I have a 2001 2500HD CCSB 6.0 LQ4 towing a 38 ft 5th wheel(12k). it is Magnuson supercharged mp112hh w/4.88 gears. i had a 26 ft trailer 8k and it pulled it great, I would run it in cruise control most of the time. I need more help between under the curve. At 62mph, 4th gear is 2500rpm, 3rd gear is 3200 rpm. What makes a good supercharger tow cam?? There is not alot of info about Supercharged cams for towing applications.. Because if you want that you can just buy a diesel. I am not trying to start a gas/diesel war. At 130k, it may be time to freshen up the motor, so a different cam may help. This is what i am thinking about:

Vinci st2 perf/tow
DUR @ .050" 208*/ 216*
LIFT .530 / .530
LSA 115*
5A

 

What makes a good blower cam? Let’s start from the beginning. As the saying goes, an engine is essentially an air pump. The idea is the more air you can put in, the more power it makes. When in naturally aspirated (NA) form, it relies on the acceleration of air as the piston is on the downstroke, in order to fill a cylinder. On the intake side, we need to consider not only the power range we’re aiming for, but also the head flow. Although the head flow is measured using a constant vacuum, it can still tell us how the heads support cylinder filling. Most stock (read un-ported) LS heads max out (otherwise known as stall) somewhere between .550-.600”. Going above the stall means the additional lift is not doing much to promote flow, so above that the added lift is not producing much benefit. Overlap can help with exhaust scavenging as well as cylinder filling therefore tighter lobe separation are beneficial for power.

Now let’s add a positive displacement blower. The blower has to push that air through into the cylinder. The more restrictive, the more work it has to perform. Imagine blowing bubbles into a glass of water. Pretty easy, right? Now instead of water, it’s a nice thick milkshake. Not so easy now (cheeks puff out, face feels hot). Same thing for the blower. The harder it has to work; the more heat is generated. That heat reduced the density of the compressed air, thus reducing the total volume of air compressed in the cylinder. Less air, less power. Furthermore, to combat the tendency to detonate from the higher temperatures, either less ignition timing or additional fuel has to be tuned in which reduces power. Which is why you may find putting in a cam with longer duration and more lift often produces more power but with less measured boost pressure at the blower.

So back to what makes a good (positive displacement) blower cam. For the intakes side, we still need to consider the powerband target. Since you’re looking very lower in the power range, keep the duration modest. At the same time, because of the blower, we can go above the lift at which the heads stall and still produce more power. In doing so, the engine should respond quickly from throttle tip-in to boost pressure. The exhaust side is a bit of a balance. On one hand, we need a lot of duration with plenty of lift to help evacuate. But at the same time, avoid a lot of overlap because that will bleed down some of the boost. To have a long duration, with little overlap requires a wider lobe separation angle (LSA) than might be chosen for a strong NA cam. And that’s why typically on the OEM cams like the GM LSA and GM LS9 engines, you’ll see big duration split intake/exhaust (18-19 degrees) and wider lobe separations (122.5 degrees). Although they tend to go even more wider than necessary to provide a very smooth idle.

Now let’s look at your setup. Most aftermarket blower cams are designed around performance applications where more peak power is desired rather than heavy trucks pulling 5th-wheels up mountains. So, you’d be best suited to have a custom ground cam. I’d recommend contacting CompCams and seeing if they will grind you a cam with a L3E-13868 intake lobe intake and LXL-13172 exhaust lobe on an intake centerline (ICL) of 110 and a lobe separation of 115. This will result in a 205/224 @.050” lift and .605/.604” max lift camshaft on a 115+5. The low duration on the intake side means we can go a little tighter on the LSA while still keeping the overlap reasonable. And the intake valve closing (IVC) will be really early helping the torque right where you want it. Plus with the .600+” lift it will have the heads flowing at peak efficiency. Then, if you find your setup is producing less boost, you can change the pulley, increasing torque even further.

On top of that, you could add a larger intercooler which would reduce temperatures further, and therefore increase torque as well, while protecting against detonation under high load.

If you do go with the L3E lobes, make sure you use dual springs, hardened pushrods, and upgrade the stock needle bearing rocker arms.

 

Or for something that would work with good beehive springs (like PAC1218s), which would be easier on the valvetrain you could use Cam Motion cores.

They have a 204/.320 intake and 220/.350 exhaust lobe on their list. With 1.7 rockers you could have them make a 204/220 115+5 with .545/.595 lift. And then you can have them grind it on an 8660 core for added durability.

 

would he have to do a converter for either of the ones you specd? or should they play nice?

 

Either would play nice.

 

What tire size are you running?

 

thank you for the ideas. That is alot to chew on.. i would like to be easy on the drivetrain and the most i would want to go is .550 lift. Tire size is 265/75/16 for now. If i didn't tow such a heavy load i would go up to 285/75/16 as I think these trucks came stock with too small of tires to start with.

 

I have an 02 2500hd with a TVS1900, my cam motion cam specs are (218/232 .578/.578 on a 112.5 lsa. I'm running 4.88's also but larger 35" tires. I'm also running a 2800 converter. I think with your smaller tires and stock converter it would work great. What are you running for exhaust?

 

tglandon, This shelf cam should give you more grunt in the low 2000-3500rpm range as you had asked in the other thread: https://sdparts.com/i-24132276-sdpc-...6-0l-6-2l.html It has a tighter LSA than the custom cams I suggested earlier, but considering the low duration, the overlap is still not aggressive, and it has the intake valve closing point is similar. It's on sale at the moment, so pretty good bang for the buck.

 

with it being a .570 max lift, you would need to run bigger then Ls6/3 springs id assume?