JCox23

Stock for Stock, what's the better bang for the buck if you are looking to start modding right away?

A LS3 GS or a LS7 Z06?

Here's what I know currently owning an '08 Z06

Obviously there are a few things that need addressed when modding a LS7. You either need to replace the heads or replace the valve guides. I replaced the vavle guides and also replaced the sodium filled valves with solid stainless steel. this cost about $1,000.

Next is the bottom end. It appears these can't hold much boost at all without rebuilding the bottom end. It seems it's hit or miss on the true limits of the bottom end NA or spraying.

Now cam only my car makes 540rwhp and 505rwtq.
I recently added a nitrous kit with stand alone fuel system to ensure more safety while spraying. On a very safe tune my car made 664rwhp with a 150 shot. This was all the more myself and my tuner wanted to push the boundaries of the stock bottom end LS7. Obviously that's only a 124rwhp gain on what should otherwise be a 150rwhp gain which brings me to my next point.

I have heard time and time again from several people, tuners included, that if this were any other LS engine they would feel better putting more to it. Whether it be boost, spray or NA.

Now on the LS3, obviously it doesn't make as much power stock for stock and gains won't be as much cam only. But isn't the over all potential to make bigger power more reliably on the stock bottom end better?

I feel like I have maxed out my power to where I feel is safe on my stock bottom end LS7 and to make more power I need to build my bottom end which undoubtedly will costs thousands. However, with an LS3, I feel like I could throw on a blower, cam and 150 shot and make more power and it will take it.

Now maybe I'm wrong in my thinking but then again that's why I'm making this post. I want to know what you guys' facts and opinions are and if you were starting from scratch and shooting for the goal of say, 700rwhp, just as an example, which car would you choose and why? The Grand Sport LS3 or the Z06 LS7.

Thanks,
Joel

Seadawg

Me personally, If I were going to use it for any kind of racing, for true reliability, and to trust it as a dependable driver, I would not want much over 600 rwhp on either one, with out modifying the bottom end, or replacing it altogether with a 413 setup, purpose built for it.

I would also beef up the entire drive train too. Transmission, rear end, axles, etc.

For street use, and an occasional roll race, many roll the dice with both the LS3 and LS7, there are many out here close to 800 rwhp without full drivetrain mods.

Cor430vette

Well you can see which one GM picked for the ZR1. The LS9 is essentially a LS3 with titanium and forged internals and of course the supercharger, more aggressive cam etc. etc.
The LS7 with its valve train debate....is it the valve guides? The machining which causes the valve seats and valve guides to be non concentric causing the oval pattern? etc etc.
Its not like 505 hp was that much better than 436 out of the box...69 hp big deal. All the extra displacement, titanium and forged race internals on the LS7 are what made it a great deal but after the head fiasco and all the blown engines - all those stronger race internals didnt matter when your car was throwing an exhaust valve...
I had a 2008 base model LS3 with supercharger, headers, meth, tune, fuel mods etc. I was approximately 700 hp at the crank. Never gave me a problem I was going to upgrade the drive train and internals and then I asked myself what for? Who needs this much power....I certainly didnt - so I sold it.
When I came back to the Vette world I wanted a LS7....did a bunch or research on reliability and the LS3 is the clear winner.
This is all just IMOP....of course, and hell what do I know...

LS3:
Engine p/n: 19201992
Balance: Internal
Block part number: 12584727
Block type: Cast aluminum with 6-bolt main caps
Bore x stroke: 4.06 x 3.62 (103.25 x 92mm)
Valve lift intake/exhaust: 0.551/0.522
Valve size intake/exhaust: 2.16 / 1.59
Camshaft duration (@0.050"): 204 deg intake/211
deg exh
Camshaft p/n: 12603844
Camshaft type: Hydraulic roller
Compression ratio: 10.7:1
Connecting rods p/n: 12617570 (powdered metal)
Crankshaft p/n: 12597569 (nodular iron)
Displacement: 376 cid (6.2L)
Maximum rpm: 6600
Piston p/n: 19165089
Piston type: Hypereutectic aluminum
Recommended fuel: 92 octane
Reluctor wheel: 58-tooth
Rocker arm ratio: 1.7:1
Rocker arm intake p/n: 12569167
Rocker arm exhaust p/n: 10214664
Rocker arm type: Investment cast, roller trunnion
Reluctor wheel: 58X
Firing order: 1–8–7–2–6–5–4- 3 (standard LS firing order

LS9 Engine Specifications
Type: Gen IV small block V8
Displacement: 6.2L (376 cid)
Horsepower: 638 hp @ 6500 rpm
Torque: 604 lb-ft @ 3800 rpm
Bore x stroke: 4.065" x 3.62"
Balance: Internal
Compression: 9.1:1
Supercharger boost ratio: 10.5:1
Supercharger: Eaton R2300 four-lobe Roots-style
displacing 2.3L
Block type: Cast aluminum, six-bolt cross-bolted main caps
Main caps: Forged steel
Cylinder head: Cast aluminum, rectangle port
Valve diameter: 2.16" int; 1.59" exh (titanium int &
hollow stem, sodium-filled exh)
Chamber volume: 68cc
Crankshaft: Forged chromoly steel, internally balanced
Connecting rods: Titanium
Pistons: Forged aluminum
Camshaft: Hydraulic roller tappet
Valve lift: 0.562" int; 0.558" exhaust
Camshaft duration @0.050": 211 deg int/230
deg exh
Rocker arm ratio: 1.7:1
Connecting rod length: 6.067
Oil pressure (min w/hot oil): 6 psig @ 1000 rpm
18 psig @ 2000 rpm
24 psig @ 4000 rpm
Recommended oil: 5w30 Mobil 1 or equivalent
(GM4718M spec)
Oil filter: AC Delco p/n UPF48R
Recommended fuel: 92 octane
Max engine speed: 6600 rpm
Spark plugs: GM 12571165 (AC Delco 41-104)
Spark plug gap: 0.040"
Firing order: 1–8–7–2–6–5–4- 3 (standard LS firing order)

C6z06man

LSX block and build to do whatever you want? That's what I would do personally.

old motorhead

I had that decision to make last year. I wanted a new Vette and didn't want a C7. Lots of crazy stuff floating around about the new C7's and teething pains on the new series. It came down to the GS or Z06.

I knew stock power levels weren't going to cut it. 650 to 700rwhp was needed. The Z's weight advantages were enticing. After looking at it from way too many angles, I concluded that the GS was a slightly overweight Z without the "may pop" motor. I ended up buying a new 3lt 2013 GS loaded for $55K.

Currently has a Magnuson Heartbeat TVS2300, mild cam, and bolt ons. Upgraded sways. 660+ rwhp.

I know the Z purists won't like it. I'm pretty happy with it though.

JCox23

I thought I wanted a Z06 for all of those same reasons.. Now I'm seriously thinking of switching to the GS after talking to my friend from ProCharger.

xBoostx

If I had to make the decision I take the bottle off and drive the heck out of that car.

BUT if you "have to have more power" I would spend the money re sleeve the LS7 to 4.185 bore and make a 440 CI N-A making 670 WHP on E85 if available, if not then turbo somewhere under the car, not in front or on top.

I would keep it a ZO6 cause nothing else measures up to it, that's the bad boy.

I love my A6 '11 GS mostly cause is auto but a 427 in front very enticing.

JCox23

See here is my point, you have to keep dumping money into the LS7 in order to make it hold the power of a stock LS3. Trust me I've already looked into the re sleeve option. That's about $7,000 all said and done with a built bottom end. There are LS3 guys making 8-850rwhp on the stock short blocks all day long no issues. I used to think the all mighty 427 was a bad *** engine until I got into one. Sure it pulls hard and responds well to cam only but I could take that $7k and throw it at a stock GS and make more power than a LS7. I'm also looking at getting back into an automatic.

ipmtim

I have an '06Z love the car but.....had the heads rebuilt then still dropped a valve. Now I'm rebuilding the motor.
I'm going to dump the car this summer and get a GS because I want to drive it and not worry about the boom every time I push the start buttom.
Tim

Vito.A

Both the LS3 and the LS7 are great engines. The LS7 does have valve guide issues as well as poor quality sodium filled exhaust valves. If you resolve those issues, it is a great cam and headers car. If you want to boost it, you have to be realistic and keep the boost level low because of the hypereutectic (cast) pistons, but this issue applies to the LS3 as well. The Z06 has a stronger rear end and is still a lighter weight car. At higher boost levels the LS3 does have more material between the cylinders that gives it a head gasket advantage. You should also upgrade the crank, rods, and pistons on an LS3 at high boost levels. Even with great bottom end components, just one hickup from the fuel system will fry the motor.

Since the C7 Z06 was intoduced, the real bargain out there is a used ZR1. Already boosted in a well balance package with the lightweight alum frame. Just a set of headers and a pulley and these are great cars.

Cor430vette

Agreed^^^get the Zr1


I always read about the Z06 being so much lighter than a grandsport but from what I read were talking about what 100 to 150 lbs max?
Everything helps, but throwing a valve isnt worth the 150 lbs weight advantage especially if you can add allot more HP to the LS3 without throwing a valve.
The Z06 is a disappointment honestly, because it was the premier vette ..now its just a ticking time bomb....kinda like the S65 engine in a M3 it has connecting rod bearing clearance issues that cause their engines to blow up too...thats all they talk about on the M3 forum. Huge amount of threads, that is why I sold mine and bought a grandsport.

SlayerRX8

If you plan to keep the car long term, you may want to sell your LS7 to someone who needs an N/A motor and get a different block.

I still think the LS7 is great as a bolt on or N/A motor. But there's a reason I have an LS2 instead. It will be boosted.

EvanZR1

i went with a fully loaded manual GS and put a blower on it for significantly less than a similar Z06 or ZR1, but that was buying new. I'm very happy with my 600RWHP GS, but if I were looking now (used), I'd go with a ZR1.

xBoostx

You are absolutely rite, a buddy is making 940 whp with a stock LSA short block and 6L80 transmission in a Lexus SC 400 stock LS3 heads (no porting) single turbo 20 psi.

Beat a 1200hp twin turbo Lambo, 1000 hp porshe the list goes on .

JCox23

Used ZR1's are still in the $60-70's range. I'm looking at trading my car for a '13 auto GS with A&A V3 kit already on it with Snow Performace meth system, Pfadt headers and H-pipe, Ron Davis aluminum radiator and a lot more and they're asking $50k. Hard to beat a deal like that!

Cor430vette

Do it...

GeneSch

Anyone ever take the LS7 out and put a LS9 in the Z06? I was thinking if I ever needed to replace the LS7 I would just go to different block.

dev1360

I'd do the GS for the targa top lol.

I love the idea of the LS7, but the execution isn't quite there. The LS3 will ultimately make more power, more reliably.

MUKAK

what was done to your heads? my heads are also redone and i am still afraid

RamAir972003

Can you elaborate on more about your heads being redone....im at 16k on mine and still running strong. Who did them what parts were used and so on.