musclecarsrock68

I am building a lq4 for my 95 z71.
I have a block bored over .020 with new flat top pistons and ls2 rods. i have a set of stock ls3 heads milled down .015 and a ls3 truck intake i was planning on putting on it along with the custom pat g cam i just got in the mail, but i also have a set of stock 799 heads i could mill and a fast 92 intake i could put on it. along with a newly specd cam. Just looking to make the most power Opinions?

I have read alot of threads and it seems like for every person that says ls3 there is one that says ls6.

KCS

iTrader: (20)

I'd prefer the 799 castings personally. You're starting off with a much smaller chamber so higher compression ratio is a big advantage right off the bat.

427 zeo6

What are you using the truck for? For real pick-up truck duties I would go with the LS6 heads if your building a modern equivalent of "The Farm Truck" and want fast 1/4 mile times the LS3 heads but, won't have the bottom end of the LS6 heads.

musclecarsrock68

I might pull a SMALL trailer few and far between, a little pop up that a mini van normally pulls for the most part im just wanting it to run 1/4 mile as fast as it can and still be street drivable.

so the higher comp ratio is the main reason you would go for the ls6 heads?

musclecarsrock68

ok score so far
799-1
ls3-1

armyboyatc

iTrader: (29)

I'd do the LS3 heads. They flow ridiculous. They won't have the bottom end of the LS6 heads but they will pull like hell up top. If you're lookin for trac times then the choice is clear, LS3 all day.

Baconz28

It's hard to say since the engine is going into a truck. If you was building a car I would clearly go with LS3 top end but since it's a truck the 799 heads might be a better option. Your camshaft with either combo is what's go make the difference.

427 zeo6

If you want FAST....Go LS3

If you want TOW....Go LS6

Seems like your leaning towards LS3 heads if all your doing is towing a little "pop up" and wanting to run truck at the drags by all means go LS3 heads, going to a L92 intake will help bottom end power or go with the LS3 intake but, then because of the change in throttle body location all accessory brackets/pulleys and waterpump will need to be changed over to Camaro style bracketry running costs up by quite a bit over just a head swap.

Myself, I tow DURAMAX....Choo...Choo!

musclecarsrock68

i have the l92 intake for the ls3 heads. i was also thinking that a little less low end power may help me get off the line with out spinning so hard

KCS

iTrader: (20)

Not the main reason, but definitely a big reason. I think the 799 ports are better than the LS3 stuff, especially on smaller displacement engines. You may make a little bit more power at higher RPM with the LS3 ports, but the trade off is midrange power and a lot of it.

armyboyatc

iTrader: (29)

This isn't entirely true. You will lose a little low end ill give you that but saying that you'll lose lots of mid range just isn't true. If you have the correct combo such as milled heads, cam, intake and tune then you wouldn't lose hardly anything through the midrange.

People get so wrapped up in this midrange power. If you're building a road race SCCA car then sure, you'll need it. If you're gonna cruise around town and race people from stop light to stop light and go to the 1/4 mile track then a big cam and high stall with big heads that makes peaky high HP numbers will be king. I've never seen a drag race conducted at 3k RPM's throughout a drag race that didnt involve a diesel.

Bottom line is if your parts match up to a good solid combo and you have a good tuner then you might give up a touch of midrange but you'll blow the LS6 setup out of the water on race day period. More air + more fuel = more power.

armyboyatc

iTrader: (29)

This is that typical old school myth crap that's floating around. Let me put it to you like this, GM didn't start putting the square port L92 and LS3 heads on 6.0 motors so they will make less power. The LY6 is a perfect example of this. It's basically an updated Lq4 motor with L92 (square port LS3 style heads) and a different intake. It makes 385 flywheel horse power from the factory on 87. This engine is found in GM's HD line up which is marketed for who??? People who need a beefier truck or van to HAUL AND TOW stuff around. The choice is clear here, GM is moving away from cathedral port stuff for a reason, they have figured out how to make a GOOD COMBO with square port heads that flow more air to produce more power and make a more efficient air pump. This is 2013 almost 2014, I don't know about most here but I like moving forward with technology. 799 heads are old technology and as far as I'm concerned, make a good door stop.

You're more than welcome to come drive my LY6 car with milled heads and a cam and tell me how much it lacks midrange power lol.

KCS

iTrader: (20)

I disagree. Cubic inch for cubic inch, you take a loss with the LS3 heads. If you compare the graphs of a 376ci LS3 to an LS6 head 364ci LQ4, that extra displacement bumps the torque a little bit so that it doesn't look so bad.

However, the LS3 heads on a LQ4 usually show bigger losses in the midrange and often times, mediocre peak numbers. A lot of people here, knowledgeble people, don't recommend using the LS3 heads on a 4" bore because of the shrouding and the weak powerband it often produces. You may get your peaky powerband, but overall power suffers, and the car slows down.

KCS

iTrader: (20)

GM designs these engines around different criteria than most of us enthusiasts want. I think the LS7 was a home run, but the LS3 was not. The shape and size of the ports aren't really appropriate for the smaller engines, like the 6.0L/6.2L engines. It's okay in stock form, with stock manifolds, and stock camshafts, but once you get outside of that with aftermarket cams, etc. again, you see they weaknesses of the big ports.

They are a great budget head for the larger engines that need the larger cross sections, but on smaller displacements, I would still go with the cathedral ports.

armyboyatc

iTrader: (29)

This just isn't true. Proof is in the design. There have been several discussions on this and the LS3 heads are an upgrade over LS6 heads all day. For every dyno graph you can provide showing a weak sub par combo putting down less average power, I can provide one showing a car with a solid combo that has gained total average power. I think you should do a little more research before you display what you're saying. There is no way my motor for example would produce the power it does with smaller heads. I do not lack midrange power at all. My cam is designed to take advantage of the port design and works very well. There are numerous 6.0 cars that have made the change and are very pleased with the results. Just because you can't make them work doesn't mean others can't. Big shops such as Tick Performance, Vengance and Virginia Speed are pushing 6.0 cars out the door with 500 + hp with little to no port work and a relatively small cam. They all agree that it is an upgrade and they know how to make it work. Martin at tick (their camshaft guru) is running square port LSA heads on his motor so I'd like for you to call him and tell him that his car would be faster with a set of 799 heads and report back to us what he said.

You are entitled to your own opinions but not your own facts. Just because you can't make them work doesn't mean others cannot and have not. Stock for stock the L92 head is a better head and disputing that is a little ignorant. It's on paper, it's on the dynos and its at the race track. It's time to move forward with technology instead of being hung up on how things were in the old days.

armyboyatc

iTrader: (29)

OP and KCS please read the following article on the square port design. There is lots of math involved and you can not argue with math. This article shows why the square port is advantage and tells you how it produces torque, and velocity.

http://www.afdracing.com/square%20po...sx%20heads.doc

Do not become a victim of advertisement and mis truths. New texhnology is better, it's how you apply it to your application that makes or breaks a good combo.

armyboyatc

iTrader: (29)

Here is a thread on here about this article. Listen to what the heavy hitter speed shops are saying and not just some shade tree guys. You will see that these new heads work period.

https://ls1tech.com/forums/generatio...ort-heads.html

KCS

iTrader: (20)

Thanks, that was a good read. Not sure how that was supposed to help your argument...

armyboyatc

iTrader: (29)

And I'd like to point out that Pat G also said that from 3k up his Denali "pulled like a raped ape"

Virginia speed is pushing 500hp L92 headed 6.0's regularly.

Brian Tooley admitted in that thread that the L92 heads did make more overall power.

Also, most of the posts you pointed out are 3 years or more older. When this concept was fairly new. You should be fully aware of how much technology can and has changed.

Now if you want to argue idle to 3k then you win but in a drag race, what RPM's are generally used?

armyboyatc

iTrader: (29)

You also didn't put any of the big shops quotes in there that talked about how much they worked. All negative posts telling half the story. Imagine that......