Looking for a little more towing power up to 4k rpm. Concidering rehabing the 125k 5.3 with 4.8 pistons and an LS1 cam (99-00 12560965 198/209 .500/.500 119.5) and advance it a couple of degrees to push the power band lower. I've got some 918 springs coming. Most of the truck's use is daily driving but a few times a year the #5500 TT gets hooked up and we pull 800 miles one way. For the most part its fine, I just want a little more. Ive got a wait 4 me tune and gibson shorties otherwise its stock. I thought about a freer flowing exhaust but at the rpms I run I doubt I would see much gain. If this one rots out I'll upgrade but not before.
Any thoughts on what amount of increase I would see in the power band from 2 to 4K?
Thanks,
Bob

 

pistons are the same, cam is a waste for what you are trying to do... LS1 cam isn't built to tow... gibson shorties are a waste of cash also...

if you had any asperations of motor work, just get a 6.0L short block and a small cam (not a stock LS1 cam or LS6 cam either... not for grunt) and throw that in with a set of real headers...

 

Yeah, the gibsons have been on for years and they are not worth the effort it took to put them on but I have them so they're staying. A 6.0 would definately give me all I need and more but I don't want the day to day penalty in mileage. That cam looked like it could work for me with the moderate lift and duration coupled with the wide LSA for very little overlap. That cam makes good mid range power and I thought advancing it would help push the power band lower in the RPM range. Thats my reasoning anyway. I very well could be wrong.
Bob

 

i thought the 4.8s had flat topped pistons?

 

means same bore... my bad... basically it would be a monumental and legendary waste of money, time and effort to do the mods you mention here, especially with the goals you have for the mods.

 

The 4.8 flat top pistons would up compression considerably.

I've read the 4.8 pistons will work, and I've read they wont, so it's a toss up on that issue.

But if it will work, I would do the 4.8 pistons, stock heads, ls6 springs, a 208/212ish cam, and some long tubes and supporting mods.

 

the stroke and rod length of a 5.3 are different than that of a 4.8, so most likely the pin location is different between the two also, however I could be wrong.

 

I have seen a few people calculate it, and depending how you round the numbers it comes out to the same or different by .003". So it is very close and really depends on how you try and calculate it.

 

the last time I saw the numbers it was something like .025" difference between the rod lengths... thats more than I prefer to gamble with, now if it were 3 thou, thats getting closer to reasonable range.

 

dont let MPG hold you back on the 6.0 swap, you wont notice but a 1-2mpg, IF ANY...
plus it leaves plenty of room for improvement...