285hp, 295hp, 310hp, and even 302hp ???

Dux-n-Dawgs · November 12, 2006

Hey Guys !

I'm new to the '99-'07Classic Silverado and am currently trying to find out all that I can about the 5.3L engine.

I know my '03 has the 285hp 5.3L and that the 310hp is the all Aluminum HO.

But what is the difference in my LM7 5.3L and the 295hp 5.3L to get that extra 10 horses???

What about the 302hp 5.3L that's in the Trailblazer ???

Wasn't it in '04 or '05 they bumped it to 295??? And wasn't it in '06 and '07 Classic Silverado's that got Electric Fans???

Just trying to figure out where the extra 10ponies are coming from

Also, I noticed my wife's Government Truck ('06 Silvy, 4x4, reg cab, short bed, w 4.3L) has a really deep rumbling FACTORY exhaust ........ I honestly thought it was a V-8 under the hood and aftermarket exhaust ................ could this be where the hp increase is on the 5.3L as well????

I've always said "A Wing, A Fart Muffler, and Wheels don't make it a Hot Rod" .... but dang if that little 4.3L don't sound like it's got teeth

Thanks for any and all input !

-Dux

Valsport · November 12, 2006

to my knowledge those small fluctuations between different RPO power ratings is just pcm tuning

ZZ327 · November 12, 2006

one of those 5.3s is a flex fuel engine. they might be rating the extra HP off that.

redvett · November 12, 2006

From 99 to 06 the trucks got different heads, exhaust systems ,cam, & tuning to get better fuel economy, emissions & HP & TQ.

psu05 · November 12, 2006

05 also has the electic fans

Clavin78 · November 14, 2006

Also, I noticed my wife's Government Truck ('06 Silvy, 4x4, reg cab, short bed, w 4.3L) has a really deep rumbling FACTORY exhaust ........ I honestly thought it was a V-8 under the hood and aftermarket exhaust ................ could this be where the hp increase is on the 5.3L as well????

<{POST_SNAPBACK}>

Hell yeah, I have the 4.3L and it sounds like a beast. I love it. I would have never expected that deep of a sound either.

I did not know they made 4X4 with 4.3L.

Dux-n-Dawgs · November 14, 2006

It surprised me too. With the exhaust sounding like it did, I figured Uncle Sam probably bought one with a 4.8L, maybe a 5.3L but I doughted it. She said V-6 and I said 'pop the hood' ................. sure enough 6 plug wires and a sticker on the radiator shroud that read 4.3L ................ it shocked me.

I know the Fed's at my office (neighboring county) have a '99-'01 Chevy that's reg cab, short bed, 4x4 with the 4.3L and it doesn't sound near as mean. It sounds just like the old 4.3 in S-10's and older body style full size Chevy trucks.

I'm still wondering about the hp differences on the 5.3L though .............. everybody I ask has a different opinion other than the new the 5.3L the stronger it is and the better the fuel mileage they got ............ thus I'm thinking Programming more than anything.

OFF-RD · November 14, 2006

Mine is the L33 engine. 5.3L, aluminum block. 310 HP. I thought only the aluminum block engines were rated over 300 horses. My factory exhaust sounds good too...when I got the truck I noticed it sounded good, wasn't nearly loud enough, but it had that good low rumble to it.

The problem with these trucks, I've learned, is "torque management" built into the computer. You don't get to experience the 310 horsepower at all...ever....because they've got the dam*ed computer programmed to cut the power.

Dux-n-Dawgs · November 16, 2006

I agree Off-RD ! I too thought the HO was the only +300Horse 5.3L engine. But when I picked up and flipped through the Trailblazer brochure at the dealership the other day, I seen a 5.3L @302hp as a option. I wished I would have looked a little more closely to see if it was a 'SS' or 'EXT' type option.

Either way, 285 Ponies is plenty for what I need to do. And the gas mileage is KILLER in this truck ! But I was hoping there might be a easy upgrade and get a few more horses from what's already under the hood.

TC2000 · November 19, 2006

The 5.3 H.O. L33 engine uses a higher lift cam and has a higher compression ratio than the 5.3 flex fuel and cast block engine do . Mine also came with electric fans which free's up some power also. Get a Custom tune or Diablo Predator and turn off some of that torque management and you'll be supprised at how much more power you will have