Has anyone ever dynoed a 5.3 liter v8 chevrolet engine? Was wondering how much you can actually get out of a dyno or a custom tune and if it is really worth it.

 

i think the usual # on a dyno is 235-245hp to the wheels.
and yes a custom tune is always worth the money if done by a competent tuner.
i would suggest justin @ blackbear performance.
he said he typically sees 25-30hp to the wheels on my 6.0 LQ9.

normally a 20% loss is common for an auto transmission.

the main thing for your 5.3 would be to remove about 80% of TM and have abuse mode removed/adjusted. also if your gears can help/hurt performance as well.