LS7 vs. 350 ci LT5 mods

[XfireZ51]

No doubt in my mind that $4$, the LS7 is hard to beat for mods. You start out at 505hp, headers and a tune and you're looking 550 at the crank. I have a friend with a Silver 07 Z in that configuration. Not to mention it looks like a Great White coming up on your 6 when viewed in the rearview mirror. For a 5.7L, the LT-5 responds incredibly well to even small mods like porting and better exhaust. So the potential is there but the
OHV v OHC differential will always be low end torque which the LS-7 has in spades. Of course, we'll need to see what Todd has cooked up with his 427.

[Paul Workman]

It is becoming obvious that the torque curves on the LT5s are characteristically flatter over all, and especially at the high end. (See how for the most part the LT5s hp is more or less flat going into 7000 rpm, even on stock cams?)

The trouble with "peak" hp and torque numbers is, well, they're "peaky". The greater area under the curve(s) makes more sense when evaluating usable output.

Just food for thought.

P.

[Kevin]

anyone have dynos of 368 or 385 cars?

[XfireZ51]

Originally Posted by Paul Workman

It is becoming obvious that the torque curves on the LT5s are characteristically flatter over all, and especially at the high end. (See how for the most part the LT5s hp is more or less flat going into 7000 rpm, even on stock cams?)

The trouble with "peak" hp and torque numbers is, well, they're "peaky". The greater area under the curve(s) makes more sense when evaluating usable output.

Just food for thought.

P.

But Paul, the LS7 doesn't drop down to our level of torque until 7K. Up to then, its always higher than the LT-5.

[Locobob]

Originally Posted by Kevin

anyone have dynos of 368 or 385 cars?

LPE 368

The pull with the higher peak numbers is the result of more aggressive plenum and injector housing porting along with installing an SRP underdrive pulley set.
As you can see the power curve generally moved upward with the loss of some low end torque... as one would expect from a more aggressive intake tract.

[Locobob]

This one is a comparison of mildly modded engines of similar power showing the area under the curve for a 4th gear pull (speed not rpm graph). Anyhow you can see that the LT-5 HP curve is flatter than a comparable power LS-1.

[Locobob]

Frank: Why is your 441 only 11-1 compression??? Wonder what the power difference would be using the more popular 12-1 ratio.

[XfireZ51]

Bob,

Looks like they didn't do a bad job mimicking the LT5 power curve with the LSx motor. The first dyno looked like it was running a bit fat.

[Locobob]

Originally Posted by XfireZ51

Bob,

Looks like they didn't do a bad job mimicking the LT5 power curve with the LSx motor. The first dyno looked like it was running a bit fat.

I deliberately picked the motors so that they were close in peak hp and then used what I deemed to be reasonable red lines for shift points. The graphs are indeed close up until shut down time for the LS - had it continued I'd think you'd start to see it nose over big time. My basic point of this comparison is that the LT-5 lets you hang on a bit longer resulting in more power under the used curve.

[Nacho_ZR1]

Originally Posted by Kevin

I love the ZR-1 but modding it is becoming cost prohibitive. $10,000 to get mid 400 hp is insane

I agree with this 10000 percent! So much so that I decided to stop modding my ZR-1 after it comes back from Corey's with the Jeal headers, 4.30 gears, and newly tuned chip. I was going to start saving up my pennies for a 415cu but then I found this and brought it home for $7k earlier this afternoon:





It was too good of a deal to pass up. All she needs is paint! It's a 64 SS Nova with a "tiny" 406cu small block. Supposedly it's running the 1/4 mile in the 8.80's but I'll confirm that in the spring