Chevy LT5 DOHC, 32v V8

The 1UZFE EGR Delete Kit is available for sale here.

cribbj

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I had never seen one of these interesting engines in real life, but Dennis has one in his shop to repair. Seems another shop tried to time it and bent a few valves.

Lotus & Mercury (Marine) designed & built these for GM back in the late 80's and early 90's for the ZR1 Corvette. It's supposed to be quite a motor, and they're pretty rare.

Here's what Wiki has to say about them (scroll down to the bottom): http://en.wikipedia.org/wiki/GM_LT_engine

http://en.wikipedia.org/wiki/Chevrolet_Corvette_C4
 

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very cool engine, i a zr1 came out here in to west texas for the Big Bend Open Road race a few years ago and thats when i learned of this engine, it sounded good!
 
This looks like it would be a really fun motor to play with. I'm normally not interested in domestic iron, but this has the cams in the right place, and enough valves to make it interesting.

After reading some additional tech stuff on it http://www.zr1netregistry.com/LT5tech.htm it really does have all the right stuff. Even secondary injectors! Can't understand why it was down on power, though. It's only rated for 375 BHP for a 350 in3 engine. Something wrong there - that should have been at least 400 BHP with all the Lotus engineering and go-fast bits that went into it.

Shoot, even our 1UZ's, with the lazy cams, and restrictive intakes, designed to power the luxo-barges make more than 1 HP per cubic inch.

Cool to see that it could rev to 8000 RPM, but the accessories couldn't survive at that level, so they had to give it a 7200 RPM redline.
 
I'm normally not interested in domestic iron,

It's only rated for 375 BHP for a 350 in3 engine. Something wrong there - that should have been at least 400 BHP with all the Lotus engineering and go-fast bits that went into it.

Shoot, even our 1UZ's, with the lazy cams, and restrictive intakes, designed to power the luxo-barges make more than 1 HP per cubic inch.

Well, its not iron and i believe they were rated 375hp the first year and 400hp later. As we have learned from dyno's the 1uz made around 235hp crank (180rwhp) therefore putting out 1.03hp per inch and the LT5 at 1.07hp per inch on the 375hp motor and 1.14hp per inch on the 400hp motor. Not bad keeping up with and exceeding the efficiency of a smaller motor.
 
I have seen one of these engines in a custom trike but I can't find the photo's now, it was ll polished up and took me ages to find out what the motor was from.

Must have been too complicated for the American market...... stir.
 
Must have been too complicated for the American market...... stir.

Apparently, but probably not quite in the way you think, Andy :)

Here's an excerpt I found on another website from a book by retired Corvette Chief Engineer, Dave McLellan called "Corvette From the Inside"

"Why the Gen III Doomed the LT5

The contrast between the Gen III [LS1/LS6 engine] and the LT5 engine is striking. The LT5 is both taller and wider, as a result of its double overhead-cam cylinder heads and its complex intake manifold. It became apparent that the next generation Corvette, if it were designed solely around the Gen III small block, could be significantly smaller and lighter than if it had to accommodate the LT5 engine.

Studies based on a large population of modern cars have given us the standard relationship between engine weight and total vehicle weight. Increasing an engine's weight by one pound means that the total car's weight will likely increase by two pounds. We estimated that taking 80 lbs out of the Corvette's engine would allow us to remove another 80 lbs from the chassis. In the case of the Gen III, reducing the engine's length would also contribute significant savings. Weight reduction of this magnitude is only possible when you're designing a car from scratch.

The planned future LT5 engine, with its even more complex valve train, would have been 205 lbs heavier than the aluminum Gen III. Thus a Corvette designed around the Gen III aluminum engine would weigh around 405 pounds less than the same car designed to use the LT5. As a result, the LT5 engine would have had to generate 55 hp more than the Gen III, simply to compensate for the heavier car. With the Gen III generating 405 net hp and the future LT5 estimated at 475 net hp, the effective power gain would have been a mere 15 horsepower. And, given an estimated $25,000 price premium for the LT5 engine, the cost of this small increment of power is astronomical.

The Corvette had reached a crossroads. We could design the C5 around the LT5 engine or we could design a smaller, lighter car that was fitted like a glove around the Gen III small block. By opting for the smaller package, we could achieve ZR-1 performance at the price of a standard Corvette. This was too important an opportunity to ignore. As we explored it further, we convinced ourselves and Chevrolet that this was the right strategy for the next generation Corvette. This, however left us with the conundrum that the far-superior Gen III might seem, to the consumer, to be low tech.

The Gen III uses computer management to control fuel and timing, providing smoothness, high power, and efficiency -- a very high-tech feature, but earlier forms of control -- such as the four-valve combustion chamber -- were what the public perceived as modern technology. We knew that the Gen III LS1 would do just fine without these older features, as they came at such a high price, in terms of size, weight, and complexity. Like the consumer, we had been accepting the notion that complexity was good. Yet, here was one case where just the opposite was occurring. The simple solution was almost as powerful, and it was smaller, lighter, cheaper, and more fuel-efficient. Whether it was considered high-tech or not, the Gen III was the better engine. So, in the end, the only logical choice was to back the Gen III small block as the Corvette's engine of the future -- even if its roots dated back almost 50 years."


Sounds "almost" convincing :) but the only part I buy is that the GenIII was smaller and lighter. The rest of it, IMO, is simply an exercise in putting lipstick on the pig, and justifying a decision with benefit of hindsight.

"The General" went through a period in the 90's where their corporate arrogance was simply astounding; their attitude was that if they didn't invent it, then it simply wasn't any good. This was the beginning of the end for GM. This engine was designed by Lotus, not Chevy's engineers (strike 1), it was built by Mercury, not GM (strike 2), and the cost was probably over double what the GenIII (LSx) would cost to build in house (strike 3). Add to that the hand wringing bean counters who were probably moaning about what a complicated engine it was for the dealers to work on, and the potential for "in warranty" repairs, etc. and it's not surprising that Chevy bailed in favor of the GenIII, a "new" engine, but still based on the technology that has served them well for the last 50 years.
 
I coveted the 405hp ZR1 for many years. The wide rear stance and that super trick (for the time) engine.

While I understand that many find the LSx series engines "old school"... IMO they are and outstanding real world engine with the LS3 making nearly 440hp and the LS7 rated 505hp. Both of these examples are under the new rating system that started in 2006. Using the Lexus LS430 as an example in 2005 it was rated at 290hp and with NO power changes but with the new rating system it was rated at 278hp in 2006. I am not certain if this "ratio" would apply to all engines but would indicate the LS3 is more like 455hp and the LS7 is more like 527hp (which make sense with stock dynojet numbers of 450rwhp).

With such low production numbers and very limited aftermarket support the expense of building and maintaining the ZR1s LT-5 engine would be VERY high. With the breathing potential it would seem reasonable to build a 700hp version.

Some images:

390224_224.jpg


lt5display.jpg


lt5.gif
 
John, of course I respect you & your opinions, and I know I'm in the minority when it comes to my personal opinion of Detroit's motors like the LS5 & LS7.

I just believe Detroit are continually losing ground to the Germans, Japanese, and Koreans by following this direction.
 
The LT5 is a sweet motor, the new Ford Coyote 5 lt quad cam 32 looks a nice motor too. The Coyote will get the Eaton TVS 1900 supercharger treatment here in Australia by FPV, I smell an easy 400kw from a 5lt supercharged engine.

http://smh.drive.com.au/motor-news/fords-new-coyote-v8-set-to-bite-20091230-lj66.html

http://www.caradvice.com.au/32633/2010-fpv-gt-supercharged-v8-coyote-spied/

The LSx engines are hard to beat $ per hp but I agree they are quite un exciting and ugly when you pull the plastic off.
 
you guy forget about the cadillac northstar motors there over head cams and 32 valve motors and put out a lot of power when built right about 750hp
 
I saw the thread title and was going to say "Chevy" has nothing to do with it. But I see it was explained that GM outsourced the engine. I agree, it is a beast of an engine, and isn't even wound up tight.

I liked that car, and still do. You know what is funny, is the ads from GM back then for the car saying, "Turbo this, supercharge that" in a mocking fashion.
 


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