LS7 vs LS3-480 or 525

[Michael]

Ok... So I think that I have worked through my curiosity and cool factor of using a Mercedes AMG engine in the SLC, and I',m now fairly re-planted in the idea of sticking with the LS engine format. I do have one more question for you guys though.

What is the main reason to choose an LS7 power plant over an LS3-480 or 525? Obviously the horsepower in stock trim is pretty similar. It's certainly not price...

But it seems to me that the LS7 was designed and built to take the punishment that the additional power and load put on the engine.

Is the LS3 in it's 480 or 525 configurations, also up to the same level of performance "sustainability"? Or might it be prone to failure due to the loads, comparatively speaking?

Have the prices come down at all for the LS7's, or are they still in the 13k range?

New LS3 engines are obviously much less expensive than the LS7's. So what then, justifies the expense of going all in and using an LS7?

Thanks,

Mike

 

[Fran Hall RCR]

LS3 or ls376-480hp imho.

My new street SLC is an LS3 with a G96/01 6 speed non LSD trans or a Graz...

Having had an LS7/Ricardo wit as overkill...fun but overkill..

You will never be able to drive either of these packages at WOT for long enough on the street to kill it.

This time I want to be able to really lay into the throttle pedal and not tip toe it....whilst still breaking the speed limit.

 

[Luke Lonberger]

I would agree.

I think most people jump onto the Ls7 because it has more power, torque, dry sump, and displacement. On a street car either engine will be great. The Ls3 is also a more reliable engine. Ls7's have tremendous cylinder head problems.

We won't even allow our corvette customers to run on the track unless they have fixed the cylinder head issues. We have seen too many dropped valves.

On a race application the stock Ls7 dry sump won't keep up anyway, so it's really not a deciding factor.

On a high HP forced induction car the Ls3 actually has a stronger block. Most of our turbo customers end up building the Ls3 for those applications.

 

[Paul H]

There are 600+hp naturally aspirated LS3 crate engines, for the sake of discussion.

 

[Jack]

For a street car, the LS3/480 is all you really need. You'll have more fun driving the car.
More, and it can become a handfull very fast. Even the 525 is a beast, but can be driven. Recently had a ride in a 600RW HP SL-C, the only word to describe it is OVERKILL or AWSOME! Smiled a bunch though.

 

[Fran Hall RCR]

Paul H.
there are no GM 600HP LS3 Crate engines though, which is what we are focusing on here.. these are OEM

 

[Mesa]

A buddy has a ZO6...and I can tell you it just isnt "fast" IMO. Maybe my expectations are too high coming from superbike type power ratios.
We will see.

 

[Fran Hall RCR]

Rob how often do you ride your racebike on the street at WOT

 

[Paul H]

Fran,

I'm aware GM doesn't offer 600+hp LS crate engines, though there are engine builders that do offer such turn key crate engines.

https://www.texas-speed.com/p-3584-tsp-418-cid-630-hp-ls3-turn-key-package.aspx

Having not driven a street car with a ~ 5#/hp power to weight ratio it's tough to equate one's needs to one's desires when you think, well if a 5:1 ratio is good, 4:1 would be better...

I'd love to have a street car that had the visceral feel of a 125cc shifter kart, that is something I can relate to.

 

[John Milmont]

How about this?
http://www.chevrolet.com/performance/crate-engines/lsx-454.html
or
LSX 454R Crate Engine - Race Engine | Chevrolet

I know... even more overkill...

 

[Luke Lonberger]

You really wouldn't want to put an iron block LS into a SLC.

Check out Mast Motorsports. They are good guys and sponsored one of my race corvettes a few years ago with a 416ci Ls3 that made 740 hp on an engine dyno.

Here is one of their Ls7 crate engines. They also offer them in Ls3.
Mast Motorsports High Performance Powertrain Solutions

 

[Will Campbell]

The LS7s come with more technology than the LS3 series engines: titanium rods, titanium valves, sodium-cooled exhaust valves, a factory dry sump that is great for the street, an iconic displacement number, more sophisticated heads with better flow, and great torque.

Whether those features are important to you, or worth the cost difference is a matter of personal choice.

It's easy to make more than the stock 505 HP in the LS7 with an LS3-based engine, and to do so with less money. It's also true that the LS7s have a reputation for valve problems, so that may be a factor as well.

I think the value engine choice is the LS3-376 with 480 HP. Much less cost than the LS7 for about the same power, but of course lacking some of the technology. And 525 HP is just a cam change away with the LS3 (though an LS7 can make 630 HP with a cam kit...)

With that said, I'm happy with the LS7 I have in my car.

 

[Fran Hall RCR]

The OP question related to the LS376 vs LS7 ...

We all know that our good old fashioned pushrod engine can make massive power and cost a lot more than the OP engine choices..but I still say that the LS376 is a great option for a street car....the price is dirt cheap and its a great stepping stone should you decide more power is really what you want a cam swap is all you need as a first step....

 

[mahlon]

We opted for the ls 376/525 hp with the grazziano. We have plenty of fast track cars and wanted somthing more streetable [it is supposed to be my wifes car] This is a combination Fran recomended and I agree with him. It will be easy enough to make it faster if she desires. With miner tuning my understanding is that 580hp is obtainable, we will see as we are getting closer with the build I am sure when she scares herself it will be mine to enjoy.....................................

 

[Mesa]

Rob how often do you ride your racebike on the street at WOT

I was just commenting about whether a car felt 'fast' when driven by a 500hp engine.

I totally agree with you that one would never get close to riding a top flight sport bike at anywhere near it's potential on the street. Same goes for a car. I imagine most people would be well pleased with 400ish power levels, and for street use that very well could be the reasonable-to-live-with power level (maybe for me too). I am interested as to 'why' with my own position on this point :shrug:

But that does not change my current impression (lack of) of a 'fast' street car.

 

[Fran Hall RCR]

Just asking a question Mr. Mesa.... for my own point of reference...:thumbsup:...Hell my new ride only has three wheels...GSXR1000 engine and it feels slow to me, seriously...I have a couple of superbike spec engines too that have a little more punch so maybe they will feel faster....

Whats lacking is not really speed, its torque ....its the push you back in your seat feeling...4000lb cars have a hard time doing that but 2400lb cars with 500hp certainly don't IMHO.

 

[Jack]

There really is no debate. Build it the way you want it!

 

[Stu Coleman]

Hi Mike

I have the LS376/480hp and Ricardo is my SL-C. I didn’t have to agonise over choosing which engine because the car came built like that.
I can tell you that this engine has PLENTY of power for a street car. I’ve now put 3,000km on the car and it’s almost impossible to exploit its potential on the street!
The Ricardo has a final diff ratio of 3.36:1 which is rather ‘long’ gearing…a real world idea of what that means (ventured to my fav stretch of road which is normally a 2nd and 3rd gear section in my BMW M5) I engage 2nd gear in the SL-C and go WOT with the intention of finally reaching redline… I failed to reach redline as I ran out of road (had to brake for a corner). A look at the data and I was doing 124kmh in 2nd gear at just over 5,000rpm…I had another 1,600rpm to play with!
So, I certainly agree with Fran…I could never kill the engine on the street because it’s nigh impossible to get into and stay in the upper rev ranges for any length of time!

Fran, out of interest, other than overkill, why did you go from the Ricardo to the Porsche transaxle? It seems the Porsche has an even ‘longer’ diff ratio of 3.444:1.
You mention being able to ‘lay into the throttle and not tip toe it’. is that because the LS3 is just more suited to that style of driving compared with the LS7?

cheers
Stuart

 

[Mike]

My two cents: I have the LS376 480hp crate in mine with about 1400 miles and for the money it's a winner. For the street.... it's more than sufficient. If I was road racing and had to hit ungodly speeds I'd need/want more power, but i can tell you that 100mph comes pretty quick in 3rd gear. If you can't put the horsepower to the ground it's mostly bragging rights anyway and if I turn off my traction control you're still able to do all kinds of "hey y'all watch this" death defying stunts.

I previously thought the LS7 dropped valve issue was an urban myth, but a friend just had this happen to his GM crate motor with about 1,700 miles on it. GM put him through the ringer for a bit, but fortunately he's a bit smarter than some of their engineers - they did replace his engine under warranty.

The "stock" LS3 will idle and run like a production car - it will be civil in traffic.
The LS3 (480) has a slight 1st gear buck to it but will still run smooth while under way at 30-60mph and at 1,500rpm!. GM uses a mild cam in their 480hp crate. Get an A/M cam and 500hp and up is in there.
I have no direct personal experience with the LS7 or LS3 525hp crate so I can't offer a drivers opinion.

My prior car was a Lotus Super 7 replica with a GM LS6 (400hp) - 1,475lbs wet and I still think the LS376 (480hp) is a good match in the SLC.

 

[Luke Lonberger]

Another nice affordable option is a stock Ls3. Install a set of valve springs, retainers, pushrods, and a LG G6X3 cam.

We are seeing 502 whp on a 2010 camaro. The SLC will make a bit more since there is less drivetrain loss.

It will also require dyno tuning, but any car like this should with their varying exhaust, intake, and fueling setups.