Stupid Questions.....again.

[68shortwide]

So I'm thinking of buying a 5.3 off someone thats recommended by a friend, its got the heads off so anyone can check the cylinders and pistons, 84k on it, its intake to oil pan and only $500 but i think i could get it for $400. How hard would it be to use the 5.3 and drive on that while i build a 6.0 and then swap the two? What kind of issues would i run into there? I know id need a retune and small stuff but any big issues? And will a 4l80E fit a 5.3? I would think yes but I've heard multiple varying opinions from different people.

[clinebarger]

A 6.0L is a direct fit in place of a 5.3L, The engine tune is not that different between the 2.

A 4L80E will fit a 5.3L, Need a 4L80E flexplate, Spacer, Crank bolts & stock 4L80E converters take 6 bolts vs 3 on a 4L60E.

It will make it easier to have a 4L80E Harness & ECM.

[68shortwide]

Im really considering this, id save a bit on gas while i build the 6.0 long block and then i can just take a weekend or day and swap out and gain a couple hundred hp

[BR3W CITY]

Originally Posted by clinebarger

A 6.0L is a direct fit in place of a 5.3L, The engine tune is not that different between the 2.

This is true, but be careful with this statement. The base truck "v8" tune can run either engine assuming neither was a flex fuel and both are GenIII, but there will be some significant differences if there has been any "tweaking" (or other notwithstanding factors).

To clarify; If you have the VATS and missions stuff removed but the rest left relatively stock, the same tune will have little issue running either motor...or any of the GenIII4.8-6.0 motors for that matter. The computer will use the MAF and 02's to make the minor corrections as needed. However, the "hotter" a truck is tuned, the more specific certain parts of the tune become in regards to timing, fueling, defuel etc. Even moreso when considering things like SD tuning and forced induction.

Were you to build yourself a 6.0 with some bigger heads and deck work, a new valvetrain, cam, trunion and bearing upgrades,and a fueling system to feed it...you may be unhappy with the results on that existing "hot" tune. IMO I'd rather risk running a bone stock tune on a new built motor, than running a performance tune from a different build. Either way, the tune would need to be modified for the current setup regardless of the starting and ending combination.

I hope I didn't just make that as confusing as I fear I may have.