Nexus9

I'm going to pose a question that I think is shared by some of us "more seasoned" (read: older ) drivers out here. After owning a few performance cars, I find myself a lot less interested in the "Horsepower" number; which really should be described as "Maximum Horsepower", and exists in a place way up on the rpm scale that most of us (well, me, anyway) spend very little time. In my 2012 LS3, I'm a lot more interested in the torque curve line, and I would be perfectly happy with 400 ft/lbs of torque at 4,600 rpm (as opposed to the rated 420) if I could also keep that 400 ft/lbs all the way down to 2,000 rpm (as opposed to the rated 350, which really feels more like 250). In other words, I'd rather lift the "tail" of the torque curve rather than the "head"; if the head comes up 50 ft/lbs, that's fine - just not the objective. What the horsepower rating is at 5500 rpm doesn't concern me at all. It's a date car, not a drag car.
My experience with building motors in the past indicates that - short of a $7,000 supercharger -the cam(s) can be one of the most influential components in shaping the torque curve; but it seems most people are only interested in hearing about more horsepower, so the manufacturers (rightly so) build what people say they want, and there seems to be very little technically sound advice on creating a flat torque curve from 2,000 - 5,000 rpm. I would be very interested if anyone could share their experience and/or knowledge about reshaping the bottom of an LS3 torque curve without a supercharger, and without a lot of exhaust noise - i.e. specific cams or cam profiles that really worked.

THANKS in advance for your time. Jon

WKMCD

iTrader: (2)

Adding lift and tightening up the stock lsa a bunch is one way. Gears is another.

Just my $.02

HioSSilver

iTrader: (8)

Headers will put alot of low to mid-range in it also.

cam

iTrader: (9)

Have you tuned it yet? The "feels like less" is most likely torque management preventing you from getting the actual power it has onto the ground. But if torque is all you want? Get as much advance ground into the cam as PTV allows and keep the duration below 220 and the thing will tug harder down low than a freightliner

raymond mckinney

iTrader: (4)

Small cam,headers and a tune will get you a huge improvement in tq and feel. And if its not enough a set of gears will do the trick.

Tainted

iTrader: (9)

Good heads with lots of velocity, tight quench, cam matched to your specs (pat g is one of the best), and the right gears

Hard Core Z28

Tri Y Headers is what you are looking for.

litle88

iTrader: (20)

How about a 454 from a 1992 454 SS comes to mind
Just my .02

COPO9560

More cubic inches is a great way to increase low end torque. A 4 inch stoke with your existing LS3 heads and a custom cam would provide a significant gain.

topbrent

iTrader: (1)

Yup, headers, higher lift, faster lobes, tighter lobe separation angle, earlier intake valve closing point, are some of the basics.

ramairroughneck

iTrader: (35)

Gears, gears, gears. Instant throttle response you can feel. The others you'll have to look on a dyno sheet to be able to tell if gained anything.

Nexus9

Ha ha... NOW we're talkin...!

Nexus9

Okay, thanks for all the input. I don't want to go too wild on this thing (boring, stoking etc) - remember, for $8,000 I can install an Edelbrock supercharger and solve the whole problem with an easy install - so I need to be able to justify the internal motor work with at least $3,000 left in my pocket. What I'm coming up with here is a set of LG Motorsports Long Tube Street headers with X-pipes, a K&N FIPK, a cam and a tune. The cam data I can accumulate is different from what I'm used to using (Harley world) - so I have a few questions regarding that:

1. What would be considered the highest lift reasonable for stock valve springs?

2. How does one calculate neccesary pushrod length?

3. Does separation angle affect IVC? Very little IVC information from the cam manufacturers out there, can I calculate it from Duration / Separation angle / Centerline?

4. How do I adjust total advance/retard of the cam - I don't see any adjustable sprockets. Custom grinding?

5. The 111 - 112 LSA cams I have heard on YouTube have noticeably rough idles - at about what point does the idle start to smooth out? 114 fairly smooth?

Thanks again for your valuable time. Jon

Tainted

iTrader: (9)

1: stock springs will not do
2: pushrod length checker
3: got me here
4: most people go dot to dot method
5: the higher the lsa the smoother, but a lot has to do with tune as well

Nexus9

Okay, after a little cam spec study, I've got the answer to 3. - the all important IVC. (still can't figure out why that's such an obscure figure in the car world) Using Duration and Centerline, we would divide Intake duration in half and distribute that before and (most important) after centerline to get IVC. For example:

Comp Cams 269LR HR12

Duration at .050" = 219*

Lobe Centerline = 107* ATDC.

219/2 = 109.5*

Distributing 109.5* before and after 107* ATDC, the intake valve will be open .050" at 2.5* BTDC and would be .050" from closing at 36.5* ABDC. Stock IVC at .050 is 43* ABDC, so this CC 269LR would boost Dynamic Compression Ratio and cold cranking pressure about 5 psi.

That's helpful in determining how a motor will behave with a particular cam in it. Separation angle must be determining overlap. I need to spin the cam around in my brain a few cycles to get a handle on that, and right now, it just TOO DARN LATE...!

NemeSS

iTrader: (127)

I've always had success, and recommend the LPE GT11 cam for that strong, instant tq, sot, throttle response. I've had this cam in heavy auto cars, and recommended based on my experience with it. Don't let it's low duration fool you, it's aggressive but IMO will deliver what u are looking for. It also a profile suited for rectangle port heads, although originally designed for cathedral port heads. It is extremely responsive in 6.0 motors with common scr.

topbrent

iTrader: (1)

Here is a handy calculator for figuring open/close points.

Camshaft Intake Open/Close Calculator: http://www.wallaceracing.com/cam-deg-calc.php

Comp 269LR HR12 Cam specs: http://www.compcams.com/Company/CC/c...ookieSupport=1
- .607/.614 - 219/227 - 112/107

IVO 2.5° BTDC
IVC 36.5° ABDC
EVO 50.5° ATDC
EVC -3.5° BBDC
Overlap -1 °

Looks like it would be a snappy and responsive cam.

Nexus9

Brent,

Thanks, that's exactly what I was looking for.

Jon

Nexus9

NemeSS;

That looks like a good cam - a lot of lift, short duration. And no, I'm not fooled by short duration, and I'm not another one of these guys who think that small numbers = bad, large numbers = good. My experience with cam installations is that shorter duration, higher lift cams with earlier intake closing (to a point) "feel" a lot more powerful in normal day to day driving - although they also sign off earlier in the rpm band. Which I'm good with - I don't want to have to downshift two gears every time I pass a car.
I talked to Ryan at Lingenfelter, and answered two more questions: The LSA on this cam is 118. When I listened to a YouTube video of this cam installed in an LS3, it sounded good - low and throaty but not choppy (which is what I want) A lot of guys are really pushing the limits with these 111 - 112 LSA cams, but I'd rather stay a little closer to the stock LSA. Using the Wallace Racing calculator, we get an IVC of 45.5 - which won't improve CCP that much.
The next important question answered is the limits of the stock springs, which Ryan said was about .580 - not much higher than the stock cam lift of .551.
More pieces fall in to place. Thanks for the help and good info.