Omega Doom

iTrader: (2)

a friend of mine told me that LS3 heads and intake would fit on a LS2/6.0 block is that true and if so what are the typical gains RWHP wise?

96capricemgr

iTrader: (1)

The LS6 makes more power per cube than the LS3 with less compression.

The LS3 is 8% more displacement 20%+ more head flow, .2 more compression, very similar cam possibly using the same lobes in different combination(Late LS6 intake early LS6 exhaust) and manages 6% more power and according to ALL testing reduced lowend below say 4000ish rpm even on strokers.

http://www.hotrod.com/how-to/engine/...re-port-heads/
Even compared to 317s with less compression and a rectangle spec cam that 20% more airflow only leads to 7% more peak power again with losses down low and according to Brian Tooley the chamber on your existing 243s is so much better than 317s that when they ported a set of 243s and 317 with the same CNC work, then milled for the compression to be equal the 243s made 20hp more than 317s which would greatly close the gap with the LS3 while retaining the lowend those lose.

Yes that stuff will fit, but as an LS3 owner I would suggest you look beyond flowbench numbers and skip the LS3 stuff.

The 6L80E behind the LS3s has a 4.03 first gear rather than the 3.06 first of the 4L60E, that is used to hide the poor lowend response. An SS or Camaro with LS3 has factory gearing(first) equivalent to a 4L60E with 4.10s behind it.

Omega Doom

iTrader: (2)

thank sir I appreciate that info that is very interesting so does the same apply for the LS2/6.0 engines though

96capricemgr

iTrader: (1)

The LS2 shares heads with the LS6 and has a compression advantage and displacement advantage and has the early LS6 cam BUT the intake is a step backwards, my understanding is it is not as well constructed and there are leaks between intake runners that screwup wave tuning. Some say the tuning is more conservative too.

Omega Doom

iTrader: (2)

yes I understand that the LS2 intake was a big weak link so if it will fit wont the LS3 heads and intake be a huge upgrade?

96capricemgr

iTrader: (1)

If you believe flowbench numbers are THE measure of performance then they are a massive upgrade.
If you believe in only peak numbers and couldn't care less about responsiveness and torque below 4000rpm then again they are something of an upgrade but not that big of one,
and if you value responsiveness and torque at non-WOT rpm levels then no they are not an upgrade.

speedtigger

iTrader: (16)

The combination of the better heads and intake should be a very nice upgrade for you. I would bet you would gain 35 horsepower or so. You will lose a little compression, but I would make the trade myself.

96capricemgr

iTrader: (1)

People quote 35hp but I want to know based on what? The link I posted showed 38hp vs. 317s on a STROKER with the 317s being down on compression and saddled with a rectangle spec cam.
The 243s are recognized as making more power than 317s due to a vastly better chamber so the difference will shrink, and would shrink again with appropriate cam, and would shrink due to more compression from the 243s vs. ls3s.

Magazine tests are imperfect but it is what we have. Also notable is the torque loss below 4000, again this is on a stroker but I am sure smaller displacement and more shrouded 4.0 vs. 4.03 bore will fix that right?

Now the test is with each having a FAST intake, it isn't stock vs. stock but again it is the test we have.

MX6.0

It's gonna be tough to get an apples to apples comparison between the two heads since they both need different cams to make them shine.

But I will say that I've been very pleased with my setup. Untouched LS2 bottom with untouched LS3 heads/intake/injectors and a fairly mild cam.

speedtigger

iTrader: (16)

Wow. That looks like you gained about 35 horsepower.....

MuhThugga

If you mill the LS3 heads .030", that will keep your LS2 compression to around 11:1. The cost to mill is around $80.

I went from a Torquer V2 and 243s making 430/390 to a 227/235 cam and LS3 heads making 470/410. The LS3 heads are a good budget option. You just need to verify piston-to-valve clearance due to the larger intake valve and keep camshaft overlap to a minimum if you plan on doing a lot of street driving.

96capricemgr

iTrader: (1)

I read that to mean the 35hp included the cam, hopefully he will clarify.
Let's not forget the LS2 intake is usually a step backwards from the LS6 due to inconsistencies in the sonic welding.

96capricemgr

iTrader: (1)

Taken from another post by this guy.
https://ls1tech.com/forums/generatio...l#post18513634
Based on that I would say the blue line was not even the LS2 heads...............

MX6.0

You'd be correct. I never said the blue line was with 243 heads. Which is why I stayed that it would be tough to get an apples to apples comparison. I should have specified. The blue line was the exact same setup with 1.5" shorties and 2.5" duals. Red is 1 7/8" LT's with 3" duals, nothing else changed.

When I bought my engine the FAST92 was destroyed in shipping. At that time, LS3 heads were $315/ea and a brand new LS3 intake/injectors take off was $300. So for me is was a no brainer to do this versus buying another FAST intake.

Omega Doom

iTrader: (2)

so damn for about 1k you bought an LS3 heads and intake wih injectors

MX6.0

Yep, and I sold the 243's (which already had dual springs) for $600...
Like I said, it was a no brainer for me.

96capricemgr

iTrader: (1)

and in a 2400lbs car the lowend hit wont be noticed............

Omega Doom

iTrader: (2)

thanks sir I think im going with the same set up as yours here soon only ill add the cam I already have in my LS1 which is a RPM 5 cam 238/244 on a 110 LSA

96capricemgr

iTrader: (1)

and even the LS3 head lovers will tell you they are cam sensitive and overlap sensitive so you want to use a high overlap cathederal port cam?

Sounds like you made up your mind based on flowbench numbers alone and can't be bothered with understanding anything.

Omega Doom

iTrader: (2)

for me it comes down to cost and availabilty