylinder pressures to be able to still use pump gas. Your friends C5 ZO6 has 100 less net hp than the LS7. 500 RPM lower redline. Really don't know why he wouldn't be impressed. The LS7 cam is the 2006-2008 ZO6 505 HP. That is not flywheel HP but Net HP. Would put Flywheel HP close to 600. This is supercar territory. With a 211/230 duration and a 120 LSA cam.I think those are pretty respectable numbers for an engine that is a 2 valve per cylinder, pushrod type valvetrain, meets emissions, has excellent street manners, pulls 90% of it's maximum torque from 3000 to 7000 RPM, and gets 28 highway MPG. Kind of like having your cake and eating it too.

Cam selection is always a trade off. You want peak power and big overlap you will give up some low RPM power, bottom end throttle response, fuel mileage. You want good street manners you will give up some power up top. These are undisputable facts.
As I said before it all depends on your goals. A blanket statement that a HP small block needs a 107 LSA cam to make big power totally disregards some goals such as streetability. Also the op's statement that the 107 LSA cam would provide the best overall driveability in the 11 to 1, 600 HP 406 is wrong in so many ways I am tired of pointing them all out.

Little Mouse

The late model model engines have extremely good combustion chamber
shapes better piston top shapes they can tollerate high compression ratio's even with 91 octain, the computer even if you go to low on octain level quickly detects a problem basicly retards instantly. My friend on his C5 will get tight on money put in lower octain fuel then its ment to run on he can tell a difference in the power level after the computer compenstaes for his tightness lol.

Really trying to make any comparisons to the Gen 1 and the later model
engines is like trying to make comparisons between Phyllis Diller and
Raque Welch back when they were both younger.

63mako

It is an apples and oranges comparison. But so is the street manners in the test engine between a 107 and 113 LSA cam. The modern Gen 1 aftermarket heads and pistons are also a much better design and the new heads flow a lot more than stock. Fuel injection and computer controlled timing is a big plus for detonation resistance.

What do you really think? In the case of the 11 to 1, 600 HP, 406 would you give up 17 HP for better idle quality, better bottom end, more vacuum, improved off idle throttle response and a substantial improvement in MPG in a street engine? I did! Some wouldn't! And Phyllis Diller has always been scary.

cardo0

Katech builds engines for the Corvette Lemans racing program.

Katech Torquer LS7 Camshaft: SKU: KAT-4727

Specifications
Specifications: 220 / 224 @ .050, .615 / .648 lift, 110 LSA +004

Yes, 110 LSA +004

cardo0

63mako

Yep, Full blown race engine. What else is modified? More compression? Are they running the same fuel you buy at the corner station? Bet the street manners suck. You are obviously not grasping what I am saying. I will try again. A 600 HP small block with 11 to 1 compression is very difficult to build in a streetable combination. With a 107 LSA cam it is not very street friendly. Same build with a 113 LSA cam is much more streetable. I have said in every post you will give up a little top end power but in this build it would be well worth it to me to be able to take off from a stop sign without having to launch the car. As basic as I can say it. If you still don't get it you are incapable of absorbing information.

DC3

Ok, so I read the entire thread and now my head hurts. But I do have a question. I've been told that, to an extent, a larger LSA is better for fuel injection. If true, why? Is there an optimum LSA for fuel injection or does it depend on the rest of the cam specs and/or the entire engine package?

DC

63mako

Good point. Yes, look at the aftermarket cams. The FI cams are a wider LSA. FI runs leaner A/F ratio's. Wider LSA helps avoid detonation that can be brought on by running these leaner mixtures. Anti knock sensors will dial the timing back if detonation is detected but that also sacrifices power. You can run more compression with a wider LSA cam without detonation if they are installed as they were in the test engine. It always depends on the entire build and the intended use!