Destroked LS7?

D

Greg

I am just curious to get some opinions on this with the SL-C in mind specifically.

Has anyone considered using something like a destroked LS7 in their build? Given the SL-C's light weight, it doesn't really need a mountain of torque down low. Would it be better to destroke the engine, increase the rev limit and move the torque curve? I've been looking around and reading about it on some other sites but I wanted to consider the application in a 2400 lb. SL-C specifically. I would think the after market valvetrain options should be capable of 8000rpms or so over an extended lifetime (not drag racing).

Personally I like revs, any thoughts?

What were the gearing options on the Griffin gearboxes again? :shy:
 
E

Alex

I don't see why? Sub-2500lbs is not light as a feather - my cobra is 2120 with a half-tank of gas, 490RWtq, and I could use more. It's not like the power to weight is 1:1 ...... not to mention greater valve-train wear and tear.

But that's just me :D
 
D

Greg

I know you're a fan of big cubes. Do you even use first gear in your Cobra?

The valve-train would be one of my concerns but I don't think 8000rpms is out of the question. I was looking at the Katech Sneak Attack engine as an example and it seems it could be improved upon. Intake choice would come into question, I don't know if ITBs would almost be a requirement. I haven't done any math yet but was just spit balling, maybe a 4.155"x3.5" bore and stroke? Is this strictly solid lifter territory?
 
Last edited:
gt40fran

Fran Hall RCR

The 416 ci LS3 I have has proven to be a good little engine and makes good power, without breaking the bank...and its 11.1 so pump fuel is still usable...
 
D

Dean Lampe

I think to make an engine live at 8000 rpms (or at least between rebuilds) you need to use very light internals like the LS9 stuff. The valve train will need titanium parts wherever possible and you have to have high rpm accessories with no AC.
 
J

JordonMusser

Cubes are king, there is no logical reason to reduce the displacement of an engine unless it is rule related.

8000rpm is doable with good parts even at 427ci. valve strain stability will be your biggest problem. Valve springs wont last long.

You will want to invest it lightweight parts, and high quality springs. Ti valves, etc. Even getting optimized rockers (shaft rockers) and light weight push rods all helps. 8Krpm small block=sexxy.
 
gt40fran

Fran Hall RCR

Single 4 barrel...runs on E85...807hp with the small cam and 895hp with the real one....

I think there are pictures already on the forum somewhere..
 
D

Greg

EFNFAST said:
Yes - it's not too hard to do unless your interpretation of driving is stabbing the throttle like a madman.
Click to expand...

This is true however I don't want to feel like I have to tip-toe around 1st either. I'm not talking about cruising, I'm talking about driving in anger under hard acceleration. Do you just light em up? If you can't put the power down, it's a waste. That would be my concern.

I would definitely plan to keep it 11:1-12:1 compression to keep it on pump gas with relaxed cam specs.
 
D

Grant S

Dark Regent said:
This is true however I don't want to feel like I have to tip-toe around 1st either. I'm not talking about cruising, I'm talking about driving in anger under hard acceleration. Do you just light em up? If you can't put the power down, it's a waste. That would be my concern.

I would definitely plan to keep it 11:1-12:1 compression to keep it on pump gas with relaxed cam specs.
Click to expand...

its all in the mix with big HP and torque you'll have to find the right gears and very sticky tires. My SC Cobra was a tire burner until I found the right tires and gears then the whole car changed from scary to drive to scary fast and controllable. Although breaking the tires loose at 80 mph does give you a warm fuzzy feeling ;). And it all depends what your doing with it street or race ?
 
Z

Ben

Is this the same car? If so, and you want more photos, PM me.
 

Attachments

  • IMG_4056.jpg
    IMG_4056.jpg
    194.9 KB · Views: 705
C

Dusty

GT40s Supporter
I had the same mentality.."wouldn't it be cool to destroke my LS6 down to around 5.0L put in some Ti conrods, valves, Beryllium guides, etc." I called Crower one day on a whim, and it turned out to be cost prohibitive. They quoted me at around the $27k mark. Your best bet is do like the Daytona guys. Find a 5.0l Coyote motor and tune it up, or a early 2000s Chevy/Pontiac motor that was used in a Crawford chassis etc. Or a nice BMW E92 engine. They're popular.


Look for Perry on the forum. He's an LS7 wizard. That guy is building some monster 1200+hp "CAN-AM" twin turbo.
 
D

Greg

Yeah, reading around on LS1Tech and Corvetteforum it looks like the valve-train would definitely be the Achilles heel of the build. The thing I like about the destroked LS7 idea is that even with the reduced displacement you're still looking at something around 6.2L or so depending on the final sizes of the bore and stroke. That's not exactly small compared to the 5.0L Coyote and the 4.0L S65.

You're right about the cost, it would be a $20k+ engine when said and done taking into consideration the oiling system, custom intake, etc. With some Morel Short Travel Hydraulic lifters (don't remember if Stage7 is running these), some good shaft rockers, etc. it looks like 7000rpm can easily be cleared but I have no idea how high you can go before reliability goes out the window.

Another alternative I've been curious about would be the possibility of adding a VVT cam phaser to an LS7. I know Mast's got one but they haven't posted a dyno comparing it to their non-vvt LS7. All they have to compare are peak power numbers which are almost useless. I don't know if the springs necessary to prevent valve float on a high revving LS7 would be to powerful and prevent the phaser from working properly. This seems to be an issue with the GM VVT solution.

Right now I'm just enjoying reading about what other people have done and where they succeeded or failed while I wait til I get a chance to build one. I do know I don't want some dyno queen/drag only setup. I'd like something that matches what I'd like to do with the car which would ideally be a street/road course setup. However, I'd still like to have something a bit unique that suits me, not some off the shelf option.
 
B

Ben Whittle

Dark Regent said:
Yeah, reading around on LS1Tech and Corvetteforum it looks like the valve-train would definitely be the Achilles heel of the build. The thing I like about the destroked LS7 idea is that even with the reduced displacement you're still looking at something around 6.2L or so depending on the final sizes of the bore and stroke. That's not exactly small compared to the 5.0L Coyote and the 4.0L S65.

You're right about the cost, it would be a $20k+ engine when said and done taking into consideration the oiling system, custom intake, etc. With some Morel Short Travel Hydraulic lifters (don't remember if Stage7 is running these), some good shaft rockers, etc. it looks like 7000rpm can easily be cleared but I have no idea how high you can go before reliability goes out the window.

Another alternative I've been curious about would be the possibility of adding a VVT cam phaser to an LS7. I know Mast's got one but they haven't posted a dyno comparing it to their non-vvt LS7. All they have to compare are peak power numbers which are almost useless. I don't know if the springs necessary to prevent valve float on a high revving LS7 would be to powerful and prevent the phaser from working properly. This seems to be an issue with the GM VVT solution.

Right now I'm just enjoying reading about what other people have done and where they succeeded or failed while I wait til I get a chance to build one. I do know I don't want some dyno queen/drag only setup. I'd like something that matches what I'd like to do with the car which would ideally be a street/road course setup. However, I'd still like to have something a bit unique that suits me, not some off the shelf option.
Click to expand...


1UZFE no? 4L, high RPM redline, freaking tiny and lightwight though admittedly difficult to get lots of power NA, potential up to around 1000bhp FI though. Cheap as chips!
 
M

MeLoN

Dark Regent said:
Yeah, reading around on LS1Tech and Corvetteforum it looks like the valve-train would definitely be the Achilles heel of the build. The thing I like about the destroked LS7 idea is that even with the reduced displacement you're still looking at something around 6.2L or so depending on the final sizes of the bore and stroke. That's not exactly small compared to the 5.0L Coyote and the 4.0L S65.

You're right about the cost, it would be a $20k+ engine when said and done taking into consideration the oiling system, custom intake, etc. With some Morel Short Travel Hydraulic lifters (don't remember if Stage7 is running these), some good shaft rockers, etc. it looks like 7000rpm can easily be cleared but I have no idea how high you can go before reliability goes out the window.
Click to expand...

A junkyard 4.8L or 5.3L engine with stock bottom end and decent valve springs will do 7K all day long. Add Isky EZ-Roll's or Jesel's and shaft rockers and a cam 8K is no problem. $5K max. Add in twin GT3582R's (another $1K-$2K) you can have 8K and 700-800 reliable horsepower (cxracing, turbos, IC's, etc) on pump. If you wanted to go nuts custom scat crank rods and pistons and +1000hp for under $10K. If you wanted to go completely nuts RHS block and LWS heads, yeah, $20K.

The rod angle and ratio on the bigger stokes limits RPM, so you need exotic race blocks and forged reciprocating internals. The smaller displacement throw-away junkyard truck motors will spin. The iron blocks add ~75lbs. I like big torque early on heavier cars. Big torque and HP at high rpm on something lighter is way more fun on a track IMO.
 
You must log in or register to reply here.
Back
Top