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Previously stock 2007 GMC Sierra Classic with a 5.3 L33 engine in it that I bought new and currently has 198,xxx miles on it. While having the cam replaced I replaced the springs, lifters, installed a trunion upgrade kit, added an Airaid tube from the stock air box and had it dyno tuned. Unfortunately I didn't put it on the dyno before I had the work done. I was expecting +/- 20 more horsepower and +/- 20 less lb/ft torque. What do the experts on here think?
If you look at the "valve events", it doesn't change the IVC point much, if at all compared to the previous camshaft. That alone should tell you not to expect too much of a gain in peak horsepower since the IVC point is the single most important factor. This seems like a cam with more "area under the curve" in mind.
If you had an adjustable cam gear, you could probably retard the cam a little bit and see the power band move up, giving you a little bump in horsepower at the expense of low end torque.
The more I research it the more I think the horsepower is lower then it should be I will stop by and talk to my tuner next week and see what he says. I wonder if the cats are clogged or if the tune is to conservative or something total different. Does it make any sense that it seems to be getting stronger as I put miles on it since it was tuned? I've read about oiled filters causing the MAF sensor to be off and I have a 10+ year old K&N on it. Could that be a problem? What else should I check?
68Formula - Thank you for your input. The truck is tuned for 93 octane so unfortunately I can't bump that any more. My plan is to install LTs in a couple of months and maybe a catback at the same time. My truck has always done what I've needed it to do I am just trying to make it a little more fun in the process.
Tech@WS6Store- That's a lot more then I will every tow with this truck the heaviest toy I move on a semi regular basis is a Kubota L39 which weighs about 7,000 pounds. I took this picture off the internet it's very similar to my set up. I will be moving mine about 2 hours away as soon as we get some dry weather and I am looking forward to seeing how the truck pulls it with the new cam.
If you look at the "valve events", it doesn't change the IVC point much, if at all compared to the previous camshaft. That alone should tell you not to expect too much of a gain in peak horsepower since the IVC point is the single most important factor. This seems like a cam with more "area under the curve" in mind.
If you had an adjustable cam gear, you could probably retard the cam a little bit and see the power band move up, giving you a little bump in horsepower at the expense of low end torque.
Yes, the 8718 cam has the earliest IVC event in our truck lineup at 33* ABDC. This was designed as a towing/efficiency camshaft.
About the best thing you can do for towing is the stock cam imo. Then throw some 1.8 or 1.9 roller rockers on it with some valve springs. Ls6 springs are probably fine. Adding rocker ratio tends to aid tq in the low/ mid range. Couple that with some headers and that combo picked up my uncles 4x4 5.3 .3-.4 in the qtr.
Drivability was greatly improved as the truck doesn't downshift or unlock the converter going up mild grades anymore. It even picked up about 1mpg.
The stock catback is holding it back a bit now and probably the stock intake system.
The more I research it the more I think the horsepower is lower then it should be I will stop by and talk to my tuner next week and see what he says. I wonder if the cats are clogged or if the tune is to conservative or something total different. Does it make any sense that it seems to be getting stronger as I put miles on it since it was tuned? I've read about oiled filters causing the MAF sensor to be off and I have a 10+ year old K&N on it. Could that be a problem? What else should I check?
68Formula - Thank you for your input. The truck is tuned for 93 octane so unfortunately I can't bump that any more. My plan is to install LTs in a couple of months and maybe a catback at the same time. My truck has always done what I've needed it to do I am just trying to make it a little more fun in the process.
Tech@WS6Store- That's a lot more then I will every tow with this truck the heaviest toy I move on a semi regular basis is a Kubota L39 which weighs about 7,000 pounds. I took this picture off the internet it's very similar to my set up. I will be moving mine about 2 hours away as soon as we get some dry weather and I am looking forward to seeing how the truck pulls it with the new cam.
I do tow less, but giving you an example of the cam to choose based off what i do and say not just what someone says but never does.
Real world experience and info will tell you alot more than calculators and text.
Don’t listen to anyone recommending a stage 2 218 cam for constant towing with a 200k mile 5.3 that needs to pass emissions and won’t have a harsh effect on fuel efficiency. That not going to work and you are on the right track.
We recommend removing tq management, but there is a caveat. It can be hard on your transmission if it’s at capacity, but trying to improve tq while removing it through the Ecm isn’t going to work either. Monitor trans temps.....that’s why GM put to management in place to begin with. Let it eat and add more trans cooler capacity as needed.
Last edited by Summitracing; 02-22-2020 at 01:39 AM.
Not sure where you get that from, but that stage 2 cam is perfect for all of what you just said. It can pass emissions, works well for towing, and have 0 issues on the truck itself. I have 2 of them. One in each of my 2500hd trucks and love them. Great power, great drivability. One had 129k on it when i installed cam, the other had 217k. My 05 xcab 4x4 has 357k on it now and is running flawlessly.
OP maybe you should listen to someone that does the testing in real life daily?
I also have an 08 nnbs tahoe with 5.3. Guess what cam is going in it when i dod delete it? Im pretty sure you can guess.
Its a great cam for trucks that dont want a converter, want an easy daily and want to make the best power for the price spent.
After installing them in my own personal trucks along with countless others in customers and us tuning them in house along with quite a few other friends and business i stay in contact with doing so, id say that point to a win in the truck cam column. Thats quite a broad spectrum and also shows i use my trucks quite a bit more than most and still have 0 issues.
A 218 exhaust lobe isnt going to be the issue with a cam. Especially if you dont know any of the rest of the specs.
The 8718 in this post is 1* off. Itll make THAT much of a difference. Not likely.
After installing them in my own personal trucks along with countless others in customers and us tuning them in house along with quite a few other friends and business i stay in contact with doing so, id say that point to a win in the truck cam column. Thats quite a broad spectrum and also shows i use my trucks quite a bit more than most and still have 0 issues.
A 218 exhaust lobe isnt going to be the issue with a cam. Especially if you dont know any of the rest of the specs.
The 8718 in this post is 1* off. Itll make THAT much of a difference. Not likely.
We respect you for for certain but it’s not the exhaust lobe we’re talking about. It’s the 205 intake lobe with 33 degree intake closing point for torque and efficiency vs even our own Sum-8701 or Sum-8720 that we wouldn’t recommend for his application.
video shows how bad a 211 degree intake duration Ls9 cam can be for torque at 3k vs a LQ9 cam for instance. An excellent primer on where torque and power shifts with added cam timing. Note, the super wide ls9 cam LSA isn’t helping matters, it’s an example of why individual valve events need to be put where they need to be.
Last edited by Summitracing; 02-23-2020 at 11:16 PM.
Thats not the just intake lobe doing that. And its also low lift.
Ive posted this too many times but here is the cam i was talking about
Your emphasis was also all on the 218 thats why you said 218 cam.
Here is the graph on a 5.3l.
This is the difference in low lift vs high lift and why higher lift will gain, period. And also why the tsp stg 2 high lift is the perfect cam for what nearly everyone that goes with a smaller cam is looking for. Direct example done by the cam grinders themselves and definitely NOT a ringer either. There is plenty of tuning left in all of their setups that they dyno for shelf cams.
Thats also with an nnbs/tbss intake and 92mm tb so its possible a std 5.3l would see better torque down low.
This is also why ill never use nor recommend a low lift cam. Its definitely not the optimal cam in any situation. Budget is the only reason to look at a low lift, but anyone can save more for better springs so its really a moot point then.
I think the tune is far too conservative. You can still squeeze more power out of your current combination by modding your exhaust, porting heads, and tuning the truck yourself. You don't need high lift or more duration to get more power out of your 5.3. You're still leaving power on the table with the combo you have. Just to give you some ideas: tune the 5.3 yourself, use thinner head gaskets for more compression, hand port your 243 heads (I hand ported my 799 heads), run copper spark plugs, etc.
Ws6store, your graph has the smallest 212 cam (both high and low lifts) coming in #1 and 2 for bottom and midrange torque. A 205 would be even stronger down low and that dip in the 3000 range wouldn't be there to that extent. The 216's aren't passing until what appears to be 4500 or so, but the bottom of your graph is cut off.
The SUM-8718 tow cam is designed to be the cam the trucks should have come with at the factory. Literally for contractors etc. looking to go another 150k miles without beating up the valvetrain and wanting to maintain good fuel efficiency. To get .600 lift out of a cam that short in duration is using very aggressive ramps. We have two other stage 1 and two more stage 2 truck options, but that's not what the O.P. needs for power in the 2200-4000 range.
Don’t listen to anyone recommending a stage 2 218 cam for constant towing with a 200k mile 5.3 that needs to pass emissions and won’t have a harsh effect on fuel efficiency. That not going to work and you are on the right track.
We recommend removing tq management, but there is a caveat. It can be hard on your transmission if it’s at capacity, but trying to improve tq while removing it through the Ecm isn’t going to work either. Monitor trans temps.....that’s why GM put to management in place to begin with. Let it eat and add more trans cooler capacity as needed.
Most of the 6L80/90's shift better leaving the tq mgmt somewhat enabled, you can cut it down to 15-20% and you can also adjust how much timing it can pull when enabled.
Most of the 6L80/90's shift better leaving the tq mgmt somewhat enabled, you can cut it down to 15-20% and you can also adjust how much timing it can pull when enabled.
Good info, thanks for posting. That sounds like a good move for traction under certain traction conditions.
02-21-2020 | 11:49 AM
