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Help selecting cam for 6.2 L9H with a Maggie

Old 03-17-2019, 11:32 PM
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Default Help selecting cam for 6.2 L9H with a Maggie

Hey guys! I'm new to the site, recently slapped a Maggie on my Sierra last month. I've been a drag racer for years, but am new to forced induction and trucks. Most of the stuff I've worked on in the past have been NA LS motors. I've been reading through the forum to learn as much as I can and have gotten a few ideas about what I want to do with the truck, but would definitely appreciate your input before I start buying parts. My setup so far is:

2012 GMC 1500 6.2 flex fuel (L9H) with NHT towing package
Magnuson TVS1900 kit with the 3.3" pulley that Maggie claims makes 6 PSI
Dyno tuned (sheet below)
180* Tstat
3.73 gears and 31.7" tires
Not my daily driver, but used to tow a 8000 lbs trailer a few times a year and to go on long road trips
Goal is for it to be reliable in 110 deg summer while towing, be able to pass with a trailer, and be comfortable while cruising on the highway.

It made [email protected] rwhp & [email protected] in 3rd gear on the dyno after the tune. I thought I would be happy with these numbers, but honestly was a little disappointed after I tried passing while towing with it (it's great without the trailer). I guess I was expecting more, and after talking with the shop that did the install they recommended adding longtubes with high flow cats. This sounds reasonable to me, and if I get them ceramic coated should help keep underhood temps down. He did say it would need to be retuned and I figured I might as well do some other upgrades once I'm at it.

My thoughts are to go down to a 3.2 or 3.1" pulley and swap in a cam while doing the headers and retune, might need to go up on the injectors too depending on the IDC(not sure what they're at right now). From what I've read so far a wide LSA and negative overlap is good for making power with a blower, but also increases cylinder pressure and piston top heat. I'd like to find a combo that will work well together to make more power in the midrange for passing under load. The factory cam in this motor is a 198/209 .500/.500 on a 115 (don't know the overlap), and the peak HP and TQ are in a pretty good location (dyno sheet below). I was thinking of splitting the difference between it and the LSA/LS9 cams, something like a 205/223 .550/.550 on a 120 with maybe -5 overlap. I have no idea of this is a good choice given the 10.5-1 compression, max of 8 psi boost that I want to run, and still be able to pull my trailer in 110* heat without crazy high IATs/cylinder pressures. I realize that this is not the most cost effective way to produce max HP, but as I stated before I'm looking for the combo that will give me the most HP under the conditions I stipulated above and have no intention of racing the truck. I'd really appreciate your thoughts and suggestions!


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Old 03-18-2019, 08:34 AM
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the cam specs mentioned above has a lot less overlap than -5.

I would do something like this: 220/236 117+5

It will have plenty of meat under the curve while keeping your peak numbers close to where they are now. I would guess you could spin it to 6400 if you wanted to at the track.
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Old 03-18-2019, 11:54 AM
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Are you still on factory injectors? You're probably maxed out as is.
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Old 03-18-2019, 02:56 PM
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Yes, still on 54 lb injectors, didn't use the 42 lb ones that came with the kit. Tuner said the IDC was fine, but I dont recall what the value was.
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Old 03-18-2019, 03:09 PM
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Thanks!

I haven't plotted out the specs on valve openings/closing on a cam card yet, but your probably right about the overlap. How much overlap should I be shooting for?

Excuse my ignorance, but 220/236 is a little bigger than I would've chosen for an NA truck motor. I realize the wider LSA and advance will help with idle and broadening the torque curve and the blower pushes the whole curve up. Typically want more exhaust than intake duration on most motors, but especially with a superchargers/turbos. Does the blower also help with lowering the peak HP/TQ values compared to an NA motor with the same cam duration? Trying to learn why you picked those cam values.
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Old 03-18-2019, 04:30 PM
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Blower's like his TVS1900 inherently make low end power extremely well. Even with the "larger" cam his torque will be damn near at its peak by 3500RPM. The larger duration numbers and wider LSA help the blower carry that torque curve longer than the stock cam will.

You are correct, that is slightly "larger" than I would have gone for an NA cam. NA this particular cam would feel kind of doggy compared to a dedicated NA cam that has the same end goal - usable power for a truck.
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Old 03-18-2019, 06:17 PM
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Call a company and have one spec’d for your setup. Brian Tooley Racing or cam motion both offer pd blower cams off the shelf.
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Old 03-18-2019, 06:50 PM
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I was on BTR's and Cam Motion's websites looking at some of their cams. The off the shelf PDS cams looked big to me for my intended purpose of towing, better suited for a Camaro or CTS-V that wanted more power. The centrifugal cams looked more reasonable, but I didn't know if that style of grind would work as well with a Maggie. I wanted to get some opinions on here to get an idea of what range I should be looking for before I order a cam. Vortec350ss posts were really helpful.

From what I've read, BTR seems like a reputable shop. Would you recommend them to do a custom grind? I've typically used CompCams in the past since I've had really good results with their lobe profiles on my NA motors. But if they have better grinds/lobe profiles for supercharger applications, I'd be happy to try them out.
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Old 03-18-2019, 08:44 PM
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BTR is great company all around. Great product and good customer service so you cant go wrong. Just give them a call they may have something smaller for you or can spec something out. Cam motion is also great to deal with. Cant go wrong with either one honestly.
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Old 03-18-2019, 10:21 PM
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what about lengenfelter gt2-3 cam 207/220?? or a vinci ultra torquer 210/218

i am interested to see where this goes. I have a 2001 2500HD CC 6.0 Magnuson supercharged at 5 psi stock motor (362 rwhp/404 rwlb) westers mail order tune, towing closer to 10k and want the same thing you do. I am putting in 4.88's to pull the Cascade mountains and not have to drop to second gear at 50 mph.

Last edited by tglandon; 03-24-2019 at 10:59 PM. Reason: wrong mph
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