Performance adders

2003GMC5.3 · July 16, 2005

Hello, everyone i am new here. i was wondering what i can do to add some performance as well as fuel mileage. So far i was thinking of adding a cold air intake, pulleys and an intake spacer. It is a 2003 GMC sierra with the 5.3 engine. Any help would be appreciated thanks

Chronic · July 16, 2005

Modify the exhaust system to complete the breathing and fine tune with a programmer/replacement pcm.

MrQuadrasteer · July 16, 2005

Welcome to GMT

First, don't waste your money on a spacer.

Next, your FIRST mod should be a custom tune (Wester's ). It'll absolutely give the best bang-for-the-buck It'll compliment just about anything you can do to your engine, and most tuners offer retunes for cheap or free.

Use a cooler t-stat with your tune.

Electric fans will also free up a lot of power and reduce strain on the engine.

A good cold air intake (aFe ) will allow the engine to breathe a little freer.

Pulleys are okay.

The factory exhausts are actually pretty nice from the factory. I remember reading at LS1Tech (before they changed to PerformanceTrucks.com) that the most that could be gained from a cat-back on our trucks was around 5hp. The main reason to swap cat-backs is look or sound.

But add headers to the cat-back, and you'll really notice. Stay away from short-tubes.

All of the above would probably give 75hp or more.

But the custom tune alone will make about as much difference as all the other items combined.

vhato · July 16, 2005

I agree with MrQsteer,

A custom tune is the first place to start. That will give you the most power/efficiency per dollar. If you insist on a HandHeld Programmer then I would go for the Predator even though the custom tune will give better immediate results. If you want your truck to sound strong, get a cat-back followed by an Intake.

Chronic · July 16, 2005

What exactly is a cooler tstat? Where would you get it? Would this void a warranty? Wouldn't headers void a warranty?

MrQuadrasteer · July 16, 2005

T-stat=thermostat

Our engines have reverse-flow cooling systems (as opposed to first gen small blocks), so a cooler stat *should* help keep the heads cooler, thus prevent knocking longer.

In reality, just swapping the stock stat and doing nothing else won't make much difference.

If you have a mechanical fan, you'd need to swap over to electrics (or are different clutches available ??)

If you have electric fans, you'd need to change their on/off points.

Having said that, I have a 187* in my truck and saw about a .05% change

When I get my e-fans, I'll swap in a 160* stat, have on temp of about 175 and off temp of about 160.

If you swap stats, make sure you're tuned for it, or the engine will never come out of cold-loop. It'll kill your mileage, wash-down your cylinders and run too rich.

vhato · July 16, 2005

T-stat=thermostat

Our engines have reverse-flow cooling systems (as opposed to first gen small blocks), so a cooler stat *should* help keep the heads cooler, thus prevent knocking longer.

<{POST_SNAPBACK}>

Holy Crap,

I didn't know that. I thought only the LT-1 and LT-4 were reverse flow. I am glad to hear this. Believe it or not, I just a$$umed GM went back to the old style and I didn't even look. Kudos to GM for doing it right.