LS7 vs. 350 ci LT5 mods

[Kevin]

Originally Posted by Paul Workman

Not taking anything away from the C6 Z06 - I'll bet with its weight it would be a hoot to drive. But, back to big motors, I believe FBI'ers - Bob G, Al, and Kevin all built a 427, and two 441 LT5s - all of which would blow an LS7 away across the board. And, the tag was more like $20k - quite a bit less if you did your own porting and disassembly and reassembly.

The nice thing about building a big inch LT5 is much of it can be done in phases - providing some nice performance boosts along the way: porting the top end and timing the cams, and installing headers, for example, could net you a 500 hp 350. All those base pieces would transfer to the big boy (with some further porting and bigger valves, perhaps) so nothing is lost. With the sleeves and portability of parts, the LT5 becomes close to "modular"!

Sorry...My enthusiasm is leaking out again

P.

I would hope that a heavily modded car will be faster then a stock car. I love the ZR-1 but modding it is becoming cost prohibitive. $10,000 to get mid 400 hp is insane

[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.

[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.

[Paul Workman]

Originally Posted by XfireZ51

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.

True, but there's where the cubes are making a difference. What I find delicious (if that's a word for engine technology) is the overall comparison of their architectural respective power/torque curves.

As for $/hp, argument, to get from a stock LT5 to a 427 LT5 it could be said that the $$ it would cost today to sell a stock ZR-1 and purchase a C6 Z06 would be pretty close, if not in favor of the LT5. (However, the $$ outlay could be substantially cheaper for the LT5 if you do most of you own work.) So, once you have arrived at displacement parity, let the mod vs mod comparisons begin!

But, that said, the C6 Z06 option also brings with it a modern performance chassis - sporting an aluminum frame and some titanium here and there too. Add to that the new fuel economy requirements and the C6 Z06 with all the trimmings (LS7) may become history and thus one day be the apple of the eye to those like us ZR-1 nuts that appreciate those "pinnacle" examples of Corvettes. So, maybe now would be the time to buy one al la the L88s of their day?

Back to the topic, Marc advertises a 415 LT5 package that makes 600+ hp. I found a dyno graph of such an engine on his web page, and compared to the LS7 architecture, the differences are striking and quite exciting especially when considering there is still a 12 ci disadvantage to the 415 motor!





It begs one to wonder what might have been possible were there big inch heads available for the LT5, where the practical rpm limits might have been...doanit!

I believe this pair of graphs makes the point that Bob G is talking about when he describes the reason why it takes 25+ hp "peak" advantage over an LT5 car for the LS cars to be competitive.

All very interesting...

P.

[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

[Pete]

You boys need to remember the LS7 has 77 more cubes.

Pete