What do the newer 5.3's have that the older ones dont. Why is the newer engine rated at 315hp,295hp, but 99 is 270hp, and then it is 285 for a few years?? what gives?

 

 

i think its the heads

 

Heads, Pistons, compression ratio, camshafts, tuning....depending on which 5.3 you refer to.

 

yea... i still havent figured that out for my 4.8 yet either. mine was rated at 255hp 285tq and somehow they are up 40hp 20tq since then. the cam changed but not enough for 40hp.

 

the tunes are quite different from what I've seen comparing stock tune files from the HPtuners repository. I know the L33 is aluminum, but I'm not sure if it has the same cam or tune.

 

also, efans play a decent role in the power difference.

 

efans have nothing to do with the factory rating

 

compared to the older motors yes it does. The 99-04 trucks had a belt fan while the newer trucks (not all of them) have stock efans increasing the HP. There's other factors that add hp too, but this helps a bit. I think the WT trim trucks still have the old school fans.

 

They are rated more....but feel like they have less hp when going from a 99 up to a 04...atleast from my experience. Maybe they put more TQ management on them???