Thread: GP LS4 vs. other LS4's

I just bought my 07 GXP back in Dec., and my dad just bought an 07 Silverado recently with the 5.3. The GP 5.3 is rated at 303 HP right? The ones in the trucks are rated at 310-315 i think. The GP is all aluminum isn't it? I know there are 2 other versions of the 5.3, an all cast iron, and cast iron block with aluminum heads. What does the truck have? My manual says 91+ octane is recommended but 87 can be used with a slight decrease in acceleration. The silverado just says to use at least 87, or maybe it was 85 I don't remember. I would think that recommending 91 would mean higher compression, and in turn mean more horse power. this apparently isn't the case though. Does the GP have more restrictive exhaust or intake? Is the exhaust restricted due to being a transverse mount with the exhaust wrapping around and under the engine? Anyone know the answer to any of this? Is my info correct? thanks

LS4 is a special version.

trucks recieved the vortec 5300.

Compression makes the octane requirements different.

Exhaust isn't that restrictive.

Headers don't add much.

I assumed it was higher compression for the recommending of the higher octane, but I would also assume that higher compression would mean more horsepower not less. What gives it more compression? What is the difference in these engines? I thought they were pretty similar. Is the truck engine not an LS4?

i have a 5.3 sierra and they are way detuned from the factory to run the 87 octane, i put a 93 octane tune in my truck and gained almost 10* of timing. the L33 5.3 is the most desirable because of the all aluminum block and heads and the 325hp. your LS4 comes with 6* of KR and 200* IAT temps because of that big V8 stuffed under the hood with no way for the heat to escapse