bolikes2skate

I was just wondering why the 99 model 4.8 makes the least amount of power?
255hp if im correct and 2000 and later make 270hp?? whats up with that?
the compression is 9:5:1 on both..same head casting number..same valve sizes.. same bore/stroke.. pretty sure the cam has the same specs on both years. Is the difference in the tuning? was the factory 99 model tune just very conservative? i got the 99 model and would like to make that power my year model lacks. 15 horses would make quite a difference. Thank You in advance.

00ChevyScott

iTrader: (10)

cam specs are slightly different, and the tune might be more conservative. Also the hp rating might be at a different RPM level.

bolikes2skate

thanks for the reply. i didnt know the cam specs were slightly different that would make sense. both are rated there hp at 5200rpms.

BlackGMC

iTrader: (31)

They have smaller injectors, the factory 99 OS sucks, IMO it is in the tune... This is why people upgrade the injectors and to a 02 OS...

_zebra

iTrader: (5)

does that go for the 5.3 as well?
i'm fixing to do a 4.3 -> 5.3 swap & found an 02 engine. i'm assuming that would be better than a 00-01

budhayes3

iTrader: (19)

All that and a slightly different cam...I know that the LSA was different but can't remember the rest of the specs. I replaced my 99 PCM and injectors with 02 stuff

chevyz7120

iTrader: (1)

and it made a bigger difference when u swapped to the 02 stuff? cuz i got an 99 4.8l z71 and it seems pretty slow for that v8 haha

budhayes3

iTrader: (19)

Well, I did a cam swap first (baby cam in my sig), and couldn't get it to run for **** with the 99 stuff, I got 7.9* of KR (knock retard) every time I tipped the throttle in...false knock actually, part of the issue with the 99-00 PCM. Just swapping the 02 stuff in, un-tuned allowed the truck to run great. After getting the PCM tuned it ran excellent If you're planning any performance mods, swapping to an 01-02 operating system and at least 00+ injectors is a must IMO.

chevyz7120

iTrader: (1)

i dont mean to steal this thread from anyone lol but wat all do i have to replace to get the 02 setup?

budhayes3

iTrader: (19)

If you have a 99 you'll need injectors from an 00+ 4.8,5.3, or 6.0 (non flex-fuel), they're all the same...I believe that they're 24.7#. If you're a 00 you already have the bigger injectors

As for the PCM, you can re-tune it if you have software like EFILive or HPTuners, or have one of our sponsors such as BlackBear, Wheatley, or Nelson tune it for you.

Back when I did mine we were still figuring this stuff out and I ended up replacing my PCM with a different 02 unit, along with changing the alternator to one that was compatable with the PCM and running a wire from the PCM to the alt. Since then the tuners have figured out that it's easy enough to just flash an 02 operating system into your current PCM and I suppose they can turn off the monitors that would throw a blinking battery light that I had after swapping in the PCM. I believe that's how it goes...