540 RAT

The new May '09 issue of "Chevy High Performance" magazine has an article on page 24, where they performed a head to head cam LSA (lobe separation angle) comparison on a stout SBC. They used the same motor, same dyno (Westech), 3 identical hydro roller cams, except for their LSA's, 2 intakes, a single plane and a dual plane, and did one test right after the other. This is about as good as you can get for everything being an apples to apples comparison, and makes for some excellent reference data.

The motor details are:
406 SBC
4.155 x 3.750
11.1:1 cr
Dart Pro 1, 227CNC al heads
Dart dual plane and single plane intakes
Holley 950 Ultra HP carb w/ 75/79 jets
1" open carb spacer
MSD 7AL Digital ign
Hedman headers w/ 1 3/4 primaries and 18" extensions
37* total advance
91 octane pump premium fuel

Cams were Comp Cams Hydro Rollers:
248/254 dur @ .050
.600/.619 w/ 1.6 rockers
107, 110, 113 LSA's

Billy Godbold, cam guru at Comp Cams supplied the cams and was involved in the test. A few of his comments:

"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."
"I do know for certain that single plane manifolds have always run best with tighter lobe separation camshafts."


LSA________________107_________________1 10__________________113

IO_______________21*BTDC____________18*B TDC_______________15BTDC
IC_______________47*ABDC____________50AB DC_______________53ABDC
EO______________58*BBDC____________61*BB DC______________64*BBDC
EC______________16*ATDC____________13*AT DC_______________10*ATDC
Vac @ 1000_________6"_________________7"______ ________________8"

Dual Plane Intake
Peak HP________568 @ 6300___________566 @ 6200__________564 @ 6200
Peak torque_____540 @ 4800___________533 @ 4900__________526 @ 5000

Ave HP____________449_________________442___________________4 39
Ave torque_________492_________________485___________________4 80

Single Plane Intake
Peak HP________607 @ 6600___________609 @ 6600**________608 @ 6700***
Peak torque_____543 @ 5200___________540 @ 5100__________531 @ 5100

Ave HP____________456_________________452___________________4 39
Ave torque_________495_________________491___________________4 81

**was 2 HP higher than the 107 for only a 200 rpm range
***was 1 HP higer than the 107 for only a 100 rpm range

A few magazine comments:
"It's not a coincidence that Comp Cams utilizes a 107* LSA in its Thumpr line of cams."
" We've got a very clear demonstration of the advantages-namely a more usable powerband-of running a narrow LSA."

Funny thing, their last comment, which from what the test results showed, is exactly opposite of what most folks insist, which is that a more usable powerband comes from a "wide" LSA cam. Since its hard to argue with a real world test, its better to go with the facts, rather than go just on what people simply say. But to be fair to those people, few, if any, ever have the luxury of doing an honest to God, apples to apples, back to back test of LSA's like the magazines do on occasion. So its easy for those folks to come to the wrong conclusion, due to the fact that almost always, more is changed than just LSA. With mulitple changes being done at once, it is pretty much impossible to say exactly what did what. I've seen a few of these exact types of LSA comparisons in the magazines over the last several years, but they used solid flat tappet or solid roller cams in those. And they had the same results where the narrow LSA cam outperformed the wider ones, except in those tests, the narrow ones also clearly made the highes peak HP as well.

At the end of the day, you'll have to decide for yourself, which cam above you think could move your car down the track or street, quicker.......

2000FRCZ19

good write up. it makes me feel better about my selection of cams and intakes for my 396 sb. i went with a 108 lsa crower and a single plane team-g. i will have dyno numbers in the next few weeks. it has been built for a while but has not been run yet. thanks again for the info.

gerry72

I believe it was Hot Rod (maybe Car Craft) that did the same test a couple years back. Honestly, LSA should be whatever it ends up being just as a consequence of the I/E timing events. Once you figure out the duration and your EC and IC for your goals, then LSA is what it is. Only cases where LSA needs to be a primary consideration is where you are trying to achieve something specific, such as a choppy idle with short duration or a smooth idle with more duration.

TheSkunkWorks

Such magazine exercises often focus solely on HP/TQ numbers with no mention of an engine's manners. IMCO, on the street, squeezing every last pony out of an engine isn't necessarily going to result in the happiest of motoring. As I am perfectly willing to sacrifice a relatively minor amount of peak power to have a tamer beast with a wider torque band, I'm not so readily convinced that the wider LSA with which I am going is somehow a mistake. Besides, I've figured out a long time ago that having a harsh idle is no proof of machismo.

Not opening a debate here, nor arguing with the tests; just trying to give a little perspective on it.


TSW

Gordonm

I would like to see the torque curve of these cams. Peak numbers don't show anything but peak HP/TQ. As said above what is the usable power of the cams. If you are giving up a few ponies up top but having a broader torque curve that would be a better street cam. Any chance you have the torque curves of these cams?

540 RAT

I can tell you that the 107 had the best numbers virtually everywhere. Sorry SkunkWorks, if its not too late, maybe you can switch cams, though of course it depends on what you want. If a real smooth idle with high vacuum is what you want, stay with the wide LSA. But if you want the best powerband and performance, and don't mind a little lower vacuum or a rougher idle, then the narrow LSA would be the way to go. If anyone wants to see the whole set of numbers, you'd need to get that magazine issue, but I do have this stuff from the test:

The averages were determined by using all the numbers from 2,500 rpm to 7,100 rpm for ALL the cams. Yes, that is quite a range.

For the dual plane test:

the 107* cam dropped from 540 ft lbs at 4,800 to 397 ft lbs at 7,100, a 26.5% drop

the 110* cam dropped from 533 ft lbs at 4,900 to 379 ft lbs at 7,100, a 29% drop

the 113* cam dropped from 526 ft lbs at 5,000 to 386 ft lbs at 7,100, a 26.6% drop

So the narrow LSA held on best here.

------

Still for the dual plane test:

the 107* cam dropped from 568 HP at 6,300 to 537 HP at 7,100, a 5.5% drop

the 110* cam dropped from 566 HP at 6,200 to 513 HP at 7,100, a 9.4% drop

the 113* cam dropped from 564 HP at 6,200 to 522 HP at 7,100, a 7.4% drop

So the narrow LSA held on best here as well.
Its interesting that in both cases above, the 110* cam did the poorest job of holding on at the highest rpm.



For the single plane test:

the 107* cam dropped from 543 ft lbs at 5,200 to 437 ft lbs at 7,100, a 19.5% drop

the 110* cam dropped from 540 ft lbs at 5,100 to 425 ft lbs at 7,100, a 21.3% drop

the 113* cam dropped from 531 ft lbs at 5,100 to 428 ft lbs at 7,100, a 19.4% drop

So the narrow LSA held on best here too, in pure numbers, though if you care about %, the 113* did a fuzz better.

------

Still for the single plane test:

the 107* cam dropped from 607 HP at 6,600 to 591 HP at 7,100, a 2.6% drop

the 110* cam dropped from 609 HP at 6,600 to 574 HP at 7,100, a 5.7% drop

the 113* cam dropped from 608 HP at 6,700 to 579 HP at 7,100, a 4.8% drop

So the narrow LSA still held on best here also.
Its interesting that in these last two cases above, the 110* cam still did the poorest job of holding on at the highest rpm.

SteveG75

That article is not online yet but I have the issue in the other room. Basically, the 107 LSA made greater power across the board.

howarsc

This is why I went from a 112 in my 468 to a 108 in the new 498. Will be interesting to see.

63mako

How are they running a Hydraulic roller to 7100 RPM? Those are big duration numbers, lift and monster heads. This is a high RPM build with a hydraulic roller. Seems mismatched. They change the LSA. Are they installing on the same ICL? This will shift the power range and overall power production in itself as your intake valve will be closing at a different point on all three cams. With Gordon. Streetability dont enter the picture at all with an engine bolted to a dyno starting your pull @ 2500 RPM with a nasty idling cam. This build is on the edge of streetability as it is. Which one can you pull away from a stop sign with. What torque convertor would be needed with each on on a street car? I would like to see the torque curves graphed one overlaid on the other from 1000 to max RPM.
Generally a closer LSA produces most peak power in a narrower RPM range and wider will drop your peak but flatten the torque curve. Circle track cams are usually a tight LSA for this reason. They operate in a narrow power band and produce the most power in that band. This test kind of throws the whole of common conclusions proven by many over the years down the crapper.
The 110 is the poorest performer for the most part yet most cam manufacturers use this as their standard performance grind LSA.
Sounds to me like this was sponsored by Comp Cams for the sole reason of trying to market their 107 LSA Thumper line of cams. You have to remember this is a magazine with most of their revenue coming from their big advertisers, comp being one of the biggest. The company that sponsers the test, pays for advertising and ground the cams "honest they are all the same" also happens to have a new line of cam that happens to have the 107 LSA, originally marketed for the ability to have a high performance rumble with a low compression motor. Now they are trying to tell you, not only will it give you that rumble but it is more powerful over a wider RPM range.

OzzyTom

Well you'd always have to be suspicious of any results when the tests are sponsored / paid for by the manufacturer.
And lets face it,
a good contradictory story, sensational headline or other news item which goes against the grain of common knowledge will always result in lots of free publicity and potentially more sales.

advertising 101

63mako

It did get them a bunch of free advertising here didn't it. Probably will get them a bunch of "custom grind" work also. Might even get Skunkworks to sell his custom grind and buy a new custom grind.
Better check it out on your Comp Cams Desktop Dyno software

TheSkunkWorks

No, as a matter of fact, according to the timing events listed the ICL's were not kept constant; all cam variations having apparently been installed with +4* advance, resulting in the following:

107* LSA w/ 103* ICL
110* LSA w/ 106* ICL
113* LSA w/ 109* ICL

Changing ICL moves IVC, which in and of itself would have a significant effect on the torque/power curves. How much can be attributed solely to LSA variance isn't as clear cut as the article would make it appear at first glance. Just goes to show how statistical analysis is often NOT so straightforward.

Good catch.

BTW, haven't ordered that custom solid roller yet, but not changing my crazy specs due to this piece. And, FWIW I only use DD for general overviews, preferring EA Pro for when I want to geek out on data.




edit - This might interest readers... http://www.compcams.com/Technical/FAQ/LSAproperties.asp

63mako

HMMM.................So this is not a true apples to apples comparison. It could be skewwed to favor the tighter LSA........to help sell Thumper cams. No, I don't really think they would do that would they?
That link from COMP CAMS is real interesting especially the part that says a wider LSA results in a wider powerband and the other info we always took as gospel that this article contradicts.
I wonder where they are lying, in the ad-article or on their technical faq sheet.

If you really want to geek out on some data use that EA pro and graph out the HP and torque ratings on their test from 1000 RPM to 7100 RPM. They give you all the info you need. Then you will definitly see the difference at the bottom to midrange where most of our motors live 90% of the time.

I still want to know HTF do they run a Hydraulic roller to 7100 RPM???

TheSkunkWorks

I have to admit I'm a bit disappointed in such an important factor as is ICL apparently being discarded, if not overlooked altogether. But, I must admit that I haven't seen the article in its entirety to see whether or not it's role was mentioned. I should like to think it was brought it up with the writer(s), even if edited out () for seeming to be inconsequential or confusing.



edit - I've run vast numbers of sims with varied LSA's and found that without compensating for later ICL's with more CR it ain't quite apples to apples.

TheSkunkWorks

Curiosity killed the cat, or at least kept him up late...

Did some brief CR comparisons on the 406 in question, and found that the 113* LSA / 109* ICL combo appears to need nearly 0.5:1 more static CR to bring it up to par ("DCR" wise) with the 107* LSA / 103* ICL combo's. Of course, changing CR would have cost someone a good bit more time and $$$. This should prove, once more, that any one change affects everything else. Engine builds are a package deal.

Now I'm going to bed, as the little gray cells need to rest after this one.


TSW

Jason Staley

I take my hydraulic roller to 6500 with no issues at the drag strip. I've been up to 7000 a few times only in 1st gear with no noticable valve float. The only reason I take it up near 7000 rpm is I have a big rpm drop between 1st and 2nd. I'm way past my HP peak in 1st, but this technique helps out 2nd gear ALOT.

Doing this gets me the best 60' times and overall runs ... well at least it did on my older setup, but I haven't been to the 1/4 mile in a year. I'll see if this technique works as well with my aluminum flywheel and new tires.

However, on road courses and the street I shift by 6000 rpm to take it easy on the engine.

Here's my setup:

• 350 w/ L98 Heads
• GM's LT4 camshaft ... to be honest I can't quote all the specs (.545/.545 lift). Got it off a friend of mine for cheap with only 1K miles on it.
• Stock GM hydraulic roller lifters
• 1.6 roller rockers
• Manley "race-flow" valves - 1.94/1.5 stock diameter (p/n's 11521 11522)
• Manley NexTek Springs - 115 lbs installed / 350 lbs open, 409 lbs/in spring rate (p/n 221423-16)
• Titanium retainers
• AFR Hydra-Rev Kit

Nothing real trick and I'm definitely not an engine expert, but the combo ended up being a nice street engine thats fun to run at the track on the occasion.

rham

I think they are trying to be apples to apples because most performance camshafts are ground with 4 degrees advance, this is what was done here but as you mentioned other changes besides lca were made.

David Vizard has been a proponent of tighter lca's for years, he says that there is a correct lca for each engine for max power based on cubic inch to valve size and head flow, big block or small block and compression ratio among other things. I have read several of his articles and books and he seems make good points.

But as has been mentioned camshaft selection is based on compromises. Here are some links to some of Vizard's articles, it is interesting reading.

http://www.popularhotrodding.com/tec...ics/index.html

http://www.hotrod.com/techarticles/e...ech/index.html

DRIVESHAFT

What do you mean?
Based on the numbers posted, overlap with the 107 cam is 37, with the 110 cam its 31, & with the 113 cam its 25.

63mako

With David Vizard that peak power numbers can be obtained with a tighter LSA to a certain point. His charts and graphs are great starting points and references for a pure drag racer. But many other factors come into play. Static compression, Target DCR, valve timing events, intended use, power adders, streetability, vacumn requirements, overlap, idle quality, CI, head flow, cam lift and duration, width of power band, gearing, fuel octane requirements and numerous other factors.
This test is not an apples to apples test. A more accurate test would be adjusting the compression ratio to provide uniform DCR in each cam test as Skunkworks noted. With a wider LSA you will drop DCR so naturally you will lose peak power. Other variables listed then also come into play.
This test is an advertisement for Comp Cams Thumper line of cams, and that is all it is or proves.

DRIVESHAFT

They didnt use any Thumper cams.
Thumper cams all have a huge split between intake and exhaust duration.
The cams tested only favored the exhaust by 6 degrees.

It looks like they used the XR300HR cam with several different LSA.