Tom400CFI

Already asked and aswered in this thread:
B/c "GM" and the Corvette already hold that record.

Folks, it's not like GM would get "bad PR" if they couldn't break the record -they don't HAVE to anounce to the world that they tried it and failed. It's been stated and it's known that GM never attempted this record in the first place!! It was a private effort. The fact is, no private effort has stepped up w/a Z06 (or any other brand of STOCK car) to break the record. "GM" never did attempt to break this record, and I'm sure they never will!

As for "average speeds" at Le Mans, Indeed they may be lower, but RPM's for 24 hours are not, and RPM is what fatigues parts...especially valve springs. Obviously the LS7 and the C6R engines ahve different components, but the comparison w/the C6R was made to point out that push rod, two valve engines certainly CAN sustain high RPM for 24 hours. BTW, The ZR1 engine WAS available in boats for a short time. No demand though, because it didn't have enough low RPM torque.

The fact is, the Z06 has enough torque that it could run 24 hours at over 175 in 6th gear, which equates to about 4000 RPM. 4000 RPM for 24 hours would be a walk in the park for a current Z06/LS7.

Peaven

Fair enough, but your earlier post stated: I have to respectfully disagree about the base c6. Any stock LSx engine less than an LS7 won't cut it, IMO. Sure I'm speculating that a base c6 wouldn't be able to do it, just as you're speculating that it probably could, and that it'd be easy for the c6Z. Until either does however, it's just.....speculation.

glass slipper

While it wasn't GM specifically that attempted the record, it was their idea and they heavily fiananced it. Jim Minneker (Corvette powertrain manager at the time) had always been interested in the 24 hour endurance record (being an endurance racer himself) and had researched it in '88-'89. He set the 24 hour test as a criteria for the ZR1 during its' development so knew the ZR1 was capable. GM provided the car that was used for the 24 hour test (it had the roll cage/safety equipment/et al already there) and a stock production engine in a crate from their Milfred Proving Grounds. Delco Moraine helped with wheel bearings. Jim Minneker and Scott Allman (another Corvette engineer) were drivers. Ralph Kramer from Chevrolet public relations provided invaluable help to Tommy Morrison. Yes, there were a lot of sponsers to finance the actual attempt with GM being one of them. Yes, it was a "private" effort. But no way in hell could you ever say GM never "attempted" to break the record. GM/Ralph Kramer was the one to fire off a press release to the media announcing the record breaking run. Chevrolet ran advertisements proclaiming "In 24 hours, we did what nobody could do for 50 years." BTW, every bit of this info came from the book "Heart of the Beast" and is documented if you care to verify it. Also, GM wouldn't have to announce to the world that they failed to break the record with the C6Z...there would be plenty of others that would gleefully announce it for them. How do you think the "world" knows that Ford, Audi, and Mercedes Benz had failed before the ZR1???

I'm not sure what you're trying to say with your RPM statement...if you have lower speeds, you'll have lower RPMs. The cars will be slowing down for corners and upshifting accelerating off the corners. Each upshift drops the RPMs much below 6000 RPM. I'm not sure you can make a statement that the RPMs will be higher...peak RPMs are certainly higher during acceleration, but they are there very breifly and then the engine is given a "rest" during braking/cornering. I really don't think the 24 hours of Le Mans is a good comparison for a 24 hour endurance run. And like you said, the engine in the C6R is nothing like the engine in the C6Z so this is all a moot point. Check this link:
http://www.corvettels7.com/2006_LS7.pdf
Scroll down just a little and you'll see the peak HP in the C6R is at 5400 RPM vs 6300 RPM of the C6Z. I wouldn't refer to 5400 RPM as "high RPM" like you do.
And this link:
http://www.corvetteracing.com/cars/c6r/engine.shtml
And I quote: ""The 7.0-liter engine combination allows us to run relatively low rpm to maximize fuel economy and reliability while producing extremely high torque numbers that make the cars very ‘driver-friendly' on a road course," explained GM Racing engineer John Rice."
Clearly, the C6R engine ran at much lower RPMs at the 24 hours of Le Mans than the ZR1 did for the 24 hour endurance run.
A lot of people don't know the 7 liter C6R engine actually has a different bore/stroke than the 7 liter C6Z engine giving it a 425 cu in displacement vs the LS7 427 cu in displacement. (7 liters can be anything from 424.12-430.16 cu in due to rounding.)
http://www.corvetteracing.com/cars/c...ne_specs.shtml
(I know, the spec sheet lists 427 cu in for the C6R engine, but if you run the numbers, you get 425.44 cu in.)
Simply put, with the .591" valve lift of the LS7, I don't think there's any way a stock engine would make it for 24 hours without a valve spring failure. Look at the number of valve spring failures they've had with street driven C6Zs.

The ZR1 engine was mated to a boat, but the HP curve did not match the requirements for the water. It wasn't a lack of low end torque as the LT5 has as much if not more low end torque than other 350s. The problem was the wide/flat torque curve which gave high HP at high RPM. If the boat was propped with the proper pitch for the torque at the low end, there was too much pitch at the top end to reach peak HP. If it was propped for HP on the top end, the fuel efficiency suffered at the low end due to too little pitch. To my knowledge, no boats with the LT5 were ever offered for sale to the public. Do you have a link showing otherwise?

Finally, making the speed required for the 24 hour endurance run has nothing to do with torque...it's all about HP (look at top speed formulas, they have HP as a variable, not torque). A C6Z06 will never run 175 MPH in 6th gear. First, 175 MPH in 6th equates to 3767 RPM, not 4000 RPM. If you look at a dyno graph of the engine here:
http://www.corvettels7.com/2006_LS7.pdf
At 3767 RPM, the LS7 engine is making ~300 HP...there is no way the C6Z is going to do 175 MPH with 300 HP, it's simple math and aerodynamics. To average 175 MPH for 24 hours including gas stops/driver changes, you'll have to run at least 180 MPH on the track. In 5th gear in the C6Z, that equates to 5735 RPM...far from the 4000 RPM you stated and certainly no walk in the park anymore. And that's just to match what the ZR1 did...not looking so simple any more is it. That together with the fact the ZR1 set the record over 17 years ago really makes the accomplishment of the LT5/ZR1 all that more amazing. I believe when GM thinks they can up the ante, they will...the fact that they haven't says a lot.

PS I'm not saying the ZR1 is better than the C6Z or the C6Z is a bad car, just simply stating facts. It's also a fact that I lust for a C6Z (and will have one one day), there is nothing in the world better in my opinion...but I might be a little biased.

93RubyZ

Nice post Glass, just one comment though, the 24 hour endurance record isn't about horsepower, it's about durability/reliability. Simply stated, this equates to being able to withstand high stress applied over long periods of time. It's all about the total area under the stress vs. time curve. The C6 Z06 certainly has more power than the ZR-1, but again, durability is what the 24 hour endurance record is about.

Realize that the LT-5 was a $30k engine in 1990 -- that's about $46k in 2007 dollars when adjusted for inflation! GM made it a priority that the LT-5 be extremely durable. How embarrassing would it be and how much PR damage would it cause if their new $30k engine turned out to be a lemon? They had to do it and they succeeded. The manufacturing tolerances that were required in order to achieve the durability contributed to the high engine cost.

For those that don't know, the LT-5 was designed by Lotus with GM oversight and built by the MerCruiser division of Mercury Marine. GM would love nothing more than to take the record with an engine they could truly call their own. If they thought they could, there's no reason they wouldn't try.

Read The Heart of the Beast! It will enlighten those that aren't aware of just what it took to make the LT-5 what it is.

glass slipper

You are absolutely correct about durability/reliability being required to make the 24 hour run. I was trying to refer to the amount of HP required to get up to the speed required to make the run (as I showed with the dyno graph) and worded it very poorly, sorry for the confusion. I'll go back and edit to clarify.

Don't forget Mercruiser also had a hand in the design of the LT5.

indianavette

Looking back, what still gets me about the Fort Stockton adventure was the sheer audacity.

Twenty years ago, uncertainty weighed upon GM. Corvette was a bright spot but so miniscule money-wise within the GM universe that hardly anybody noticed. McLellan had okayed Doug Robinson's scheme to thrust Corvette into showroom stock racing by awarding test contracts to the likes of Guldstrand, Morrison, Rippie, Powell, Kim Baker.

The outcome: Total domination of the Escort series and a rekindling of a Mission Impossible mindset within the Corvette engineering group.

Who sez we can't whip Porsche? Who says we can't produce a ZR-1 supercar? Who says it has to have an OHV engine. And who sez we can't break a 50-year-old world open-class 24-hour speed record with a production car?

The truth is hardly anybody except for the handful of engineers directly involved thought they could do it. That the caper wasn't nipped in the bud by higher-ups at Chevy and GM is due mainly to the secrecy surrounding both the preparation and the run itself.

Tommy Morrison probably had more on the line than anybody. His budget was woeful, but the bills came anyway. He got some of his money back eventually because Chevy and other sponsors used him to market the incredible success of the run. You ask him today what would have happened had the mission failed. He'd tell you he doesn't dare think about it.

glass slipper

Excellent post, accurate reflection on the 'Vettes rise to a world class sports car with the C4, then supercar with the ZR1, and now the C6Z. So many people have no idea of the 'Vettes domination of the Showroom Stock racing series which pitted real production cars against each other and not purpose built race cars. In the last season, a 'Vette won every pole of every race, led every lap of every race, and of course won every race which resulted in the series changing its' name to Corvette Showroom Stock series for the next season.

Same with Tommy Morrison, his passion for the ZR1 was tremendous and he took a huge financial risk with the 24 hour record attempt.

4cefed

The thing about this statement that is fact..............it is a lot easier to say it could be done than actually going out and doing it.
I personally doubt a showroom Z06 could go out and do close to 200 mph for 24 hours.

Remember, you say 175mph. The record has gone up since then, with 17 years of technology that has gone up to. The bar has been raised and I don't think a production car will break the new mark. Only ONE way to find out........................DO IT!

Tom400CFI

Either way GM doesn't "need" to break a record that they already hold w/the "Corvette" name. The record may have been broken, but not by a stock car.


Exactly MY point. Enough TORQUE to run the car at the desired speed, at a lower engine RPM. It generates enough force, at ABOUT 4000 RPM (4500 actually, thanks to the pdf graph that you posted) to generate the hp required.

I have, and statistically, it's not that many. Shall we whip out statistics of ZR1 engine reliability issues? There were many, unfortunatly, and all it takes is one small problem to end a run like that.

I don't have a link, but I do have the magazine that did a "ZR1 shoot out" comparing a 'Vette to a ZR1 powered Donzi. First off, the above paragraph really dosn't make any sense. At least, not the way that you articulated it. I've owned, tuned, and proped boats for 24 years, and had boats that ran over 90 mph, and had 4 different props for various duties. So I know about propping and torque/power curves.
1. All boaters WANT the widest, flatest torque curve they can get. It's necessary, since there are no gears to "help" the engine get into it's power band.
2. This makes zero sense. Are you implying that the engine had TOO MUCH torque at low RPM?? Nonsense! In a boat, you simply prop for peak RPM @ peak rpm-rated hp, end of story. If, after that, if the engine has "too much low end torque", it will simply accerate to a higher RPM, more quickly! A good thing! But that's not what happens w/the ZR1 engine in a boat. What REALLY happens is that when you prop to achieve the propper peak RPM, the engine struggles to get the boat up on plane. Additionally, no one who buys a "Go fast" boat gives a rats *** abotu fuel economy suffering on teh low end. (?) Or fuel economy anywhere. Boats like that are all about show, speed and panache. If the ZR1 engine could plane heavy deep vee hulls quickly, it would have sold. FYI, I also visited Mercury Racing divison's facility back in the early '90's . I asked about when the ZR1 would be showing up in boats and they said the same thing; not enough low RPM torque.

Again, you're showing your confusion about tq and hp. HP is a function of torque Yes, you need x amount of hp to push though the wind at 175 mph. If you're going 175, and your in 6th gear, then your RPM is known. The unknown variable at that point is force (torque) available to push the resistance at that RPM. I was saying there is enough torque (and hp) available in the Z06 to do that at ABOUT 4000 RPM (but I was off by 500 RPM, read below)...

I said ABOUT 4000 RPM, as I didn't do all the math, just enough to get close, and I did.

You are right about this part. Although the C6Z is slightly more aerodynamic than the ZR1, it does definitely need ABOUT 400 hp to match or beat the record breaking speed. Still, give the Z06 the same concessions that the ZR1 were given; lowered, no mirrors, different axle ratio, and looking at the same graph you can see that the Z06 is making 400+ hp at just under 4500 RPM. Gear it to run ABOUT 180 at 4500 RPM, and now you have the low RPM's that I'm talking about which equals valve train reliability, and as said in your quote above, better fuel economy too so less gas stops, and a lower top speed needed to beat the record.

I've addressed this above w/rear gear swaps, and the fact that I never said anythign about 5th gear. You did. Put some gear in the C6Z, run it at ABOUT 4500 RPM, and give it the same 'mods' the ZR1 got (while still calling stock), and yes, it would be relatively easy. Let's get real here. The ZR1 that broke the record was far from a "showroom stock" car. I mean, it WAS very stock, but let's not fool ourselves into thinking that you could have randomly picked any ZR1 from a dealer, slapped it on the track and made that run. It wouldn't do it! That particular car was lightly modded, to optimize it for that duty, and it was gone over w/a fine tooth comb, mechanically before the run. And a current car would need the same concessions. CERTAINLY not impossible, though, as some on here have ignorantly stated...and that type statement was what my original point was adressing.

I agree. It was amazing. But the folks that are flatly stating that a current Z06 "can't even do that" are up in the night, and that type statement was what my original point was addressing.

I feel the same way. And even though I own a muff's-only C6 that regularly smokes ZR1's at our local drag strip, I stilll lust over the ZR1 and want one some day. The car is FBA, no doubt about it. BUT as bad assed as it is, the folks that are flatly stating that a current Z06 "can't even do that" are up in the night, and that type statement was what my original point was addressing. To say that the current car couldn't do it b/c it has two valves and high lift cam, is foolish. That type statement was what my original point was addressing.

Aurora40

You must live in some magical land if you have ZR-1s regularly showing up at the local drag strip.
You sure took the long way 'round to get there...

While the records the ZR-1 set 16 years ago are impressive, they really pale in comparison to your positing of generalities about boats, endurance racing, Z06's, and torque.

USAFPILOT

What would be cool is if someone took a Z with 100,000 miles on it or more out there and did it again. They dont have to necessarily reset the record but just match it. That would be

glass slipper

They're talking about torque to accelerate off a corner at lower speeds in lower gears, not top end...apples and oranges. Again, it's not about torque when it comes to top speed, please look at formulas for calculating terminal velocity, the predominate terms are HP and aerodynamic drag. Check here: http://home.earthlink.net/~jonaa/topspeed.html
So which is it, 4000 or 4500 RPM...I can tell you for a fact it's not 4000 RPM.

We've seen quite a few LS7 valve spring failures just on this forum and we represent a small sampling of the total C6Z production. In my opinion, one valve spring failure is too many since it takes the whole engine with it. And yes, please do "whip out" your statistics on the reliability of the LT5. I can't wait to see the "many" reliability issues...the LT5 is recognized as a very reliable engine that can be beat on regularly and still perform to 200,000 miles. Maybe you forget the LSx engine blocks took a lot from the LT5 block architecture.

I have that same magazine and that is the only boat I know of that had the LT5 in it...there was never a production boat that offered the LT5 engine, Mercruiser never created a marinized version so please stop stating the LT5 is a boat motor as that is totally inaccurate.

You may have owned and propped a 90 MPH boat, but that doesn't mean you understand the relationship between the power curve and HP required to overcome hydrodynamic drag or the desired torque curve for a boat. Boaters don't want wide flat torque curves, cars do. Boaters want high torque at low RPM to get them up on plane and then HP peaking around 5000 RPM so they don't beat the hell out of the engines when running at top speed. The LT5 peaked at 6000 RPM. I know very well how to prop a boat, I've had a 34' Scarab for 17 years now with different engine combos. It started with twin 454 Magnums/Bravo drives, then I went to 467s with cams and dry headers (500 HP each) with drives modded by The Bravo Shop and nose cones, and I'm presently building 600 HP solid roller cam 467s on the same drives. I think I know a thing or two about go-fast boats and HP/propping.

The prop for the LT5 would have less pitch in order for the engine to reach 6000 RPM. Then at the lower cruise RPMs, the engine would be turning more RPMs than it needed to making it inefficient at cruise speeds which is where most boats spend their time...even go-fast boats. And boaters do care about fuel economy. I have a 200 gallon tank that takes over $600 to fill. If I can increase my cruising 1.7 MPG to 1.9 MPG, I save $60 on every tank of gas...that's a weekend of racing in my ZR1 to me. The LT5 certainly has enough low RPM torque, like i said it has more than any other 350 cu in production engine. The real problem with the LT5 in a boat was cost. While the LT5 would certainly power a heavy go-fast like my Scarab, the 454 Magnum made about the same HP and was about the same weight but cost significantly less. Also, with the LT5 being all aluminum, it would have required a closed loop cooling system adding to the cost of marinizing an already very expensive engine. I'm not calling you a liar, but I doubt very much anybody at Mercruiser but the janitor would have said the LT5 didn't have enough low RPM torque. The dyno graphs don't back up that assertion. Next time you're in Jacksonville, FL, I'll take you for a ride in my ZR1 and let you experience its' low RPM torque first hand...I can drive around all day in 6th gear at 25 MPH at ~500 RPM and step into it at any time to smoothly accelerate...no stumbling or anything. Let's see the LS7 do that.

Torque will not be unknown...if you know the RPM and have the dyno graph (which we do), you know the torque. There is simply not enough HP at 4000 RPM to do 175 MPH in the Z06. I'm not the one confused about HP and torque, you are. I'm a mechanical engineer that works with HP every day in my job, I fully understand the mathematical relationship between the two more so than you as well as what each term represents. Torque is a force that can determine how fast you accelerate...a=F/m. However, you can also have torque and not be moving. If I push with 100 LBs on a 5 foot bar to produce 500 LB-FT of torque but it requires 600 LB-FT to move the shaft, I'm producing a lot of force but no HP since RPM=0. So torque is just a force that means nothing without movement. Not only is HP=T*RPM/5252, it's also torque integrated wrt to time (Tdt) using calculus. HP is the rate you do work which is why HP (not torque) is used in all 1/4 mile (MPH and ET), automobile top speed, and boat top speed formulas. See here for boat top speed formulas:
http://www.go-fast.com/boat_speed_predictions.htm

The C6Z is not more aerodynamic than the ZR1, they are the same...we've had this discussion before. I agree it has the HP at 4500 RPM to run 180 MPH, but then all you'll do is match the record at best. It won't have enough HP to accelerate to any higher velocity since the HP required to go faster goes up faster than HP increases on the dyno curve as RPM goes up. Congratulations, you just matched a 17 year old record...and I believe the C6Z could easily do that.

You're right, the ZR1 that broke the record was far from stock...it had lots of safety equipment that added weight to the car plus a suitcase full of spare parts (more weight) in the back (as allowed by the FIA rules) for any incidental failures. It had a different rear end gear and special tires (again for safety, no performance gain) for the high speed run. It didn't have catalytic converters (again for safety), but the engine was "showroom stock", not "lightly modded". No ZR1 from the showroom floor would have made the record run...I agree with that. But the mods done were allowed under the FIA rules and didn't add much if any to the HP of the engine. The C6Z would certainly be allowed to be optimized IAW the rules.

Fair enough, I'll change my opinion (it is just an opinion and doesn't really matter in the overall scheme of things) and say it will be difficult for the C6Z to get the unlimited record back due to the possibility of high RPM valve spring failure. (I don't think I said "impossible", but may have implied it.) The ZR1 captured the unlimited record at the time, VW has it now...I'll settle for nothing less than recapturing the unlimited record. In spite of my opinion, I would love for the C6Z to get that record back and would be pulling for it as hard as anybody else. I would certainly contribute $100 to any viable effort to do so. As much as the talk here seems negative towards the C6Z, I think we're just disappointed that Chevy hasn't made an attempt and we're taunting them to prove us wrong...we want the unlimited record back under the Corvette name where it rightfully belongs. The 24 hour record is the last performance number by the ZR1/"King of the Hill" that hasn't been exceeded by any subsequent 'Vettes...it's about time the "King" passes the crown on and we all say "long live the King!!!"

Tom400CFI

RMR Drag strip in SLC. There's a guy that comes down every "club racing night" w/a '90 ZR1. He's run a best of 13.5 to my 13.02. Both those times sound terrible, but keep in mind that we're at 4400' and dealing w/a DA of over 7000' most evenings.

Tom400CFI

That reply was even longer than mine. W/pics and everything! I'll just say a couple things to keep it simple:
*I never said the ZR1 was a boat engine. I said that it wasn't because of its charateristics. (the guy at Merc wasn't the janator, BTW)
*I never attacked you specifically; I originally posted to anyone who flatly states that the Z06 can't beat the record b/c it has pushrods and high lift. That is wrong. You yourself conceeded that the ZR1 has enough hp at 4500 RPM to match the record w/the right gearing. So gear it to run 185, and turn what, 5000 RPM? That was my point, that it's obtainable, and it is.
*SORRY about doing some rough, very quick math and coming up w/the term "ABOUT4000 RPM". I should have spent a little more time to come up with 4501 RPM as the theoretical number necessary. To ME, "about" was refering to that general RPM range, as opposed to "about" 6000 RPM which is closer to where it would be turning in 5th gear.
*I agree w/you about the cruising sped RPM and fuel consumption on a boat, but disagree w/you about your propping and boating-engine theory. We'll have to just disagree here, but I didn't own and operate a boat that ran over 90 w/o understanding how it worked. I MADE it run over 90, and BTW that was at 6500 RPM. I sold that boat w/over 2000 hours on the original engine.

I agree that I too would love to see someone take a 'Vette...ANY 'Vette and reclaim the title. When the ZR1 did that back in the day, in MY mind, it gave that car massive credibility, and commanded respect. The car was the undeniable master of everything (in my mind). I still think it's one of the baddest cars of all time, and I kind of wish I had bought one instead of my C6. What I need to do is talk the '90 owner that's in our club into trading w/me for a day so I can see what it's really like....

USAFPILOT

I still think one of the modded ZR1's around here might have the formula which could take the record back. I know nothing about math, HP and TQ. I'm no engineer, but I have a hunch. The stock ZR1 was only barely beat by a 1 off prototype thing from VW. I think it would be a great comeback for the now 17 year old LT5, even if it was enhanced.

glass slipper

I got you confused with another post, you never did say the LT5 was a boat engine...my apologies.:o

It's OK, I didn't take it as attacking me. But after reading my previous post, I was strongly implying what you said and decided I didn't want to be in that group. I don't want to say it's impossible, I want somebody to try. Also, we're just having a discussion that hopefully everybody can learn new things from. And that leads to my next paragraph which is going to surprise you.

To average 185 MPH, the speeds on track would have to be 190 MPH. With the mods allowed by FIA, I think 5500 RPM with ~480 HP available would easily do it. A change to a 3.15 rear gear would just about put them there. I think if the C6 body were used along with narrower wheels/tires, even less RPM would be needed. The C6 coupe has a Cd of .28 while the C6Z has a Cd of .342 plus the Z06 is 3 inches wider making the frontal area more. It would seem like that would be allowed by the rules. With the regular C6 body, it would take a little less than 5000 RPM to have enough HP to run 190 MPH. If we could gear it to use 4th (maybe the 2.56 rear end and 2.6 inch taller tire), we could knock off another 10 HP needed to attain 190 MPH and reduce RPM even further. (4th gear has a straight through power flow...the input and output shafts are "locked" together meaning no power flows through gears which saves ~2% or ~10 HP loss through the transmission.) You know what, I have to change my opinion again and say: "Damn!!! What are we waiting for...this thing is absolutely doable!!"

I told you you'd be surprised. I think I learned something!

PS Your boat motor must have been a 2-stroke outboard if it was turning 6500 RPM. I thought we were talking about heavy, deep V-bottom go-fast boats like my Scarab. Small and big block Chevys don't like to be turned that high in a boat for extended periods. My big blocks are turning 6000 RPM on the top end which is 500 RPM more than conventional thinking. If they blow, I'll just build some 565 big blocks to get my 650 HP at a lower RPM.

Tom400CFI

Damn...we ARE on the same page!! Good post. I agree w/you about the bodies, aero, and your theory about 4th gear. That post got me very excited because it shows how seemingly achievable it could be! Someone needs to do it!!

You're also right about my boat. It was an 18' Hydrostream. Power was your garden variety Merc 200 w/ minor mods like nose cone, exhaust plate, reeds, and milled heads. The boat featured Dual steering, Gas pedal, Jack plate, trim buttons on the wheel, rigid motor mounts, and coolant water pressure gauge. The thing was pretty cool, and would run an easy and smooth 80+ w/a 26" chopper prop, and over 90 with a 26" thru-hub cleaver. Though the cleaver gave you a hair raising experience. That boat was awesome and I miss it. I "putt-putt" along now w/a Mastercraft that tops out at 41 mph.

glass slipper

I can be opinionated, but I can also be persuaded to change my mind.
The LT5 peak HP occurred at 6000 RPM and had very low lift (.390") on a small 1.54" intake valve making stress in the valvetrain very low. With the LS7 peak HP occurring at 6300 RPM and .591" lift on a big 2.2" intake valve (although it is titanium), valvetrain stress becomes a big factor. With the LT5 running close to its' peak HP RPM, I assumed the same thing for the LS7 until you challenged that thinking. Although you were on the wrong track by looking at torque, it got me looking at the numbers. Your persistence got me to running numbers and boy was I surprised!
Thanks for the discussion...and go to the Z06 section to see a thread I started challenging the Z06 guys to match my $100 contribution to a record attempt by a C6Z.

PS I saw your thread there on top speed in 6th. Can I persuade you to change to HP in top speed discussions and stop using torque??? For one last attempt, torque can be multiplied (that's what the gears are for). Torque at the wheels at 5000 RPM in 1st is significantly more than 5000 RPM in 6th...1st is 2.66:1 and 6th is .50:1 so no big surprise there. However, 5000 RPM in 1st, 2nd, 3rd, 4th, 5th, or 6th makes the same HP to the wheels (4th will be a little more due to the straight through power flow). HP can't be multiplied and that's why it's used in all the different performance formulas. Yes, you could use torque in those formulas, but then you'd have to include the RPM (rate) at which that "force" is applied. As you noted in your post, HP=T*RPM/5252...as you can see, HP already has RPM factored in making HP the preferred term in performance discussions since it's the "rate that work is done".

WydGlydJim

"Shall we whip out statistics of ZR1 engine reliability issues?"

Please do; this is the first I've heard of reliabilty issues from production engines that hold basically all the endurance records.

Tom400CFI

Awesome! Thank you for taking the time to think about what I was trying to say. Many on this forum don't. I'll check out that thread, and I'll throw $100 for that cause too! Even though I don't own a Z06, I'm totally in agreement with you about a Corvette holding that record.


Changed. Just so you know that I'm not "HP/TQ retarded", let me explain why I used the term "torque" in these two threads: I started w/175 as the ZR1's average speed (and I forgot about fuel stops). I calculated roughly the RPM a Z06 would turn in 6th at 175 and got roughly 4k. So since I "know" the RPM, and that is one of the factors in the hp formula, the other factor which I didn't know was torque. So I was wondering, does the Z06 have enough torque at RPM to do meet that goal. Well, as you stated, "torque at RPM" IS HP so that is definiltey a more simple way to word it. Changed in the "6th gear thread".