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Demise of the LT5 Engine

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vettepilot

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Thank You Rob,
Finally some hard facts vs banter. Now we have those figures, lets get some for the ZR-1 and the 02 ZO6... then we can see where each car excells. I don't think we will see an overall "winner" each has it's strong point in their respective area, eg. 0-60, 1/4 mile, top end, 0-100-0.
For those like myself who are performance car enthusiasts rather than name plate enthusiasts I wish I had one of each of the three, but unfortunately my wallet is not as enthused as I am...
From the facts that you have provided, I think the ZR-1 would have a real problem seeing tail lights when it is so far in front...lol
vettepilot
 

Rob

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90 Corvette ZR-1

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Im not a fan of mag #'s. I tend to quote #'s that I know. I have friends that have stock and near stock GN's and T-Types run low 14's high 13's. 14.1, 13.85. I have run a 12.85 in my stock (ohhhh I put in a K&N thats a huge performance gain) 90 ZR-1. I launched @ 2400 shifted @ the up shift light and help on tight. am I saying that a ZR-1 will never loose to a turbo buick HELL NO. I know guys that would embarras me so bad id feel like a ricer racing a top fuel car. But they are modded to hell and I hope they would spank the **** outa me. But right now Im talking stock vs stock. 12.85 beats 13.85 how hard is this to get, its kinda like golf lowest # wins.

Frank I don't know what your problem is here buddy, we both drive Vettes, **** we both drive ZR-1's. I have no beef with you yet you seem to have one with me. Fine if you want to have one fine, cool, knock yourself out.

PS. Id love to park a TB in my garage.

on edit: Could we please get this back on track?
 
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My whole point is the 'real world' is much different... One of the corvette mags did a ZR1 vs Z06 shootout... the pro driver had faster times in the Z06, the owners ran and teh ZR1 came out on top...
This is why I don't like looking at test numbers... I can't find anything that shows me that a L98 automatic car will smoke an LT1 6 speed car off the line... so much so that it takes most of the quarter mile to catch up... this same L98, and a couple others I have seen, take ZR1's, C5's, you name it, off the line... These L98 cars are stock or very close to it... no major engine work, no nitros, no superchargers, no gear changes... exhaust, basic air intake mods, and the most I have seen is roller rockers.... a car with that little HP getting everyone and their brother off the line??? it isn't in the 'numbers' that the car mags have... it is the real world, the one that I live in... I can drive my car pretty well... some of my car buddies can drive their cars exceptionally well... We go by our experiences at the track, testing and tuning... Our knowledge of speed and cars goes by what we have seen, what we have tried... We are all there to help each other out... we all know where each of our cars excel in the real world... I'll see if I can dig up some timeslips to post (i just moved, it will take awhile)... but timeslips don't show how the run was (competitor or you missed shift?, not tuned right?, temperature of the run? track conditions?) Numbers are great, the real world is better
 

Edmond

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Vettelt193,

I see what you're saying about the numbers game vs. the real world factor. It's a thing that football people talk about quite often. Announcers would comment, "Yeah, he has weight room strength, but not real world strength."

Bruce Lee also talked about "real world" strength a lot.

What you're saying is that numbers don't always tell the whole story. There are so many factors that can affect the outcome of a showdown...
 

BigRed

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Here Corvette is coming in around 85 000$ to buy. Now thats fine and dandy but Mustang Cobra comes in at 40 000$. Now Im a Vetter no question, but IMHO GM had better justify the over double price tag with more than...well its a Vette!.

I don't mind Vette being 85 000 or if it go's over 100 000 so what but give us something for our money!. As far as im concerned a pushrod V8 in these price ranges is'nt going to cut it for long!. The LT-5/ZR1 were a GREAT example of that. With a 40 000$ Option over a normal Corvette people didn't mind paying the extra coin for the ULTIMATE Corvette!

Im just saying Cobra's are challenging Z06 with the same technology and for half the price! Something has to change over at GM's tech department as far as Im concerned. And with the new Bullet next year mabe it might just take the Z06 who knows!

(In the end we win in the slalom always and forever! LOL)
 

Edmond

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BigRed said:
Im just saying Cobra's are challenging Z06 with the same technology and for half the price! Something has to change over at GM's tech department as far as Im concerned. And with the new Bullet next year mabe it might just take the Z06 who knows!

(In the end we win in the slalom always and forever! LOL)

I think that GM really has that arrogant attitude that even though the Cobra is close, "It's still not on the class level of the Vette" or "You don't get the same respect from a Cobra than a Vette." I just have to say this, it doesn't matter who thinks who is better or who is more arrogant. The bottom line is production and I know that Vette owners would not want to get shown up by any Cobra that costs so much less.
 
S

sothpaw

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why does everyone love the technology so much?

It's been agreed on this thread that the LT-5 had the positive of being 4 valves per cylinder; thus, it's a high tech engine and represents Corvette well.

Forgive me if I sound like I'm whining, but why is technology for technology's sake inherently good?

I'm not sure if the consumer realizes all this "technology" is somewhat of a hoodwink--
because the more complex you make it, the less RELIABLE you make it.

In engineering school, I had a prof. who specialized in reliability engineering. Rule
number 1 is: moving parts are inherently unreliable. Eventually they will fail.

So yes, the LT-5 is more evolved, an interesting solution. But I think it's only valuable
because it had high performance for it's day. 405 hp was nothing to sneeze at in
1993. It still isn't. However, in the end, the LT-5 will be less reliable and more expensive
to maintain over it's lifetime.

The Gen III engine is simpler, inherently more reliable, therefore better in terms of maintenance
cost.

Of course, it's not really to GM's benefit to build cars that are TOO reliable--so I bet
they did pick LS1 over LT5 because LT5 was made "over there".
 

90 Corvette ZR-1

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I will assume that you have not read "Heart of the Beast" Great book I recamend it to everyone to read. The QA that went into the LT5 is unsurpassed. The testing behind it unpresidented. The LT5 will continue to run long after other conventional motors have decided they have had enough. An example of this is the World Records that the ZR-1 held.

I have personally seen cars with 200,000 miles + on them running a 13.1 on street tires (goodyears if I recall). And they continue to perform well. A stock LT5 with a open exhust and over 110,000 miles recently ran 201 or 202 mph, I can't remember right now. Yes this was radar verified.

The motor was built to be bullit proof, and from personal experience it has proven to be.
 
V

vettepilot

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I wouldn't call 4 valves per cylinder high tech, nor would I class the OHC design high tech, both are actually simple in mechanical design concept. Now I would classify variable valve timing and/or lift high tech, and computer controlled fuel and spark management high tech as well. So when we look at todays LS series engines with the fly by wire throttle, sophisticated electronic engine control, and high HP /low emmissions I think we are talking high tech dispite the "low tech" pushrod OHV design.
Seems that many think that to be "high tech" the engine has to be from Honda, BMW, Mercedes etc. A big V8 from the design studios in Detroit couldn't possibly be "high tech". JMHO on the subject, jumping into my asbestos suit now...
vettepilot
 
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I have seen very impressive things with L98's and LT1's as well... These aren't motors that fail under use or abuse either... A friend of mine finally blew his LT1... it only took a cam, heads, intake, gears, tons of track abuse, over 100k miles, oh yeah and 10 pounds of boost... all with a stock bottom end.... Are ZR1's reliable? sure, are LT1's, L98's, LS1's etc? yep, they are too... even the Vortec truck engines are super reliable... why? the process of making engines is better than it has ever been... clearances are tighter, technology has ruled! The main thing is, my LT4 is high tech because of the way it was put together... sure LT5's are reliable, but the rest of the chevy engines aren't lining up to get fixed either...

I almost bought a ZR1 with about 75k miles on it... I wasn't worried that the engine was going to blow... I was worried that when it did blow, years down the road, The only shop I would be able to find to fix it would charge me a fortune... I forsaw myself being worried about driving the car, worried about pushing it hard due to a costly repair bill if I did break something... I could blow my LT4 3 or 4 times before I reached the high cost of a single LT5 rebuild....

All the ZR1 guys in here talk about the endurance of the LT5... that is nice, but I haven't found a place for me to use that kind of endurance... I personally don't have the money, the time, or even feel like renting a track out for 24 hours to run my car....

Oh yeah, isn't the C5, with LSx technology being raced all over? C5R uses LS technology doesn't it? so do the GT cars?
 

90 Corvette ZR-1

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The motor being run by the CR5 is hardly a production engine which is what the ZR-1 set the world records with.
 
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sothpaw

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...I need to clarify

I didn't realize that LT5 had unprecidented QA, testing. That muddies the waters--it should add reliability into the engine.

Nevertheless, if the LS1/LT1/4, etc, had the same amount of QA/test, the LT5 will
be less reliable. Now, we do have a good point here about the gadgets on the LS1--
they are not a good idea from a reliability stand point either.

--The point I wanted to make transcends Corvettes. The point is: IMHO, technology should be viewed as a means to an end. If it gives you better preformance or lower cost or whatever,
that's good. But technology does have its cost: the more complex it is, the less
reliable it is. Yes, you can test it more, but then you are adding cost, your high tech solution
will cost more.

Modern American society seems to have this attitude of: "Cool, high tech, lots of features".
But the _ thing lasts a year or two, and you have to buy another one.
I disagree with this philosophy, it cost the American consumer billions.
 

90 Corvette ZR-1

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I don't know if the LTx and LSx did the same type of "see saw" test as the LT5. The LT5 was taken from peak ft/bls (where it stayed for 5 mins), the peack hp (where it stayed for 5 mins) back and forth for 200 stright hours. At anytime an LT5 could have been pulled off the line by any worker who saw something that was not up to par.
 

BigRed

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The way I see it the LT 5 would be more reliable heres why:

Each cam is 1/4 the length of a LT 1 (Just because there is more than one doesn't mean the compared weight,balance,length won't be close to the same) Now with each cam running 1/4 of the weight wouldn't that suggest easier wear on the bearings?

Pushrods- A moving part! the ZR 1 doesn't require

Rockers- A totally different system and from what Ive seen more "Active" than a pushrod engine. They are in direct contact with the cams where as the pushrod engine has 3 synapses (Cam-Rod-Rod-rocker-rocker-valve.) ((Keeping it simple Im not even mentioning lifters yet.))

The all Aluminum engine. Light weight and a great wearing alloy.

Not to mention the fact to get from 0-100 Mph we have to push our car pbly twice as hard as these ZR1's.

Thats my theory and my opinion. This is a good discussion!
 

BigRed

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BTW can you tell my next Vette will pbly be a ZR1! LOL Ive been dreaming about that car since its invention! AKA Since I was a Kid!
 

Edmond

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Re: ...I need to clarify

sothpaw said:
technology should be viewed as a means to an end

That comment just gave me flashbacks of my Philosophy instructor on Martin Heideggar.:L

But back to the subject, which seems to be LT5 vs. pushrod, I don't know... I'm sure that both setups have their advantages and disadvantages.

The reason why I brought up the potential complexity of the LT5 is because I'm reading a lot of threads where guys are looking for "certified ZR1 technicians." My interpretation of that is that the LT5 is complicated and repairs on it shouldn't be done by the home mechanic.

But 405 HP back in 1993? That is an insane number considering the LT1 back then was putting out 300 right???
 

90 Corvette ZR-1

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Lets also not forget that the LT5 was the first engine since 1974 to make more than 1 hp per cid
 

Rob

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Re: Re: ...I need to clarify

BullWinkle said:


The reason why I brought up the potential complexity of the LT5 is because I'm reading a lot of threads where guys are looking for "certified ZR1 technicians." My interpretation of that is that the LT5 is complicated and repairs on it shouldn't be done by the home mechanic.

But 405 HP back in 1993? That is an insane number considering the LT1 back then was putting out 300 right???

Yes and no. Depending upon what kind of work needs to be done to the engine, special J-tools are required. Most regular maintenance can be done with no special tools or training needed. In the almost 8 years that I've owned mine I have:

Changed the spark plugs and ignition wires, battery, oil and filter, air filter, plenum gaskets, throttle body gaskets, secondary port vacuum pump, secondary port vacuum line system, secondary port vacuum solenoid, secondary port vacuum actuators, (pulled the starter out and cleaned it and the contacts), oil pressure sensor, alternator, serpentine belt, crankcase ventilation hoses, crankcase ventilation cover gasket, MAP sensor and related vacuum hose, PCV valves and related hoses......i'm sure I'm forgetting something.

However, you get the point. NO, not all of those parts needed to be replaced....a few of them did, and most of the stuff that was under the plenum was replaced simply because it's a pain in the butt to pull the plenum off and since I was under there, I figured, what the hell.

I'm not a mechanic....about 90% of what I know, I have taught myself through the use of the 1990 Corvette Service Manual.

Why do I prefer to seek out a ZR-1 Certified mechanic if I do take my Vette to a dealer - I do so in the hope that this mechanic is experienced enough in working on all Corvettes and has an understanding of what a Corvette owner is....as well as an appreciation for the model and won't treat it like it's just another Cavalier or Beretta coming into the shop. The LT5 motor is a much different design than a pushrod motor and the software that runs the car is much different than that of a pushrod motor so hopefully, the ZR-1 certified mechanic will have a better chance at possibly diagnosing and repairing the problem rather than throwing parts at it hoping to get lucky.

I have heard of too many horror stories happening to ZR-1s at the dealership level. I'm not saying that you should not take your ZR-1 to a dealer. What I am saying is to be careful and do your research first.

The LT5 motor is extremely reliable and is more complex than the standard pushrod motor, but it's not impossible to maintain and fix.
 
W

WaR_ZR-1

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Too early a death....

When GM told Lotus/MerCruiser to stop Lotus engineers were working on a more advanced LT5 engine with Variable Valve Timing like that seen today in the Porsche 911 Turbo. [source: personal conversation with Lotus engineers at NCM at the 2000 Gathering] The advanced electronics seen on LS1/6 engines could easily have found their way into the LT5 engine. The complexity of the engine seems something of a joke as a demonstration of the engine in 1989 had 2 engineers standing on stage describing the engine as they hand assembled it, running the engine at the end of the presentation to incredulous applause.

Face it, the LS1/6 are cheaper, easier for GM to build and far more usefull than the LT5. The LS1 finds it's way into trucks, coupes and corvettes. The LT5 was production only for the ZR-1 option. Now if the LT5 had seen it's way into Camaro/Firebird and the truck line GM may have sung a different song.

Reved my car a week ago at a car show to get some folks to move out of my way, the old hand yelled at me, "Your gonna warp your rods doing that!" Didn't have the heart to yell back that I don't have any.
:CAC
 

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