what's the difference between these head castings? Is there a difference in flow?
On a stock LS1 the LS6 head will increase your CR to 10.5. the 5.3 will increase it to 10.7 which is still very streetable and for a NA engine is just fine. With bigger CR comes a few extra hidden horses, you may need to run premium fuel for now on though.
you are comparing stage 1 heads to stage 2.5 heads though so of coarse the 2.5 stage 5.3 will probably show better flow numbers.
I am not sure about which head flows more air overall. I do know the 2.5 5.3 heads have have bigger than stock valves I think the stage one Ls6 heads are stock valve size.
some people swear by the ls6 heads and others swear by the 5.3. They both are going to make power though. you can always call Texas Speed and see if you can get more details on the differences in heads.
I also think the ls6 1.0 heads allow lift up to .600 with the springs they come with but you can upgrade to duel springs for .650 lift
the 2.5. 5.3s already come with the duel springs I belive but dont quote me on it.
its really about where you want to make your HP.
Performance wise I think the 5.3 state 2.5 will make more hp than the ls6 stage 1.0 however comparing stage 2.5 ls6 to 2.5 5.3 I am not sure.
The Stage 2.5 5.3's will perform better, in almost every application, then the Stage 1 LS6's. But if you can fit the extra couple hundred bucks into your budget, the Stage 2.5 LS6's will outperform the 5.3's 99% of the time! Have you already decided on or purchased a camshaft? What are your goals for this combo?
__________________
Largest Stocking Distributor of LS-x Engines / Largest LS-x Comp Cams Distributor in the Country!
COMP - FAST - PACESETTER - DIAMOND RACING - CALLIES - COMETIC GASKETS - MONSTER CLUTCHES - MOSER ENGINEERING - KOOKS HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK - POWERBOND - ASP - AND MORE!
I haven't seen any difference between the two heads. A friend of mine had 5.3 stg 2.5 heads in his cam only C5 and was going 115mph and I had stg 1 LS6 heads and was going 116mph in my cam only C5. On paper there might be a flow difference but at the track there was not much of any difference.
Keep in mind you are comparing different heads on different cars entirely! Apples to apples, on paper, at the track, on the engine dyno, etc there is definitely a difference!
__________________
Largest Stocking Distributor of LS-x Engines / Largest LS-x Comp Cams Distributor in the Country!
COMP - FAST - PACESETTER - DIAMOND RACING - CALLIES - COMETIC GASKETS - MONSTER CLUTCHES - MOSER ENGINEERING - KOOKS HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK - POWERBOND - ASP - AND MORE!
The Stage 2.5 5.3's will perform better, in almost every application, then the Stage 1 LS6's. But if you can fit the extra couple hundred bucks into your budget, the Stage 2.5 LS6's will outperform the 5.3's 99% of the time! Have you already decided on or purchased a camshaft? What are your goals for this combo?
My goal is to be @ 425rwhp with H/C. The car has LT's and a Honker CAI. It's an M6 and not a DD. I started just looking at the stock LS6 heads but for a little more money I would step up to the cnc'd heads to get the hp.
My goal is to be @ 425rwhp with H/C. The car has LT's and a Honker CAI. It's an M6 and not a DD. I started just looking at the stock LS6 heads but for a little more money I would step up to the cnc'd heads to get the hp.
What do you suggest Matt?
Either set of heads (5.3 stg 2.5s or stg 1 LS6s) will put you at 425 easily. The 5.3s will get you more low/mid range grunt and the LS6s will be more peakier
The 5.3s will get you more low/mid range grunt and the LS6s will be more peakier
That's not the case! We can mill the LS6 heads a few thou to get the extra compression like the 5.3's (for no extra charge mind you). The LS6's offer better power from idle to redline over the 5.3's on an apples to apples combo. We've tested this on the engine and chassis dyno to confirm this. That's not theory, it's a fact
__________________
Largest Stocking Distributor of LS-x Engines / Largest LS-x Comp Cams Distributor in the Country!
COMP - FAST - PACESETTER - DIAMOND RACING - CALLIES - COMETIC GASKETS - MONSTER CLUTCHES - MOSER ENGINEERING - KOOKS HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK - POWERBOND - ASP - AND MORE!
That's not the case! We can mill the LS6 heads a few thou to get the extra compression like the 5.3's (for no extra charge mind you). The LS6's offer better power from idle to redline over the 5.3's on an apples to apples combo. We've tested this on the engine and chassis dyno to confirm this. That's not theory, it's a fact
Matt, looking at your website you have so many cam options with the LS6 H/C kits. How would I know the specs of all the different grinds?
Would I be better off contacting Comp Cams on their recommendation?
They are just down the road from me
There is the majority of our shelf-stocking cam grinds. We have numerous others we offer and grind frequently, and can of course custom grind them as well
__________________
Largest Stocking Distributor of LS-x Engines / Largest LS-x Comp Cams Distributor in the Country!
COMP - FAST - PACESETTER - DIAMOND RACING - CALLIES - COMETIC GASKETS - MONSTER CLUTCHES - MOSER ENGINEERING - KOOKS HEADERS - ARP - GM BOLTS AND GASKETS - MSD - NGK - POWERBOND - ASP - AND MORE!
That's not the case! We can mill the LS6 heads a few thou to get the extra compression like the 5.3's (for no extra charge mind you). The LS6's offer better power from idle to redline over the 5.3's on an apples to apples combo. We've tested this on the engine and chassis dyno to confirm this. That's not theory, it's a fact
So which set of those heads are better for the ms3 im installing?
__________________
2004 GTO IBM M6
K&N c.a.i, Pacesetter LT'S w/custom 3 inch exhaust and x pipe w/ spintech super pro streets, Tb bypass,
20% tint fronts 5% on rears
"SIC GTO" Plate
MS3 coming soon!!!!
i just got some slightly used 2.5 243's they look great.
only thing i dont know about so far is a cam too. im for sure liking the 226/230 sound and around the .600 lift. i read somewhere about the 2.5's liking .625 lift. so im wondering if i should get a custom cam with that much lift.
im in the same boat, only i have the heads. im looking for 430 to the ground, na of course.
The prc 215 are better than all the above right but how many horses do u gain over the 2.5 ls6 with say a ms3 or 4? Also with the ms4 no flycuting will be required correct.
Last edited by HitmanLS1; 11-04-2009 at 09:40 PM..
2.5 LS6's if it's in the budget...Stage 2.5 5.3's over the Stage 1 LS6's if not.
We can setup the Stage 2.5 LS6 heads to clear without having to flycut, like we do on the Stage 2.5 5.3's, for the MS3!
Ok cool ya I want the stage 2.5 LS6's I'll def wait and save my money for those!
__________________
2004 GTO IBM M6
K&N c.a.i, Pacesetter LT'S w/custom 3 inch exhaust and x pipe w/ spintech super pro streets, Tb bypass,
20% tint fronts 5% on rears
"SIC GTO" Plate
MS3 coming soon!!!!
I haven't seen any difference between the two heads. A friend of mine had 5.3 stg 2.5 heads in his cam only C5 and was going 115mph and I had stg 1 LS6 heads and was going 116mph in my cam only C5. On paper there might be a flow difference but at the track there was not much of any difference.
If you don't mind can you tell us the specs on the cams in both cars? I have the stage 2.5 5.3 heads milled to give me an 11.0 compression ratio with a 224/230 cam. My car trapped 116 in 90 degree weather untuned with the stock LS1 intake.
PRC Stage 1.0 LS6 verse PRC 220cc 5.3L Stage 2.5 
