Ok hear is the deal. I just got a 2004 Gmc 5.3 and I want to get more performance out of it. I already have a K&N GII, and a borla exhaust. I have some Gibson shorty headers and an ASP power pulley ready to be installed. What else should I do to get better performance out of it, should I try selling some of the stuff I already got to get something better ? Some of my friends tell me to get some gear's, my truck came stock with 3.42 limited slip. I was thinking of getting some 3.73's or should I go with the 4.10's ? Please help ! Thank's. . .

 

welcome! These motors do see nice gains with bolt on mods like you have, but if you have your truck tuned for it you will swear your driving a different truck. I suggest a Nelson tune. Ive heard he is the best right now, and you will see huge gains. Your current mods are all good ones and will make for a quick truck.

If you do swap gears i say 4.10s. My truck stock w/3.73s got 16mpg, and w/4.10s and all my mods i now get 17mpg. Cant go wrong there.

Where are you from? If you can get rid of the cats and you will gain some more power too.

 

also sell the shorties and get some long tubes you will see better gains with them

 

dont forget to look into upgrading you transmission internals w/ a shift kit and servos... that nelson tune is gonna give a beating.. heheh.

 

Pull the heads and have then CNCed and throw in a cam while your at it. Then install some CC Pro Mag 1.85 rockers and hardened pushrods before you put the valve covers back on. You better put in some CC 918s for the new cam and rockers too. You might as well install a double Rollmaster and ported LS6 oil pump before you put the timing cover back on. You can gut your cats with a plumbers snake chucked up in a 3/8 drive electric drill, but you'll need to get some 02 Simms or LS1 Edit if you do that. Then put on a Meziere instead of the stock pump and some electric fans. I might have left something out, but I can't think of anything more right now. Be prepared to make more frequent stops at the filling station.

 

Damn, he just wants a little more power, not a top fuel dragster

 

Yup.. sell you Gibson shorties. They are proven 4-5 rwhp. Get some mid-long tube header and you will feel a big difference from the shorties.

 

 

Yah well I'm gonna try looking into the long tubes, the reason I got the shorty's is cause I used to have a 99 silverado 5.3 and they came off of that. They made a big improvement on that from a 15.74 to a 15.39 so I'm really looking forward to getting some longtubes. So you guy's think the 4.10's won't destroy my fuel economy ? Right know i'm getting a good 16.5 mpg so if it stays around that area and get better performance I think I'd go with the 4.10's. . .

 

I'm from Texas but I travel back and forth from Washington. I'm pretty knew here but you may know some of my friends that are in my club (I8AHEMI), (JoeJoe).
By the way what exactly is a nelson ? Sorry guy's i'm not too familiar to all of this stuff and I'm trying to learn more. . .