I was wondering what makes the 6.0 HO motor have 345hp? I know that the 6.0L has a bigger stroke and bore than the 5.3L. Does it have a different intake, cam, etc. that tweaks out that extra 60hp than the 5.3?

 

mainly it is the extra displacement. the 6.0 heads flow really well too.

honesly i think that 345 rating is WAY low.

 

Yes, the LQ9 has different cam specs and a higher cr.

 

In a nutshell, the bore is larger, the stroke is the same for the 5.3/5.7/6.0 (3.622") and the compression ratio (CR) is higher due to flat top pistons with no dish (like your 5.3). The LQ9 burns premium gas is set up with more timing advance and the powertrain control module (PCM) is programmed (tuned) differently. If your 5.3 heads were milled (shaved) to raise the CR up from 9.5 to 10.0:1 and the tune were a bit more aggressive you'd see more torque and HP too. Fundamentally, except for bore and CR and some improvement in head flow, your engine and the 6.0 LQ4 or LQ9 have about 85% parts commonality.

Steve

 

Cam specs and heads are the same between the two motors.

 

honesly i think that 345 rating is WAY low.

parish8
What do you think the actual HP is?
Would the LQ9 heads fit on my 5.3 and make a nice improvement?

 

These are the cam specs for the 345hp 6.0 lq9
207/196 479/467 116

and these are the cam specs for the 00+ 5.3 lm7
190/191 466/457 114

The 99-00 lq4 did share the same cam specs of the 00+ 5.3 though.

 

I think the HP rating may be very close, personaly, but the torque figure may be a little low. Of course, I am making these guesses based on driving a 6000lb+ vehicle with this motor in it.

Todd

 

i think the originaly question may have been missed. where does the extra hp of an lq9 come from vs a 5.3

sure the heads a diferent, the cam is diferent, the tune is diferent....but it is the extra cubes that are making the most diference.

as far as the hp goes on the lq9, i dont have an lq9 but i did dyno a stock lq4 and got 285rwhp, another member got 290rwhp. lets just call it 285hp. that 285 hp is thru a heavy power robbing driveline consisting of 4l80e, tcase and big tires. lets call that 20%.

356hp is what it calculates out to after figureing in the 20%. that is for a low compresion lq4, how much more is an lq9?

 

Call me crazy, but i think the extra HP the HO6.0 has over the 5.3 comes from the compression, heads, and cam. The big jump in torque i give to the extra cubes and higher compression.