Why the LT1?

[Stallion]

I see that it seems to be good to have an LT1 block in your Vette and I was just wondering what made it that much better than most small blocks (it's a small block, right? If I remember correctly it's a 350 ci?).

Thanks!

TR

 

[LT1Vettepilot]

Well everyone calls it a 350...technically its a 346...but hey, who's counting

Depends on which LT1 you are refering to...wether it be the earlier LT1s from 1970-1972, or the newest version, the 1992-'96?

I'm not sure about all the details, but the earlier LT1s had solid lifters, allowing for a higher max RPM. There may be some more reason behind the earlier ones, but they are beyond my knowledge.

The new LT1s, from '92-'96, also have a raised redline over it predesessors, plus the big advantage is the reverse cooling. Meaning, coolant is routed to the heads first instead of the block. this permitted higher bore temperatures and reduced ring friction, and helped cooling around the valve seats and plug bosses.

This information came from the Corvette Black Book (and you just thought I was one smart cookie! :L)

I have some more information around here about the later LT1 and the LT4...just not sure where. I think it may go into a little more detail about the newer engines. Someone have more for the earlier ones??


Oh, and yes it is a small block...

And just to get your mind off onto another tangent...the LS1 and LS6 improved upon the late generation LT1 significantly...that engine, however, is beyond much of my realm of knowledge!

 

[BigBrakeFuelie]

From what I understand and have learned is that it is a very high performance engine..
The LT1 combined Rat Like Muscle with nimble handling.Most Big Blocks because of the extra weight didn`t handle as well.The LT1 produced 370 BHP in 1970.That more than one HP per cubic inch.
Corvette equipped with the LT1 achieved a 50/50 front/rear weight balance.
The LT1 was spring off of the old Z28 engine.Both engines were solid lifter small blocks with High winding potential.
The 370 HP. arrived at 6,000rpm. max torque was 380ft.lbs. at 4,000 rpm.
Also Corvettes with the Lt1 came with a stiffer supension.Legend has it the Lt1 Corvette out HANDLED a Porsche 911E for MotorTrends comparision.

 

[Stallion]

Okay, thanks for the information and reply. So I guess that it's good to have an LT1. I'm looking at C3s, so I'm referring to the earlier ones.

>> And just to get your mind off onto another tangent...the LS1 and LS6 improved upon the late generation LT1 significantly... <<

But weren't these engines big blocks (454 ci)?

Thanks again!

TR

 

[LT1Vettepilot]

Yes, the earlier (C3) LS6 engines were big block 454s...I don't believe the LS1 designation was used until the 1997 Corvette came out with it. The LS1 and the newest LS6 (in the ZO6)are both still a small block 350s.

 

[DkBG]

As for your questions on the early LT-1 , it was based on a four bolt main block . It had 2.02" intake valves , which were the largest you could fit into smallblock heads . Along with the solid lifters it had a more radical cam . It was close or maybe the same as the Duntov 30-30 cam . It was factory fitted with a Holley 780 Dual feed carberator on an aluminum "cross-H' intake manifold . Down in the oilpan ,it had a windage tray to keep the crank from haveing to fight its way through extra oil that splashed up from the pan . The exhaust manifolds were slightly better than some of the other engines but not exclusive to the LT-1 . I don't remember for sure but it may have come with a factory dual point ignition . Thats all I remember now . Hope this helps . Cliff

 

[Stallion]

Hey, thanks a lot for all of those specs, Cliff. That does sound like a real nice block to have. Maybe I'll be an owner of a C3 LT-1.

TR

 

[tonyk72]

HP figures for Corvette LT-1's
1970 has 370 HP gross
1971 has 330 HP gross/275 net
1972 has 255 net

Camaro LT-1's
1970 has 360 HP gross

"Zora picked the 302 small-block planned for use in the Z/28, made a few modifications and turned it into a legend, which debuted in 1970.
The LT-1 was a hybrid between the 302 and the 350, In essence, the engine was a 302 with a 350 crank."

all info found in Corvette & Chevy Trader Feb. 2001 issue

 

[LIRacer]

What did the 71 and 72 have different to reduce the HP to 255 net from 275 net?
Does any have performace numbers for the 3 years of the real LT-1?

 

[tonyk72]

Here's a link within this forum that goes into the differences between a '71 & '72. Basically, the '72's ignition & valve timing were retarded and the transistorized ignition was out the window...

http://www.corvetteactioncenter.com/forums/showthread.php?s=&threadid=7770

 

[jmp]

sorry, 346??

Well everyone calls it a 350...technically its a 346...but hey, who's counting

Just curious... where do you get that number from? The bore is 4.00, the stroke is 3.48... That equals 349.849 ci.

 

[69autoXr]

technically it's a 346...

I think he's getting it confused with the LS-1/LS-6, tecnically those are 346 ci.

 

[Erik S. Klein]

Why an LT-1

I think the real reason I ended up with an LT-1 was the overall ballance of the car.

When I started looking for a Vette I knew I wanted a C3 and I was certain it had to have chrome on both ends. Initially I was pretty sure I was going to get into a 454 convertable but after doing a little research I realized that the 454, while a very strong engine, wasn't that much of a better performer then the LT-1. It does win in a straight line, of course, but because of the extra weight out front the handling and braking of the LT-1 is superior.

When I was shopping I was thinking of competing with the car (autocross, mostly) and felt that the handling would be a bigger factor then the acceleration.

In the end I never raced my car (unless I saw a mustang in need of a lesson) but I still enjoy having the extra power and quick winding of the LT-1 when I need it.

 

[Robert N]

Erik, nice car.

Mine is a NOM 1970. In the case of the 1970, the LT-1 is as fast or faster than the 454. HP rating was 390 for the 454 and 370 for the LT-1. The overall weight and distribution made up that gap very well.

 

[Erik S. Klein]

In 1972 the 454 was rated at 270 HP and the LT-1 at 255.

The big difference was where they reached their peaks. I don't have the numbers in front of me but I'm fairly certain that the LT-1 was pushing peak HP at a significantly higher RPM. The 454 also had more torque.

Still, the performance of the LT-1 was far more general purpose where the 454 was more of a straight-line runner.

 

[Stallion]

Re: technically it's a 346...

I think he's getting it confused with the LS-1/LS-6, tecnically those are 346 ci.

Isn't the LS6 an engine option only offered in '71 which is a big block 454? 425bhp and pretty rare. I thought that the LS6 (as well as LS5) is a big block? Right?

TR

 

[69autoXr]

Yes, you are partially correct. The LS-6 designation was originally used in 70 and 71 for big block 454 engines, only offered in the Vette in 71. Chevy resurrected the LS-6 designation for the engines used in C5 ZO6's, and that is what I was referring to about the 346 ci. Chevy has reused old designations several times, not only with the LS-6 but also the LT-1, ZR-1, and of course the Z06 designations.

 

[Brett]

Erik, are you saying the '72 454 had more torque than the '70 454?

 

[Brett]

If I remember correctly, the the main difference in horsepower came from the compression ratios. I'm talking 1970 here.

The LT-1, while a smaller block, had a much higher compression ratio (12.5:1?) than the 454 (10.5:1?), hence the minimal difference of 370 to 390 horse between the two. They had originally planned on making a high output 454 as well, with something like 450 gross horsepower, but it was never released, which is a shame. However, not all of the LT-1's had 370 hp. There was also a lower compression LT-1 with 350 horse. You can see the trend, and that they obviously wanted four engines--high output versions of both. I would be interested to hear whatever happened to that hot 454.....

Anyway, the 370 hp LT-1 engine is much rarer than the other two, and worth a pretty penny.



Brett

 

[Robert N]

The LT-1 was only offered in 1970 as the 370 hp, 380 torque. The 350 hp was the L46 designation.

The 1970 LT-1 offered a solid lifter setup and 11:1 compression, high rise aluminum intake larger holley carb, larger exhaust (2 1/2) accounting for the power. By all true accounts, the 1970 LT-1 was closer to 425 gross hp. The LT-1 has run the 1/4 in 13 sec at over 105 mph supporting the claim.

The only common point with the L46 and the LT-1 was the the 11:1 compression.