LS6 -vs- LS3
 

I see and read about a lot LS swaps for many vehicles and I see most go for the LS3. The LS6 is an awesome motor and limited to just the Z in factory form whereas the LS3 is in a variety of GM vehicles. The LS3 has what 30 or so more horses than ours. So question is, not to be biased as a Z owner (you the one reading this), which is a better motor in stock form, which has better mod performance, and if you were doing an LS swap in a non Z car what motor would you choose?

School me on the LS3 hype thing - I'm curious to know.

The ls3 has .5L more of displacement, plus much better flowing stock heads, ls3 flows a max of around 330cfm intake vs 270cfm for the ls6. The ls3 has much greater mod potential and can make big power with relatively minor mods. With just a CAI, LT's a cam upgrade and a tune they can put down 500+rwhp. The only downside I've heard to the ls3 is that it can have oiling issues during continued hard cornering in auto-x, while the ls6 doesn't have this issue. The main reason you see ls3 swaps into so many cars these days is due to the fact you really can't buy the crate ls6 anymore. So your ls choices are ls1/2 or 3. For similar costs, which do most people choose? The ls3. The ls6 is still a great engine as well, like they say though there is no replacement for displacement. :D


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The LS6 is an excellent motor especially for its time but the LS3 is a much better motor overall. The LS6 is an old design, it's really a glorified LS1 which first went into production way back in 1997. The LS3 is a solid decade ahead in terms of technology, etc. The LS3 is more cubes but the biggest difference has got to be the heads. The 243 LS6 heads are the best cathedral heads out there but they really can't hold a candle to the potential of the LS3 castings.

IMO, nothing wrong with a good old LS6, plenty of potential for me. But for the person who really wants max potential or a more modern motor the LS3 is an excellent option.

Agree with the others, LS3 is better, and the LS6 was also in the CTS-V 04-05.

Excellent information. I didn't realize the heads were better than the LS6 heads nor did I realize it was .5 larger on displacement.

Thanks

EXCELLENT response!!!
Please DO clarify if the LS3 HEADS can be successfully transplanted onto a LS6, AND if there are any downsides (if any) or do the improvements outdo the limitations:thumbs:

Ls3 heads will not bolt on the Ls6. LS6 blocks can only use LS1, LS6 and LS2 heads. Using heads designed for larger engines will cause valve-to-block interference

I believe small bore ls3 heads are available if I remember correctly

That is true,i was thinking more along the line of stock heads.There are after market LS3 heads that will work on the smaller bore LS motors.Thanks for the correction.

To use LS3 heads, you'll need a 4" bore.
the middle ground between the two blocks would be the LS2, which can use either LS6 or LS3 heads, and sit in the middle displacement wise also.

If you are planning on using a LS6 block to base your build, there's aftermarket heads that are available that allow you to keep the LS6 intake setup. It's pretty easy to H/C an LS6 for 450+rwhp, but if you're starting with a blank slate, start with a LS3. BTW, you can sleeve a LS6 block to beyond 427c.i. if you choose, allowing the use of big bore heads. Depend on goals, and budget to guide your decision.

A good friend has a new LS-3 in his 98 460 HP he likes it runs great I have 04 Z0-6 built a little 505 FWHP + I like it runs great . . I don't think lots different in the two you can get HP parts for both he did get a warranty with the new LS-3 me no. GM will stand behind the new LS-3 motors . You can get a 505 HP one and the price not bad ..

LS3 is the way to go if for no other reason than the 4.00" bore. More cubes, better heads, upgraded reluctor wheel and the many incremental design improvements add up to a better starting point.

The LS6 is no slouch, but I just don't see the upside if starting from scratch.

Some people are swapping because a LS3 525HP crate engine is so dang affordable. I think Jegs gets about 6k for them.

[QUOTE=charger21;1592709038]Some people are swapping because a LS3 525HP crate engine is so dang affordable. I think Jegs gets about 6k for them.[/QUOT The Ls-3 Motors that Jegs sells are built by GM and warrantied by GM 3- years on the LS-3 460 HP I would say the same on the 500+ HP ones , not bad for what you get .. GM has made it easy to change over to the new LS-3 motor they have a box just plug it in and fire it up a friend has one in a 98 easy change over was not that big a deal looks stock runs very good..

I swapped to the LS 376/480 after an untimely valve spring issue ended my LS6's life. Granted, GM now claims that motor makes 495 hp, but there is just no comparison between the two. That LS 3 flat out moves that car! I had to upgrade tires in order to put the power down. I'm sure the LS6 can be modded to make that power, but since they were few and far between, I just went with the GM crate engine. I don't regret it.

i have one of each-ls6 in my '04 Z(31k miles) and the ls3 in my pontiac g8 gxp(15k miles). both stock and performing well still!

I am having a rebuilt LS3 put in my 04z right now. I had a timing chain break on the LS6. Only had 48k miles. The timing chain broke which led to bent valves and one broken. The broken one got smashed into the head several times. Then it put a hole in that piston and then cracked a sleeve all the way down to let about a gallon of water into the oil pan. Overall that LS6 was a girl that put out, and I can't complain I guess.

I got the LS3 long block(no electronics) for 3789 plus 200 for shipping from Michigan to CA. The speed shop owner here in town said that that was the best price he'd ever seen for a rebuilt long block LS3. Excited to get to know the new personality. I'm a little nervous about losing the raw edge that everyone talks about the c5z having due that aggressive cam in the ls6. I'm expecting this motor to be more mild in delivery yet have more power. Hopefully it's not too refined....

^^^Wow haven't heard of many ls6 timing chains letting go with such low miles, that's surprising. Same miles I have on mine now. Sounds like you got a great deal on the LS3 though, good luck with the swap.

The stock ls3 cam is really close to the ls6 oem cam.