Destroked, Boosted LS7?

[madmax]

Hi ya'll,

Been looking for a new powerplant for my '05 GTO. Looking to do something a little different. Anyone have any experience with destroked LS7s? I don't know if the 6L80E could deal with those kinds of revolutions, but a boosted motor spinning to 8500rpm with turbos to make up for the torque under the curve seems like it would be a lot of fun.


Max

[Ron.in.SoCal]

Hey Max - LS7 owner here, but have no experience w your idea. Not even sure you would need to destroke it but those blocks generally don't like much boost. Sounds to me like you might be better off starting w a resleeved 4.125 bore block for strength, six bolt heads and a solid roller set up. There's quite a few boosted motors on LS1tech, and a few that took the turbos off and went larger cubes. Good luck!

[INTMD8]

What are your goals?

No need to de-stroke it for 8500rpm but you're looking at aftermarket block/solid roller/sheetmetal intake/etc. If you had a turbo system capable of efficiently working at that rpm you are talking about a 1500+++rwhp combination and it isn't going to be a very fast spooling combo. (think twin PT7675's).

If you run a smaller pair of turbos for faster transient response it will choke before 7k much less 8500.

Did you swap a 6l80 into your car? Either way this combo would turn a 4l60 or 6l80 into shrapnel almost immediately.

[madmax]

Goals for the car:

Project GTO6 - the car GM should have made - a la Corvette Z06.

I'd like to get around 800hp out of it at the max (at the flip of a switch, probably keep it a lot more tame for normal driving). I need to be able to hang with pretty much anything on the road with no problems (low 10s). Going to tub the car etc. I'm looking to make it my 'tuner' car - turbos and such. Even a Racelogic system when I get the green. I considered going SC with a TVS but I don't think I could live without the power under the curve.

I'm looking for a 'different' sleeper combo. I could stroke the motor, a la 402 but I think building something that would spin up really, really fast, scream, and hopefully paddleshift would make it GTR-like. Turbos love automatics. Who would expect a GTO screaming at 8k? I just want something fun to drive.

I have been looking into the 6l80 swap but is complicated. I think I will be forced to go to TCI for their 6 speed but it is 5k (dealbreaker) or something like that where a 6l80 can be had for a grand.

@Ron: You're right. Probably the right thing to do.... LS7 just sounds better.


Thanks for the replies.



Off topic: Is there any way to mate a dual-clutch tranny to said engine?

[madmax]

Forgot to mention the car has an STS 67mm rearmount single turbo right now. Takes a little while to spool but that was OK for a while. Car made 475/491 on 7.5lbs conservative tune could make a lot more with meth and 10lbs.

[andrewb70]

.....

Off topic: Is there any way to mate a dual-clutch tranny to said engine?

Yup, it's bolt in, just add cash, skill, and machining equipment.

Andrew

[madmax]

Yup, it's bolt in, just add cash, skill, and machining equipment.

Andrew



........okay?

[INTMD8]

I'd like to get around 800hp out of it at the max I considered going SC with a TVS but I don't think I could live without the power under the curve.

I'm looking for a 'different' sleeper combo. I could stroke the motor, a la 402 but I think building something that would spin up really, really fast, scream, and hopefully paddleshift would make it GTR-like. Turbos love automatics. Who would expect a GTO screaming at 8k? I just want something fun to drive.

I have been looking into the 6l80 swap but is complicated. I think I will be forced to go to TCI for their 6 speed but it is 5k (dealbreaker) or something like that where a 6l80 can be had for a grand.

@Ron: You're right. Probably the right thing to do.... LS7 just sounds better.


Thanks for the replies.



Off topic: Is there any way to mate a dual-clutch tranny to said engine?

Again, if you're talking about a turbo combination on 400+CI that will spin to 8000+rpm, it is not going to have fast transient response down low.

Realistically an efficient fast spooling 800rwhp and 400ci twin turbo setup is going to see 7000rpm max.

6L80 isn't going to live very long, if at all at 800rwhp. Most C6 vette and 5th gen Camaro guys making that kind of power are swapping to 4l60's and 4l80's if that tells you anything.

If the TCI 6-speed is out of your budget I would say any dual clutch setup that will take that kind of power will be out of your budget times 6 or so? (just a guess)

[madmax]

Yup, it's bolt in, just add cash, skill, and machining equipment.

Andrew

I didn't mean to jump all over you. What transmission would be best? I know it's probably a pipe dream but stranger things have happened. I figure a porsche tranny or something of the like that can handle a decent amount of power? There must be one that is fairly plentiful somewhere.


Max

[madmax]

Again, if you're talking about a turbo combination on 400+CI that will spin to 8000+rpm, it is not going to have fast transient response down low.

Realistically an efficient fast spooling 800rwhp and 400ci twin turbo setup is going to see 7000rpm max.

6L80 isn't going to live very long, if at all at 800rwhp. Most C6 vette and 5th gen Camaro guys making that kind of power are swapping to 4l60's and 4l80's if that tells you anything.

If the TCI 6-speed is out of your budget I would say any dual clutch setup that will take that kind of power will be out of your budget times 6 or so? (just a guess)

That's why I was thinking about going the destroked route. With a larger bore I could use a shorter stroke and still maintain a decent amount of cubes (as opposed to doing the same to an LS1). Probably about the same as my current stock LS2 with the advantage of a shorter stroke and insane operating range.

My idea is that since the engine is smaller, I could map the turbos to spin up and give me pretty much what I'm looking for at all times (less oomph needed down low than say a 418ci LS3 stroker).

I may just have to wait to do the TCI route and do it right. Or have some fun and blow a 6L80E up.

And re: dual-clutch, a man can dream.....

[andrewb70]

I didn't mean to jump all over you. What transmission would be best? I know it's probably a pipe dream but stranger things have happened. I figure a porsche tranny or something of the like that can handle a decent amount of power? There must be one that is fairly plentiful somewhere.


Max

Max,

You did not jump all over me. In fact, if I continued to post anymore, I would just come off as a jerk, and I did want to do that.

I am not sure that you fully understand what you are asking here. Just the words "destroke a LS7" already imply a $25,000 dollar engine. Then you start talking about forced induction and dual clutch transmissions. The forced induction is not new, but a dual clutch transmission, really?

Please don't take this personally, but whenever anyone starts talking about having 1000RWHP it is a red flag that they are completely clueless as to what that actually entails in terms of engine components, tuning, and driveline requirements.

Be honest, what is the most powerful car that you have ever driven so far?

Andrew

[madmax]

Max,

You did not jump all over me. In fact, if I continued to post anymore, I would just come off as a jerk, and I did want to do that.

I am not sure that you fully understand what you are asking here. Just the words "destroke a LS7" already imply a $25,000 dollar engine. Then you start talking about forced induction and dual clutch transmissions. The forced induction is not new, but a dual clutch transmission, really?

Please don't take this personally, but whenever anyone starts talking about having 1000RWHP it is a red flag that they are completely clueless as to what that actually entails in terms of engine components, tuning, and driveline requirements.

Be honest, what is the most powerful car that you have ever driven so far?

Andrew

I'm pretty sure I understand.

Thanks

[INTMD8]

First let me address the topic of de-stroking. Shortening the stroke will do nothing to increase the operating range of the engine. It will be limited by turbo size and valvetrain components no matter if it's a 4 inch stroke and 4.125 bore or 3 inch stroke and 4.125 bore.



a boosted motor spinning to 8500rpm with turbos to make up for the torque under the curve seems like it would be a lot of fun.


This statement is contradictory. If you have a set of turbos on any engine that efficiently makes power at 8500rpm they will not spool fast enough to give you any real "torque under the curve". It will be relatively laggy/peaky probably not making peak boost until 5500-6000rpm and a bit soggy under that RPM.

On the other hand, an LS motor with a relatively quick spooling turbo system is going to make peak boost by around 4000rpm and sign off at around 7000rpm or less.

With an LS motor and conventional turbo setup you'll need to trade one for the other, (quick spool/moderate rpm/slow spool high rpm).

Quick spooling turbos with strong low/mid rpm torque curve and efficient power at 8500rpm is not reasonably attainable.

[madmax]

First let me address the topic of de-stroking. Shortening the stroke will do nothing to increase the operating range of the engine. It will be limited by turbo size and valvetrain components no matter if it's a 4 inch stroke and 4.125 bore or 3 inch stroke and 4.125 bore.

I apologize. I should have clarified - that is one thing I found out at the beginning of my research. The shorter stroke would allow the engine to spin faster, reducing the rotating mass, correct? Some people place more weight on this than others, but the idea of a short stroke with lightweight materials seems appealing to me. The high operating range is a separate idea. But thank you for clarifying that.

I currently have a moderate rpm spooling system and it leaves something to be desired. My hope was there was a way to get the turbos to give me torque, let the motor take over and then use the turbos. If it's not feasible, like you others have suggested, a stroked LS3 418 might be the way to go.

Thanks for the info

Max