Just wondering what the difference is btw the two. HP/TQ difference, cam preference? Im in the early stages of putting a combination together but cant find much about this difference....Thanks in advance.

 

In stock form the 6.o heads flow a little better than the 5.3. The 5.3 has a little more compression. With the heads worked over you need to talk to whom is doing the work on the heads. What are your goals out the heads? Is there a budget? How high do you want to rev it? Do you want peak hp or power under the curve? Are you looking for street or strip performance? I ask because there are so many options out there. Most people go with the 243 ls6 heads or the 5.3. I went with a 224/228 581/588 112lsa cam and the 5.3 heads and made 409 rwhp 405 rwtq. There are many choices of heads. AFR, TSP, Patriot, ETP, Dart, Trickflow to name a few.

The hp/tq difference is mainly going to be affect by the cam you choose and your supporting mods such as the intake and headers. You definately need some lt's and tune to get the most out of the heads and cam.

 

I debated between 5.3's vs. LS6 heads, and found that the biggest difference was in compression and the intake runners. The 6.0's are basically the same as the LS6, just without the Ti retainers. Basically, the 5.3's will have more static compression, which you may need if you buy a bigger cam that drops your dynamic compression ratio too far. You can, however, use a Cometic gasket on the 6.0's to lower the SCR, or you can have them milled down, so you don't have to go with the 5.3's to get higher compression; it's just typically a cheaper way of getting it (ie. no milling or high dollar gaskets).

The same cam on 5.3's will have a little bit higher DCR than the same cam on LS6/6.0's. This higher DCR also benefits the low end, which is why I picked the 5.3's. The smaller intake runners on the 5.3s also helps low end, because it increases the velocity of the incoming air. I don't think it's a humongous difference, as is the case of AFR's, which are much lower (look at the difference between the low end on a set of AFR's vs. LS6 with the same cam, and you'll see significantly higher low-end torque).

As far as flow is concerned, my understanding is that LS6/6.0's will flow better than 5.3's at the same level of porting. In other words, Stage 1 6.0's will flow better than Stage 1 5.3's. I went with Stage 2.5 5.3's, which flow better than Stage 1 LS6's.

 

Well Im looking for HP under the curve. Not really concerned with creating a dyno queen. More importantly Im interested in high torque. I have most of my fun from 0-100 and Im not lookin to get the tach much past 5500 as Im pushing 98K miles. Although Im gonna do it right and replace valvetrain with install. So I guess Im lookin at going with the 5.3L? How big of a cam can I match with those heads, if Im correct in assuming those would be t hhe correct choice?

 

5.3 heads have a 61.15cc chamber size, so they raise compression. (desirable for n/a applications)
6.0 heads have 71.06cc chambers which lower compression. (mainly used on blower/turbo applications).

For comparison, LS1 heads are 66.67cc, and LS6 heads are 64.45cc.

 

Don't the 5.3Ls have smaller valves and ports than the LS1 heads in stock form? I know the 6.0L (LQ9) heads are basically LS6 ports with big (71-72cc) chambers.

 

LS1, LS6 % 6.0 heads share the same size valves, 2.00" intake, 1.55" exhaust.

The 5.3 heads have smaller 1.89" intake valve, same 1.55" exhaust valve.

As for port sizes,

LS1& 5.3 - 200cc intake, 70cc exhaust
LS6 & 6.0 - 210cc intake, 75cc exhaust

 

Decisions, decisions.....




Yer makin' my brain hurt.

j/k - Thanks for the very informative post. I really need this to help with my own decision.

Tex_Vette

 

Hey lots of good info, thanks a lot guys!! This is one question that I have definitely punched the search button on a few times and just couldn't seem to find the info I was looking for.

I know for a fact that I will not run forced induction on this car. So I wont be missing out on anything by going with the 5.3's, especially if Im looking to keep my compression up, correct? Again, still curious, how big of a cam can I run on the 5.3's without over stressing them?

 

I don't think you can really over stress the heads. It's more of a stress to the compenents of the heads such as the springs, titanium retainers, etc. I went with crane dual springs. They say once you pick your cam get the next size up. Alot of people regret putting in too small of a cam. I recommend the 224/228 581/588 114 lsa otherwise know as the mamo cam. It produces great power from 2500-6500 rpm and is considered to be on the upper end of a small cam. I have my rev limiter set at 6500. With a good set of heads and the supporting bolt on 400+ rwhp is no problem.

I went with a 112 lsa which a real lopey idle compared to the 114. Good look on your decision.

 

Again, still curious, how big of a cam can I run on the 5.3's without over stressing them?[/QUOTE]

You can run a cam way way way past your desires on the heads with dual springs, titanium retainers, bronze guides. A cam that will rev to 7k rpm. When you go with over .600 lift you need to chech piston to valve clearance. But with your goals you do not have to worry about.

I have the 5.3 stg 2 heads milled .010 and my next project is to super charge it. Who says you can run FI on 5.3 heads.

 

I don't think you'd want a cam that would be too big for those heads... You will run in to piston to valve clearance with those heads and some of the bigger cams, but we're talking some big 'ole nasty, lopey cams in the mid 230's and above (just guessing here).

Like Kendo said, a cam in the 220's range would make plenty of power without killing your low-end. Just make sure to mind your dynamic compression ratio; that single number has the biggest impact on low end. The larger duration and wider the LSA, the lower your DCR will be. You should target around 8.5 or 8.6. Look on LS1tech.com for "Pianoprodigy"s calculator. It will give you your DCR for a given cam and heads.

I have a 224/224 .581/.581 on a 112, and I'm hitting 410 at the wheel with 350 torque from 2,500rpm and on. It's a nice low-end. I'm around 8.5DCR. If you go with the same cam on a 114, the DCR will be lower, and the low-end torque won't be quite as high. If you go with a 224/228 on a 112, the DCR will be a bit lower, and the cam will be a little bit lower in torque down low, but will push a few more hp at the high end. Just research, research, research. Check out LS1tech.com and look for dyno graphs for various combos. You can see mine by searching here under posts started by me to get a feel for what my setup looks like on the dyno. Good luck.

 

FWIW, that's the cam I put in (on the 112 LSA) with the AFR heads and AR Long Tubes. I got 420 rwhp and 400 tq with an A4. It's a tried and true cam that gets very good results.