Heads
03-05-2013, 05:23 PM
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Heads
Long time lurker. First off I want to thank everyone for great advice, builds and screw ups so I can learn from your mistakes.
That being said I have a 99 5.3 with a cai, deleted cats into a single 3 inch into a magnaflow. The custom tune was done by PCM for Less for 93.
I just ordered a 2001 ls6 cam and yellow springs. I also just picked up a set of heads from a 2002 5.3 with 65,000 miles on them. Now my question is if I were to do anything to them what would I do? Now I am doing this on a budget and this is my daily driver. I have to set a limit because as most of you know, it never ends. I have no plans of a stall or gears. Again this is my daily driver. The only reason I asked about the heads is because I am having them cleaned at a performance shop. Should I swap the rockers or have it milled for better compression or are the gains limited and leave it alone? Ok advise away
Thank you
That being said I have a 99 5.3 with a cai, deleted cats into a single 3 inch into a magnaflow. The custom tune was done by PCM for Less for 93.
I just ordered a 2001 ls6 cam and yellow springs. I also just picked up a set of heads from a 2002 5.3 with 65,000 miles on them. Now my question is if I were to do anything to them what would I do? Now I am doing this on a budget and this is my daily driver. I have to set a limit because as most of you know, it never ends. I have no plans of a stall or gears. Again this is my daily driver. The only reason I asked about the heads is because I am having them cleaned at a performance shop. Should I swap the rockers or have it milled for better compression or are the gains limited and leave it alone? Ok advise away
Thank you
03-05-2013, 05:43 PM
#2
Staging Lane
This is all just my opinion but I would leave the heads be. Chances aware you won't see a big gain from compression. Not $100 bucks worth anyways. Then you have to retune and blah blah blah. I'm upgrading my rocker arms. I'm just going to use a roller setup because I don't want the engine to make any noise. Performance is after noise for me. Maybe look into a new intake? I see that's common as well as long tube headers. If all else fail there is always forced induction haha.
I have to ask though why did you get 2002 heads? Is there a difference between them I don't know about?
I have to ask though why did you get 2002 heads? Is there a difference between them I don't know about?
03-05-2013, 06:16 PM
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This is all just my opinion but I would leave the heads be. Chances aware you won't see a big gain from compression. Not $100 bucks worth anyways. Then you have to retune and blah blah blah. I'm upgrading my rocker arms. I'm just going to use a roller setup because I don't want the engine to make any noise. Performance is after noise for me. Maybe look into a new intake? I see that's common as well as long tube headers. If all else fail there is always forced induction haha.
I have to ask though why did you get 2002 heads? Is there a difference between them I don't know about?
I have to ask though why did you get 2002 heads? Is there a difference between them I don't know about?
Also one more question regarding the heads. The 02 motor had more hp then the 99. Was this because of the heads? Not my reason to use them but a bonus if true
03-05-2013, 07:35 PM
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Okay consulting my big book of fun the LM7 released in 1999 is said to produce 295hp, the L59 released in 2002 is 295HP as well but it is a flex fuel engine. The LM4 released in 2003 is good for 300HP; that is a aluminum block. The only gen3 5.3 that made more power was the L33 released in 2005 and that has a compression ratio of 9.9:1. That engine made 310HP. All other engines were 9.5:1. It got to 9.9:1 by using the flat top pistons used in the 4.8. Of course these are stock numbers but I think any gains would be in the area of error if there are any.
It really depends on what you want out of the engine. Raising the compression ratio is better. You are already using 93 octane so you could go up into the 10s. That might net more for you. In theory also you get more MPG because you are getting more energy out of the fuel as well. If you got the money to drop why not?
It really depends on what you want out of the engine. Raising the compression ratio is better. You are already using 93 octane so you could go up into the 10s. That might net more for you. In theory also you get more MPG because you are getting more energy out of the fuel as well. If you got the money to drop why not?
03-05-2013, 07:53 PM
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Ok I like the idea of milling the heads. What is anyones thoughts on better rockers or stay with stock? I am getting into a new world so I only know what I read and I know everything on the internet is true and all...
I thought the lm7 99 was 270 and the lm7 02 was 285. I am curious why and is it because of the head design and will this net me gains. Again not my reason to change just trying to find out. BTW the heads I bought were from a 02 Sierra
Below is what I found out on the "internet"
And thanks to everyone who is chiming in. This is what I want, ideas
"The 1999 LM7 engine produced 270 hp (201 kW) and 315 lb·ft (427 N·m), 2000-2003 engines made 285 hp (213 kW) and 325 lb·ft (441 N·m)."
I thought the lm7 99 was 270 and the lm7 02 was 285. I am curious why and is it because of the head design and will this net me gains. Again not my reason to change just trying to find out. BTW the heads I bought were from a 02 Sierra
Below is what I found out on the "internet"
And thanks to everyone who is chiming in. This is what I want, ideas
"The 1999 LM7 engine produced 270 hp (201 kW) and 315 lb·ft (427 N·m), 2000-2003 engines made 285 hp (213 kW) and 325 lb·ft (441 N·m)."
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03-05-2013, 08:18 PM
#8
I thought the power difference was due to the cam... but I guess I have nothing to really base my claim off haha.
If I were you I would sell the newer 5.3 heads. Pick up some 799 castings (NNBS 5.3 heads) that are the same exact casting as the 243's used on the LS6 and LS2. The newer 5.3 have flat top postons so to match their compression you will need to mill the 799's slightly. That would be the best option for power on a budget in my opinion. They out flow the 5.3 heads you have my a really wide margin, and clearly something about it works on a 5.3... GM took that route along with the TBSS larger intake. The newer engines are rated at what, 335? The LS6 cam will offer you much more power than whats in those too. I would think its reasonable to claim an easy 360+ hp (crank HP) out of that combo.
I know you said no stall, but the Circle D restalled trailblazer converter would really make this package come together. It would feel like a totally different ride while still keeping daily driving pleasant and your ability to tow. The converter will wake up the bottom making this truck a beast off the line while all the mods wake up the rest of your rev range. It's also really cheap. Hello 13 second 1/4 mile pass with great stock driving manners.
If I were you I would sell the newer 5.3 heads. Pick up some 799 castings (NNBS 5.3 heads) that are the same exact casting as the 243's used on the LS6 and LS2. The newer 5.3 have flat top postons so to match their compression you will need to mill the 799's slightly. That would be the best option for power on a budget in my opinion. They out flow the 5.3 heads you have my a really wide margin, and clearly something about it works on a 5.3... GM took that route along with the TBSS larger intake. The newer engines are rated at what, 335? The LS6 cam will offer you much more power than whats in those too. I would think its reasonable to claim an easy 360+ hp (crank HP) out of that combo.
I know you said no stall, but the Circle D restalled trailblazer converter would really make this package come together. It would feel like a totally different ride while still keeping daily driving pleasant and your ability to tow. The converter will wake up the bottom making this truck a beast off the line while all the mods wake up the rest of your rev range. It's also really cheap. Hello 13 second 1/4 mile pass with great stock driving manners.
03-05-2013, 08:48 PM
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I have read about the nnbs heads however I wasn’t even going to do the heads however I found a busted exhaust manifold bolt inside and with the new cam and springs opted to find a set of heads. Picked up the set for $125 with under 70k. Not too bad I don’t think. So here I am.
I am not totally dead on the idea of a stall I just don’t think it’s in the cards this upgrade time. I’m just focusing on the cam, lt headers and new to the plan, heads. Give you guys enough time we will be talking blowers.
My goal has never been to have a track truck, I just like to be able to pull people, especially the little (insert high school car dejour here)
I will look into the stall maybe for the summer especially since it is dd friendly. As for now in PA the less I am laying on the ground in the cold the happier I am.
So sticking with the heads I have, I am going to mill, what rocker set up should I do if any matched with this cam?
You guys are awesome... as long as my budget can afford it.
I am not totally dead on the idea of a stall I just don’t think it’s in the cards this upgrade time. I’m just focusing on the cam, lt headers and new to the plan, heads. Give you guys enough time we will be talking blowers.
My goal has never been to have a track truck, I just like to be able to pull people, especially the little (insert high school car dejour here)
I will look into the stall maybe for the summer especially since it is dd friendly. As for now in PA the less I am laying on the ground in the cold the happier I am.
So sticking with the heads I have, I am going to mill, what rocker set up should I do if any matched with this cam?
You guys are awesome... as long as my budget can afford it.