How much power will my truck make after these mods?

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Tonyrodz

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Something else to consider thru all this. As you continue to do this horsepower increase and if you go even further, you need to make sure some other systems are up to ***** for the increase. First in line is brakes, you can go fast but you gotta STOP. Next is steering and suspension, so that the handling can be safe during the HP runs. Make sure the cooling system is clean and flowing great and being cooled properly. Is the transmission in great shape and do you know when the last time it was serviced and what was done during that servicing. Rear diff comes to mind. Fluid condition/age and gear lash and sight inspection of the guts.
Excellent point. After my cam/motor install the 1st thing to go was the trans. Couldn't take it lol. Our transmissions aren't known to handle a lot of power stock.
 

MassHoe04

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I would really love to do any or all of the above-mentioned performance mods!
Then, back to reality for me.

I think of having to do things like front CV axles and whatever else might come up that is needed to keep it on the road.

The thought of spending thousands for performance mods on a 207k+ mile truck, only to risk blowing up something critical... Just something I can't even think of risking.

Maybe someday, I'll have enough money to play with for fun, instead of always having to grind just to hold things together.

I do enjoy seeing all the cool and fun things many of you are out there doing. Appreciate all the interesting write-ups and ideas! Keep'em coming!
 

Rocket Man

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The tune is the only thing on that list that will make much difference and if it was my money, that's the first thing I would do. Shortys don’t do a thing on these trucks, and the exhaust will just make it sound better. A cam is the next best bang for the buck and can net quite a few hp depending on which one but if you’re gonna do that, do it before the tune or have provisions to update the tune via an Autocal or similar since the tune will have to be adjusted for the cam. Like others have said, the trans needs to be fairly solid or else it won’t last long after you start adding power so just keep that in mind- you can’t just start beating on it or it will fail if it’s weak.
 

Donal

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Ok so I have a 2002 GMC Yukon 5.3 LM7, I think the stock power rating is 285?, Where do you think I'll be with a few bolt ons like, Shorty Headers, High Flow cats, catback exhaust and a blackbear tune?


145k Miles.
If the vehicle has the "Tow/Haul," function, drive in the tow function for a few days and the engine will be up the horsepower curve a bit and see if you like additonal performance. You can keep a log of the rpm range that you use daily in standard mode and then in Tow mode. Then you will have a the RPM range to target for improvement.
 
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Alex_M

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In truth, if you're wanting more of a kick in the pants on the street then you might just look at regearing the truck. A lower ratio (higher numerical number) differential gear will net your drive peppier on the street more noticeably than any of the mods you mentioned.

Torque in the lower RPMs is more what makes your vehicle feel peppier on the street, not horsepower (at the higher RPMs) as much. This is an oversimplification as both are measured across the entire RPM range, but generally gets the point across. The lower gearing will give you a bit more mechanical advantage and give you more effective torque output at the wheels.

There are a couple cam options that will keep the low end torque for the street and add some horsepower on top, but you'll only feel the difference if you're revving your truck out regularly. If that's something you're interested in then the Richard Holdener recommendation is a good one. Pay close attention to the RPM range you usually drive in, and what RPM range his tests show power gains (and losses). As a general rule of thumb, you will barely notice any difference if any at all at less than a 20hp gain. For a noteworthy "seat of the pants" gain, you're looking for 30-40hp gains.

The 15-20hp gain estimates with tune, shorty headers, exhaust, are roughly accurate. Most will be on the lower end of that spectrum, and all the gain will be in the higher RPMs. On the street in your normal RPM range you will get 0-5hp gain (from the mechanical upgrades, talk about tune further down) due to the air flow demand being lower. Removing your catalytic converters or going to a "high flow" converter will net you zero gain. All modern catalytic converters are "high flow" since the mid-90s, and do not provide a noticable change until you get in the 600-700hp range. In fact, with aftermarket converters you may actually impede the exhaust flow due to the transition between the straight pipe and the new converter (again, a near immeasurable amount) not being as smooth as that to and from the factory catalytic converter, and creating turbulence in the exhaust system around those transitions.

Making notes on the tune specifically, you are not likely to unlock much extra horsepower from a mail order tune, but will notice some seat of the pants improvement for the same reason you will notice an improvement with a gearing change. The tuners generally change your transmission shift pattern to hold the truck in a higher RPM range making more effective use of the power at the trucks disposal. If you get a talented tuner to tune your truck in person, there are a few stray horsepower that can be unlocked.

So in summary, your most noteworthy return is probably going to be a gear change plus a tune. Remember if your truck is 4wd, you need to change the front differential gears at the same time.
 
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