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I have an LQ4 with an M122 blower from the Caddy STS-V. Prior to the blower, I installed a Low Buck Truck (Truck Norris) cam which worked great. The only issue is that the lopey idle is causing rotor slap/rattle. I'm just beginning to rebuild a short block to replace the 200k one in my truck and will take the opportunity to add some ring gap and also change the cam to something with less overlap. Planning to stick with 317 heads and my .560 beehives. Stock converter on the 4L80E for now, but will probably move to a ~2800 stall at some point...possibly during the engine swap.
Most of the PD-specific cams have a lot of exhaust duration, which I understand to be good for fully evacuating the cylinder. They also seem to have a lot of LSA, which would be good for idle, but tends to shift the powerband upward, which I don't need. The truck doesn't "blow the tires off" my 34s at any RPM now (8 psi), so I don't feel like losing any low end in the name of traction is a great thing, though I do feel like the power tapers off at higher RPM with the blower, which it did not when NA.
I understand camshaft basics, but not to the level of determining valve events that are best suited to a particular application. In the table below, I have bolded the cams that seem like a good match for my goals. Which would you choose to have performance equal to or better (for a heavy truck application) than the Low Buck Truck, but with a more civilized idle? What others have I missed? Even general guidance would be appreciated.
Absent any other info, I'm leaning toward the Titan 2, though I'm at the minimum recommended compression ratio. Mostly due to the exhaust duration compared to the others. 2nd choice would be the Summit one.
You’ve already done a good job organizing the options by duration, LSA, and overlap, and narrowing down the ones that match your goals. The two you're eyeing are right in the window we’d be looking at, based on what you’ve mentioned you want out of the cam swap.
Since your chart focuses on duration, LSA, and overlap, the next step is translating those specs into valve events. Below are the valve events calculated at .050" lift, so we’re comparing everything on the same standard.
SUM-8719R1 .550/.550, 209/217, 112+1 with -11* of overlap
IVO: -7* BTDC
IVC: 36* ABDC
EVO: 41* BBDC
EVC: -4* ATDC
Valve Events Explained:
EVO (Exhaust Opening) EVO controls how the cylinder evacuates combustion gases, also known as blowdown. Most blowdown happens before BDC due to remaining cylinder pressure, so opening the valve earlier or later is a compromise.
Opening the valve earlier creates better evacuation and less pumping loss on the piston upstroke at high speed. This will help top-end power. Opening the valve later helps low-end performance, keeping pressure on top of the piston longer. This also reduces emissions. However, any positive pressure on top of the piston at BDC costs power because the piston is pushing against crank rotation.
IVC (Intake Closing) IVC has the biggest influence on where the powerband lands. It affects engine behavior more than any other valve event.
Closing earlier builds more low rpm cylinder pressure and torque. Closing later shifts the torque curve higher in the rpm range by using the inertial charge longer after BDC.
IVO (Intake Opening) IVO is the starting point for the air/fuel mixture entering the cylinder. It primarily controls the idle quality but also has an effect on top-end power.
The earlier you open the intake, the choppier the idle.
The longer the intake valve is open, the more air/fuel you can get in on the downstroke. This comes at the expense of idle vacuum.
EVC (Exhaust Closing) EVC largely determines overlap. Closing the exhaust valve later increases overlap.
Overlap can help scavenging in very free-flowing, well-matched exhaust systems. In most street or full exhaust systems with manifolds, converters, and mufflers, extending EVC too far increases the risk of exhaust reversion and can hurt idle quality and drivability.
How This Applies to Your Combo:
The Low Buck’s 33* IVC is a big reason it feels strong down low in a heavy truck. The 4* overlap and tight 107 LSA are what give you the lopey idle and likely contribute to the rotor rattle.
The Cam Motion Titan 2 (CXM-03-01-0199) keeps IVC nearly identical at 34* ABDC, so it should feel very similar off-idle and through the lower rpm range. It also reduces overlap and opens the exhaust earlier at 46* BBDC, which helps idle stability and can improve how the blower carries at higher rpm.
Our SUM-8719R1 moves IVC to 36* ABDC. That’s only 2-3* later, so we’re not talking about a big loss of low-end torque. It will give up a little off-idle and low-end compared to the Low Buck and Titan 2, but it’s not going to feel like a tow truck next to an F1 car. With your planned 2,800 rpm stall, that slight shift in the torque curve becomes much less noticeable and can actually work well in a heavier truck.
Given that you’re rebuilding the short block and considering a converter change, our SUM-8719R1 is a great fit for a smoother idle while still maintaining strong street manners. The Titan 2 remains a strong option if you want to stay as close as possible to your current low-end power while carrying up top better than the Low Buck.
For a visual, check out this video on valve events and how they affect engine performance:
@Summitracing
Thank you for taking the time to provide a detailed response! I very much appreciate what you do for the community here, as I'm sure others do as well. I always learn a lot from your posts.
As far as the cam goes, it doesn't sound like there are really any PD-specific aspects to consider, which I'm not totally surprised by. Richard Holdener, when asked about blower cams, always says that a cam will do with a blower what it does NA. While that does seem to hold true, that's not exactly what I'm asking. I was curious to know if there were any things to consider to be better for a blower application than using a standard NA cam. It seems like all the blower cams are just designed to shift the powerband to the right to soften the low end. Initially, it looked like the LS9 cam would be a clear winner in my application (smooth idle, same lift, designed for a blower) until I saw dyno graphs of the powerband! I didn't realize that the long durations and wide LSA were for higher RPM performance. It's probably a good street cam, but definitely not great for a truck that is actually used as a truck.
Any others to consider, given my constraints (smooth idle, keep current beehives, truck-like powerband)? Sounds like there may not be much benefit to spending time considering many others if I'm already over the target.
We appreciate the kind words. Glad our posts have been helpful.
You’re right that a cam generally does with boost what it does NA. However, in a PD blower application, especially in a truck used as a truck, there are a few things we pay closer attention to.
Overlap control
With a roots-style blower like your M122, you’re already forcing air into the cylinder. Excess overlap in a full exhaust street truck often hurts idle stability and increases reversion more than it helps power. It also increases uneven intake and exhaust pressure pulses at idle, which can contribute to the rotor rattle you’re trying to clean up.
Exhaust blowdown under boost
Earlier exhaust opening gives more blowdown time. Under boost, cylinder pressure and backpressure are higher, so giving the cylinder more time to evacuate helps it carry power better at higher rpm instead of feeling like it tapers off.
IVC and torque placement
IVC largely determines where the powerband lands. Earlier closing favors low rpm cylinder pressure with a lower powerband. Later closing shifts the curve to the right. In a truck that’s used like a truck, staying in the mid-30s ABDC keeps it feeling responsive unless converter and gearing support moving it.
Between the Titan 2 (34* IVC) and our SUM-8719R1 (36* IVC), you’re looking at a 3* shift. That’ll make a slight change where the power comes in, but it’s not like a tow truck compared to a racecar.
Both cams reduce overlap compared to what you’re running now, which will improve idle quality and help limit reversion and pressure pulses that contribute to the blower noise.
If the stock converter is staying for a while, the 34* IVC of the Titan 2 will feel a little closer to what you’re used to. If the 2,800 stall is going in, the 36* IVC of our SUM-8719R1 makes sense because the converter will help mask that small shift and let the engine operate where that cam is happiest.
At this point, you’re already in a narrow window. There isn’t a hidden magic cam that’s going to suddenly transform everything without some trade-off. Both cams being discussed are great options for what you're trying to do. It just comes down to your priorities for the combo.
Let us know if we can be of any further assistance. We’ll be happy to help.
Help with cam selection for PD blower 
