If you're starting from scratch it's a no brainer to go with the LS3.

The ONLY benefit I've ever heard as far as driving goes, was someone (can't remember who, but it was on CF) said they felt like their H/C/I LS6 had a bit more racy feel to the way it made power than their LS3.

Can't confirm that myself, but I did read it here. It even could have just been a better build/tune with their LS6, and I believe it was in the thread about making 500whp out of a stock cube LS6. I'll try to find the post.

 

Who told you that ;do the LS3 and dont look back.

 

[QUOTE=radar502;1592711012]UPDATE : GM has stopped warranting there new crate LS-3 and clam they never did that in the first place WRONG I got the add. were I helped buddy buy one that's he is running right now in his 97 and it says 3-year warrantied motor ???? anyway still a good motor .. I bud has one with around 850-900 HP WOW . Try that with a LS-6 no thanks .. Love my LS-6 with 500 HP..works for me ..

 

My Motor - Ls3 480 (actually 495)

LS376/480 TECH SPECS
Engine Type: LS-Series Gen IV Small-Block V-8
Displacement: 376ci (6.2L)
Bore x Stroke: 4.065'' x 3.622'' (103.25 x 92mm)
Block: Cast-aluminum with six-bolt, cross-bolted main caps
Crankshaft: Nodular iron
Connecting Rods: Powdered metal
Pistons: Hypereutectic aluminum
Camshaft Type: Hydraulic roller
Valve Lift: .525'' intake / .525'' exhaust
Camshaft Duration (@.050 in.): 219° intake / 228° exhaust
Cylinder Heads: Aluminum L92-style port; ''as cast'' with 68cc chambers
Valve Size: 2.165'' intake / 1.590'' exhaust
Compression Ratio: 10.7:1
Rocker Arms: Investment-cast, roller trunnion
Rocker Arm Ratio: 1.7:1
Recommended Fuel: Premium pump (92 octane)
Maximum Recommended rpm: 6600
Reluctor Wheel: 58X
Balanced: Internal

LS6

LS6:
Displacement = 5.7 L. / 346 CID
Bore x Stroke = 99mm x 92mm / 3.90" x 3.62"
Compression Ratio = 10.5:1
Horsepower = 385/405 HP @ 6,000 RPM
Torque = 385/400 #-Ft. @ 4,800 RPM
RedLine = 6,500 RPM
Fuel Cut OFF = 6,600 RPM

I went through two LS/6 short blocks before I said screw it and went with the LS3. I should of done it the first time.

Full warranty is only offered if GM installs it - if a private party installs it - engine still has a warranty but its reduced.

 

Did the original Z06 ECU work with the new engine? There is a 2004 Z06 with a blown engine for sale near me for a good price.

 

The ECU has to be updated. NicD tuned mine -

Im sitting at 425 RWHP and 408lbs ft trq.

Granted if you do a LS3 swap into the LS6 car - you will need some parts. Adapters, Silver Blade TB etc ....

 

LS2 is a damn good engine. It is underrated and is actually closer to 410 to 415 hp at the flywheel in stock form. GM underrated it to not decrease sales on the C5 Z06 and they did not use the same SAE rating as the LS3. There is only a 2 mph trap speed difference between the LS2 and LS3. The LS3 weighs 38 more pounds than the LS2. The LS2 also has a higher compression ratio than the LS3 and it has higher rpm and a broader torque curve making it more fun as a daily. The LS2 was the last LS engine to have cathedral port heads and they are the best for building a modded engine.

 

Sweet copy paste

 

I do what I want

 

So it sounds like the LS3 is still a better motor then.

 

FYI, a version of the LS6 also went into the 2004-2005 Cadillac CTS-V.

http://www.cadillacfaq.com/faq/answers/diff.html

 

why do you say that?... don't get me wrong I love the ls3 but a boosted ls6 is capable of similar power levels

 

Ls6 heads work pretty well. Possible to see over 500whp with a healthy cam in a more radical setup.
The ls3 heads flow better but probably not worth the hassle with all the changes necessary if you already have an ls6.

Mast makes a small bore square port head that will fit the ls6 and make great power with a proven porter.

Also consider with the ls3 style head you will have to go with a fast if plastic is your preference vs. an MSD that can be used for the cathedral head.
Then again an expert, like Brian Tooley, will likely be ably to convince you that a cathedral head is all you need.

 

Lot of factors go into building a LS motor . The limiting factor in my 04 LS-6 is the rod bolts but if you replace them with APR easy 7000 RPM no problem right now red lined at 6800 500 FWHP .. The LS-3 right out of the box has heavy duty parts and will hold up better that the older stock bottom end for the older LS-6 . Heck I helped a friend build a LS-1 with 650 HP and it ran 22,000 miles before it blew a head gasket so you can build any of them with the right parts ..

 

yeah if you want to rev to 7k+ then rod bolts are a good idea but it can handle 6800... I agree that the ls3 is stronger out of the box but if you already have an ls6 it may not be worth all the added cost for a little more strength, especially if you are tearing into the motor or building one from the ground up because a built ls6 will be about the same strength wise as a built ls3... I had tossed around the idea of building an ls3 for my car if the ls6 popped but after thinking about it logically I scrapped the idea because for the amount of power I would want to make I could pick up another ls1/6 or even an aluminum 5.3 block and reuse everything on the top end

 

[QUOTE=neutron82;1595772655]yeah if you want to rev to 7k+ then rod bolts are a good idea but it can handle 6800... I agree that the ls3 is stronger out of the box but if you already have an ls6 it may not be worth all the added cost for a little more strength, especially if you are tearing into the motor or building one from the ground up because a built ls6 will be about the same strength wise as a built ls3... I had tossed around the idea of building an ls3 for my car if the ls6 popped but after thinking about it logically I scrapped the idea because for the amount of power I would want to make I could pick up another ls1/6 or even an aluminum 5.3 block and reuse everything on the top end[

Is true if building one from ground a LS-6 block will work just fine .. The Old LS-1 I helped a bud build a few years back with 650 Hp had a stock bottom end ,it lasted 22,000 miles and just blew a head gasket ,we might could have fixed it and keep going but he was ready for something newer . I helped him install a new LS-3 new GM motor with 500 Hp runs great .. The old LS-1 was a 97 ..