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L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

C4 Corvette LT1 Bone Stock

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Old Yesterday, 09:51 PM   #21
Tom400CFI
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Originally Posted by ddahlgren View Post
The logic is rather simple as a L98 has a decent torque curve with 10 more ft.lbs. There is a myriad of gear choices as well from I believe 2.59 to 3.43 for the stick car.
With a '91 L98 stick shift car, there is one rear axle ration option. Neither 2.59 nor 3.43 are it.



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Originally Posted by ddahlgren View Post
You enter driver skill level as another variable so anywhere from a 5.8 to 6.5 might all be a valid 0-60 ft. time.
You enter driver "skill" and suddenly there is no limit to the range of possible times. The OP asked what the CAR can do. So to eliminate "Driver skill", which ranges from guys like Evan Smith, Jamie Furman and Ranger...to the guy that launches at the drag track in reverse...we look at what the best results are from that CAR, and then we can see what the CAR can do. When we do this, we typically try to examine a car as close or exactly like the one being asked about; a '92 LT1 stick. We don't typically go looking for cars with different engines and then try to extrapolate data from something with 55 less hp and apply it to something else.


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Originally Posted by ddahlgren View Post
Tires and surface enter it as well and there is no such thing as a corrected 60 ft. time. At least with a dyno you correct for weather and there is no 'driver skill level'. For me calling it a 6 second 0-60 on an average day with an average driver on a typical surface is a realistic number. The sad fact is around 50% are easily faster in 0-60 times under the same conditions. I don't think anyone with eyes open buys a C4 thinking it is a wildly fast car but because they like the lines and has plenty of room for improvement if local smog regs allow it.
We're talking about the CAR..what the CAR can do. Who said it was "fast"? What does that mean, anyway? I bought my C4 b/c it was fun.


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Originally Posted by ddahlgren View Post
What might be interesting would be to see the raw torque numbers off of an early 350 hp. 350 and a L98 and LT1. I do find the reuse of LT1 as an engine designation a bit curious as I had thought that was used in the 70's for the 350 hp. 350.
'70 was an LT-1, '92 is and LT1. Here is the LT-1 350 vs. LT1 350 vs. L98 350 comparison. The LT1 wins that shootout.

Name:  LT1 vs LT-1 vs L98.jpg
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Old Yesterday, 10:35 PM   #22
ddahlgren
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Are those numbers corrected or not? They are so close to published numbers that I would think corrected. I have run a 1970 LT-1 on a dyno and it made a good deal more than 300 hp. stock. It seems hard to believe they were 50 hp. wrong and in the ZR1 trim they were rated at 370 hp. and no idea what got them there.
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Old Today, 09:00 AM   #23
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and in the ZR1 trim they were rated at 370 hp. and no idea what got them there.
The ZR1 didn't have a LT1, it had a LT5. While the LT5 may have been a 350 CID V8, that was about the only things it had in common with the LT1.

http://www.zr1netregistry.com/Inform...gineSpecs.aspx

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Old Today, 12:16 PM   #24
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Originally Posted by 1stVetteFinally View Post
The ZR1 didn't have a LT1, it had a LT5. While the LT5 may have been a 350 CID V8, that was about the only things it had in common with the LT1.

http://www.zr1netregistry.com/Inform...gineSpecs.aspx
Have been comparing C3 lt 1 vs. C4 lt1 and yes there was a C3 ZR1
http://www.corvetteblogger.com/2008/...-Corvette-ZR1/
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Old Today, 01:10 PM   #25
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Originally Posted by ddahlgren View Post
It is no faster than any other 3400 lb car with 300 hp when new and how tired it is now only you know. I suspect 4.5 second 0-60 is venturing off to fantasy land. a 91 is advertised at 6.2 0-60 and seems about right.
the LT4 was tested at 4.9, don't think any stock lt1 will beat that.
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Old Today, 01:58 PM   #26
Tom400CFI
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Originally Posted by ddahlgren View Post
Are those numbers corrected or not? They are so close to published numbers that I would think corrected. I have run a 1970 LT-1 on a dyno and it made a good deal more than 300 hp. stock. It seems hard to believe they were 50 hp. wrong and in the ZR1 trim they were rated at 370 hp. and no idea what got them there.
Say....WHAT?? I have no idea what you're saying there. Do you? Where did the "ZR1 (ZR-1?) come from in this conversation?

I'm sure that you DID see more than 300 hp on a dyno w/an LT-1....just like you would also "see more than", if you put an LT1 on a dyno with open headers, no exhaust and no accessories.

It's weird to me that this needs explaining. The graph above was apparently done using "Net HP" rating; all accessories and stock type exhaust in place. How can we determine this? Well, the '70 LT-1 was originally rated at ~370 hp...yet in the graph it made ~300. The LT1 was rated at 300 net hp and it made 3-low teens in that graph -pretty close to it's net rating.


Now let us observe another test...this one would be more like the one that you must have ran where you saw "good deal more than 300 hp. stock." That would be a GROSS hp measurement with all accessories removed, open headers, no exhaust and optimized conditions, fuel and tune. Under these conditions, you'll see that the LT-1 and the LT1 both returned just about 350 hp, in THIS TEST

Bottom line? The '70 LT-1 and the '92 LT1 both made about the same power, how ever you measure it.

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Old Today, 02:14 PM   #27
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Say....WHAT?? I have no idea what you're saying there. Do you? Where did the "ZR1 (ZR-1?) come from in this conversation?

I'm sure that you DID see more than 300 hp on a dyno w/an LT-1....just like you would also "see more than", if you put an LT1 on a dyno with open headers, no exhaust and no accessories.
It came from the fact they also made a 370 hp (claimed) 350 between 70 and 72 that was a gen1 w/carb etc and came in a ZR1 C3 option. If the C4 LT1 has an electric water pump and the only electrical load is ignition injectors and water pump the A/C is off to rack for the power steering pump to drive I fail to see more than a couple of hp. of accessory load. We never ran a power steering pump or A/C unit on the dyno alternator was generally not connected with a carb no fan but did have the water pump connected. The reason I as about correction factors used is the date on the bottom of the sheet is 1990. A C3 would of had cast iron exhaust manifolds and doubt if GM is so silly to test without them. We always asked for the exhaust manifolds that fit the chassis and usually not nearly enough room for a complete exhaust system. But that is not 50 to 70 hp either. The difference between advertised and listed on that sheet is between 14 and 20 % and that is a pile that exhaust or accessory does not explain away.
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Old Today, 02:47 PM   #28
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Quote:
Originally Posted by ddahlgren View Post
Are those numbers corrected or not? They are so close to published numbers that I would think corrected. I have run a 1970 LT-1 on a dyno and it made a good deal more than 300 hp. stock. It seems hard to believe they were 50 hp. wrong and in the ZR1 trim they were rated at 370 hp. and no idea what got them there.

I understand what you are saying and wonder the same thing. Best I can figure is GM is using Trump math to promote what they want to.

For the two modern cars (engines), you'd have to think they were posting dyno numbers with accessories mounted. If they used stock manifolds, we also know 70s was way worse...handicapping their performance.

Even if GM "corrected" 1970's numbers (as shown here) to modern numbers, how did the peak change? And, why IS IT so much lower than expected. IIRC, 15% off pre-corrected HP numbers would drop the 1970 to something like 317hp @ 6k rpms. The graph isn't representative of either (peak location or amount).

I've often complained about these GM charts and this one is no exception.
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Old Today, 03:16 PM   #29
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Guys. THINK. See the independant, third party test I linked above? Where both engines were w/in 3 hp of each other? How can that be? If GM was TRUMPing up numbers, than how does the SuperChevy test come out with such similar results to the GM test?(other then the displacement of numbers created by the differing measuring methods of net vs. gross)


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Originally Posted by ddahlgren View Post
If the C4 LT1 has an electric water pump and the only electrical load is ignition injectors and water pump the A/C is off to rack for the power steering pump to drive I fail to see more than a couple of hp.
C4 doesn't have an electric water pump. It has a gear driven water pump, a belt driven PS pump, alternator and AC compressor pulley. It also has cast manifolds, cats, dual exhaust with three mufflers and factory tune. Saddled with that, it makes ~300 hp at the crank. Remove that (minus the water pump), instal LT headers and an optimized tune, and you get 350 hp at the crank...or at least Super Chevy did. There is your C4 diff between NET and GROSS hp.


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Originally Posted by ddahlgren View Post
We never ran a power steering pump or A/C unit on the dyno alternator was generally not connected with a carb no fan but did have the water pump connected.
Right. That is what we call, "Gross hp". You had to run the water pump b/c you can't over heat the engine. And you probably didn't have an electric sitting on the shelf.



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Originally Posted by ddahlgren View Post
The reason I as about correction factors used is the date on the bottom of the sheet is 1990. A C3 would of had cast iron exhaust manifolds and doubt if GM is so silly to test without them. We always asked for the exhaust manifolds that fit the chassis and usually not nearly enough room for a complete exhaust system. But that is not 50 to 70 hp either. The difference between advertised and listed on that sheet is between 14 and 20 % and that is a pile that exhaust or accessory does not explain away.
This is undecipherable. What does 1990 have to do with C3 exhaust manifolds?? Where do you get "advertised" and "listed on that sheet"? I think you're talking "Gross" vs. "Net"....but it's hard to tell. GM has PLENTY of room in their dyno cell for full exhausts; it's how they dyno every engine RPO that they produce. It's really hard to tell WTF you're saying, here.


If you take a '70, 370 hp LT-1 and install factory '70 LT-1 manifolds, full exhaust, alt, smog, FAN, and tune, you're going to end up w/around 300 hp at the crank...about what GM measured in that graph above.

Dude...you wondered earlier:
Quote:
Originally Posted by ddahlgren View Post
What might be interesting would be to see the raw torque numbers off of an early 350 hp. 350 and a L98 and LT1
I promptly slapped up a graph for you... FROM GM...from the horses mouth and now you need to argue about that too? While confusing yourself with net vs. gross hp ratings? Yikes.


Need more evidence that both motors make the same power? I think you do. HERE IS A TEST comparing a Porsche 911 and a '70 LT-1 'Vette. Look about 1/2 way down at the 1/4 mile results:
Quote:
With a quarter mile time of 14.36 seconds and 101.69 mph, the ‘Vette easily out-distanced the smaller-engined Porsche’s
Forget about the Porsche, and ignore the ET; we know that was hampered by tires of the day LOOK AT THE TRAP! 101.
And
is another data point, again just under 1/2 way down...
Quote:
1970 Corvette (CL)
350ci/370hp, 4spd, 4.11, 0-60 - 5.7, 1/4 mile - 14.17 @ 102.15mph
....I trap 101 here in UT (elevation) in a '92 LT1 which is a heavier car. How can that be, folks? If they aren't about the same hp...then how can that be?


.

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Old Today, 06:03 PM   #30
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Below are a couple of pages from GM 1992 advertising brochures.

One states that the LT1 has "the highest net horsepower for any production-car small block in Chevy history".

The other states it has a 50 hp increase from '91 and more power than the '70 LT1.




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