I have a little bit of a dilemma. In my possession I have a 2001 Tahoe with the 5.3L and a 2008 Silverado regular cab with the 4.8L. The engines will be staying in their respective vehicles. I was doing some research between the two and found out that my 4.8 has a bigger throttle body and has the 799 heads. I noticed that the rated horsepower was around the same for both engines. Basically what I want advice on is if I were to theoretically FBO both engines identically in addition to a cam what engine would have the most potential? Is the 4.8L modern enough that the displacement differences are don't matter or does the older 5.3L have greater potential? I'm not that knowledgeable of the differences between the two generations so any advice is appreciated.

 

While the HP may be close to each other, the higher displacement engine yield more torque (especially on the low-end.) Generally, the larger displacement, the easier to get to targeted "X" HP or TQ. For a full sized heavy vehicle, the larger is what I would select.

But you can take the 4.8 and swap the rotating assembly (pistons, rods and crankshaft) from a 5.3, assuming everything checks okay like bore-to-piston clearance. The 4.8 and 5.3 were same bore, just shorter stroke on the 4.8.

Maybe you can tell us what your goals are for these vehicles and someone can offer good advice. Are both engines running good? Just overhaul the engines and want a reliable daily driver? Any towing/hauling? Or weekend fun vehicle?

 

The goals for the vehicles were just as a fun weekend ride. Both engines run good, but the rear main seal on the 5.3 does need to get replaced. I've been looking at wanting to cam whichever engine and putting long tube headers on in addition to an exhaust. I won't be towing anything with these vehicles as I have my Duramax to handle that.

 

Either engine, with bigger fuel injectors (50# form the 8.1 liter) are a drop in..
Bigger fuel pump to supply more fuel
and add a turbo with 10 psi will be reliable, and give you more power than you probably can imagine.

the 4th gen have stronger connecting rods then the gen 3. But anything under 600hp the gen 3 rods are more than sufficient. This has been proven and beaten to death for years now.

A fun weekend ride, is a nice 500 RWHP vehcile that is lots of go, and fun for not too expensive