5.3HO? or what

[RBR594]

Im new to LS, so heres my question, How do you tell the difference in a 4.8,5.3,or 5.3HO? i was told a 5.3 has dished pistons but a 4.8 and a 5.3 HO has flat tops. how do you tell if its a HO (High Output)?

[pajeff02]

The iron block 4.8 and 5.3 are identical. Flat top piston is a 4.8 and dished piston is a 5.3. That's my understanding. H.O.? Not a clue.

[SMWS6TA]

True but if advertised as a 5.3 he may have some bargaining room for misrepresentation of product purchased.



You can convert it to a 5.3 by changing the pistons. DSS has some very affordable forged pistons.

[RBR594]

True but if advertised as a 5.3 he may have some bargaining room for misrepresentation of product purchased.



You can convert it to a 5.3 by changing the pistons. DSS has some very affordable forged pistons.

What’s DDS ?

[SMWS6TA]

D.S.S. Racing Pistons - High Quality Forged Pistons For The Racing World

[SMWS6TA]

You also need to know if this engine has Active Fuel Management.

[tug686spd]

From memory here, iron block 4.8 does have flat tops but with a shorter stroke and longer rods than every other Ls. So you can't just change pistons to get a 5.3. Iron 5.3 does have dished pistons with the standard 3.622 stroke crank. The compression height and bore diameter on the 4.8 and 5.3 pistons are the same so you can put flat top 4.8 pistons in a 5.3 to bump compression. There is H.O. 5.3's but pretty sure they are all aluminum blocks. They also have flat top pistons and 243/799 heads. 4.8 stroke is 3.26? I believe.

[SMWS6TA]

From memory here, iron block 4.8 does have flat tops but with a shorter stroke and longer rods than every other Ls. So you can't just change pistons to get a 5.3. Iron 5.3 does have dished pistons with the standard 3.622 stroke crank. The compression height and bore diameter on the 4.8 and 5.3 pistons are the same so you can put flat top 4.8 pistons in a 5.3 to bump compression. There is H.O. 5.3's but pretty sure they are all aluminum blocks. They also have flat top pistons and 243/799 heads. 4.8 stroke is 3.26? I believe.

Correct, it's 3.267" I had forgotten about their cranks.

Interesting tid bit - I've been reading a lot lately of boost guys using the 4.8 cranks with large bore pistons and having custom cams to spin up into the 9,000 rpm range for their turbos and superchargers. De-stroking is what I read. Supposedly the boost builds higher as the rpms go up.

[SMWS6TA]

Here's an article that should help.


4.8L VS 5.3L Engine - Tech - Little LS Slugfest - Super Chevy Magazine

[tug686spd]

Destroking has been around a long time. Remember the chevy DZ302? As far as the turbo rpm thing goes short stroke is always best for rpm'. There is less side loading on the pistons and bores with the correct rod ratio. With the 4.8 and 5.3 the rpm range is extended out further because of the smaller cubes even with your standard aftermarket 5.7-6.0 cam. Add boost and it extends even more as the engine doesn't have to work to pull in its air. The biggest advantage to more rpm in boost is power management. I'm sure everyone's heard you can't bring nitrous on to early because of possible backfire but mostly because to much power on a rotating assembly turning to slow. So it bends rods, holds heat in longer, kills pistons and a bunch of other bad stuff. Same with turbo, try to buch boost to low in rpm and same prob can happen. So you go with more rpm. Run a little looser converter so you can start higher in the rpms then ramp in more boost as the rpm increases. More rpm's also means more exhaust gasses being processed and that is what turns the turbo. Good example would be most of the fastest stock bottom end 5.3's run 88mm or bigger turbos because it's kind off a win win. The big turbo won't spoil at lower rpms on the small motor so it hard to get enough boost to bend rods down at 3k. And it it makes managing the power easier for launch. But once moving and rpms climb and turbo really start lighting off you can poor on the boost.