I've seen cams with LSA's from 111 to 118. Just curious how a cam with say 230 and .600 lift would behave with 111 LSA vs the same cam with 118 LSA. I've done lots of reading, but I guess that most of the LS3 cams are still "secret". When someone asks about a cam rec for an LS3, the reply comes back, "our BR549 is exactly what you want". No mention of specs. Looking to learn. Help appreciated.

 

The lower the LSA the more power it will potentially make, but, the lower the LSA the worse drivability gets. So, to make more power you give up drivability, depending on how aggresive you go depends on how much drivability you lose.

 

Cams get designed with the LSA it needs and its not a like/dislike variable. As duration climbs, you choose the valve events that make the cam peak at a certain rpm. The FAST manifold for example forces a peak at 6300 on a 6 liter due to its set runner size. A cam that does the same will need an intake valve closing point of about 47 degrees. As you increase duration, the power band climbs and LSA widens making the power band move up and narrower brings it down. You can also change such events by advancing or retarding the cam timing with the same LSA and the power band moves up with retarding and down with advancing. Getting the intake valve to close sooner helps low end TQ because it builds cylinder pressure sooner. This is why you can run more compression with big cams because the dynamic compression is lower with a given static compression. A higher DCR also pays dividends at the power peak too. In fact high rpm power while enhanced with the narrower LSA is doing so because you closed the intake valve sooner but this can be done by advancing the cam and staying on the same LSA. Staying wider on the LSA and bumping compression is going to give great power throught the rpm band and results in less driveability issues. More compression makes a cam act like its in a bigger motor.

You dont pick an LSA because you like it. Its chosen to make a usable powerband. There is some variance with this. Cams with 44-48 intake valve closing points work with varying results but generally are fine.

A 244/248 cam on a 118 may sound like a nice streetable cam by the wide LSA theorists but it isnt about just LSA for driveability. In a 6 liter it will peak over 7200rpm. Driveability is a function of overlap and LSA afects it but so does every other spec (except advancing it). Intake duration and exhaust duration both contribute as does LSA. So while a 232/240 on a 114 will lope lots (overlap is +8) a 224/228 on a 112 will lope less (overlap is +2). No hard and fast rules here.

The stock cam in on a 118 or something high like that and its 204 intake duration makes for a HP peak at 5800. A 236 on a 118 wouldnt be usable.

I myself am in the earlyt stages of learning this stuff so maybe someone like Glass Slipper will chime in and learn me some.....I'm practicing my cowboy-mountain speak.

What I'd like to hear about is an explanation of reversion and why high rpm power is affected by it. This is a narrower LSA question I guess.

 

I have looked around on the net seeing if I could find dyno graph overlays comparing 2 cams with the same durations/lifts with different LSA...so far...natta...I am trying to compare power ranges of several cams but with an A6 off idle drveability issues being more concerning as my car is my DD, I just have not been able to develop any mental comfort that the 224 228 114 that I had in my manual C5 with pro tune will drive well at 1000 rpm in 35-40 mph traffic in my A6. I have looked closely at the LPE GT11...scary lift and the midrange will likey be no different than stock ( not a bad thing really). If anyone can find any comparison graphs concerning the similar cams with different LSA's ...please post

 

I just wish that someone who is dynoing these great cams would just show the grinds so we can learn. Everybody seems to have thier own grind and recipe but I bet since everybody (it seems) is getting great results from the LS3 cams, they ALL must be in the same ballpark on grinds. Hell, they may even help get MORE power out if they would help disclose thier findings.

If i kept the LS2 heads, I could pick my own cam with no problems but with the LS3/L92 swap, I dont like having to "trust" another person to pick my cam. Why so secretive?

 

If you call me, I will help you pick the cam YOU want.

LSA helps with a lot of things, but it can hurt others. Its all a big trade off and what you want the combo to do.

LSA is only one part of the equation, but the tighter the LSA ( 111 is tighter than 118) it will lope more and make more midrange power. Wider will lope less and make more top end power.

Its finding that fine line between too tight and too wide to fit the combo

 

Here's one example http://www.popularhotrodding.com/tec...ics/index.html

It's by David Vizard, pretty smart cookie.

Here's one from Marlon Davis

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

Bear in mind that both articles are written with carbed motors in mind, but the premise is the same. But do be aware that there are differences between a carbed motor cam and an EFI motor cam.

Vizard has some excellent books out on cylinder heads and cams.

Another excellent tool, and one that Spin has mentioned he uses is engine modeling. There is DeskTop Dyno by proracingsim originally Motion,which was bought by Comp Cams, . And there is Engine Analyzer from Performance Trends that comes in various levels depending on your pocketbook and needs.

 

I suspect that since you said 'stay with the LS2 heads', you mean that you do not have a 6.2 liter. The LS3 reacts differently and the bigger displacement is making more power everywhere in the power band over the LS2. L92 heads on the LS2 is not the same for cam picks. The LS3 has .3 more compression with the same p/v clearance for all chamber sizes/gasket thicknesses. The bigger bore makes more power all around not just because its bigger but because it unshrouds the valves. I think in the end its a 10-15 hp difference, the TQ may be a different story.

The LS2 heads dont compare but if you want a huge cam then aftermarket heads are a btter choice. Since driveabiltiy comes into this equation, the size issue seems to be a moot point. Since there are established cams that make great power and fit the L92's why reinvent the wheel. I tried 4 cams with the L92's and posts all the specs.
224/230 XER 114+2: 455rwhp
228/232 XER 114+2: 472rwhp (462 through 4.10's)
228/232 XER 114+0: 471 through 4.10's, alum fly, and lightweight wheels (480rwhp?)
MTI G1 cam: not dyno'ed but felt like 450-460rwhp.

None of these builds used ported heads.

Zero driveability issues with a 228 cam and 470rwhp doesnt sound so bad. A 224 XER cam will be fine in a A4 or A6 at all rpm's as far as manners with the lower rpm idle. I'm not selling anything so you can take what I did for free. Some other members posted using the GT 11 cam 215/230 from LG and made 450-460rwhp. They are all great picks. Even Texas speed used a single pattern 228/228 for 460rwhp. The best advice I can give is to not go too big if you want any low end. If you go bigger, use LG's cam. It sees 475+ every time and there isnt any brain work since Louis aready did it all.

 

Exactly what I was looking for, thanks. Patrick G speced me out a cam that I can use with the A6 and with 150-200 shot and it was nearly identical to the one I highlighted. He has 609/604 lift though. The main reason for this is for me and others to learn.

LG has been great about wanting to help and even helped me with a few pm's on LS1tech but the secrecy is odd. Thanks for your info though. Well see how CNC'd LS3 heads/Weiand LS3/Pat G or LG cam will do on an LS2 shortblock. I dont think the .2 difference in displacement will be much at all really but as soon as it goes from too much nitrous it will be much larger than that anyway.

 

Secrecy is something we carry with a LOT of things. we have kept cam specs secret since day one back in the late 90s and carried over to every platform we offer.

Our LS1 cams, the G5 series have been so successful that they have been bought, cam doctored and you can usually find the specs on any of those quite easily. I will tell you most of those specs today, but the LS3 and LS7 stuff I keep to my heart. At least buy the cam if you are going to copy it We worked hard, spent a lot of money on the dyno and time with techs changing cams and setups to just give the specs away. I know I spent WAY too many LATE nights tearing my own car apart and tuning the snot out of it.

Regardless, the cams Spin listed are very middle of the road. Great midrange, great driveabity, great power. Cant go wrong with any of them

 

Right or wrong, on my '08 6speed man, I'm going with the CompCams XER281. 232/234, .595/.598, 112LSA. Other mods include tune, 4.10 gears, EXcellerator intake, UD crank pulley, LG long tubes going into stock mufflers (no cats). I'll let you guys know how it turns out. Hoping it will run hard, yet be semi civilized when asked.

 

Love to see how that idles when you're done. Gonna do anything to the heads or run a thinner gasket?

 

Have no plans to do anything to the heads. I've kind of drawn a line about right where I am....that I don't want to cross. I'm guessing it's going to sound a little mean at idle. I've heard quite a few exhausts, but never heard an agressive cam with stock mufflers. Don't know what to expect there.

 

Underdrive pulley, right?

 

Yessir. Underdrive pulley.

 

I have the GT11 cam and it's designed by Lingenfelter not LG. Probably the first mistake made on the forum by Spin ever. It has .631 intake and .644 exhaust lift and 118 LSA. It very different than almost all the other performance cams. Because of the lift, it required new springs to avoid coil bind, they use the Patriot's which are designed for up to .650 I believe. You also can't advance/retard without getting into trouble with valve/piston clearance or fly cutting the pistons.

I picked the GT11 because I also got ported heads and wanted a cam that idled like stock. Having more power with a longer duration cam simply was not worth it to me if the idle was choppy or hurt the street manners. I can say positively no one will know you have a cam if you listen to the idle. Very smooth idle at 725 rpm. Go to You Tube and do a search on "GT11" if you want to listen. The only thing I have noticed is a slightly rough idle for about 5-10 seconds after a cold start before it smooths out. You can easily have this cam for your daily driver.

But with the GT11 higher lift, better flowing heads are a good idea. In other words, it makes no sense using a high lift cam with heads that don't have increased flow over .600 lift. As my signature states, the report from the dyno was 440rwhp/404rwtq. It has the same idle and drive ability as stock but has pretty good power. The combination of Stage 2 ported heads, headers, and Corsa Sport exhaust also round out this combination.