Ok i read that somewhere must not be true. Bonneville is somewhere i have not been to really want to see it sometime. Still impressed with that stude going that fast in 1960.

 

Bird...Please define your comparisons in terms that support it against other cars of the c3's day. How exactly is it a brick? Against a modern c6 with the drag worked way, way down in wind tunnels it is not as good but then there are 30 + years of engineering and testing in between.

My understanding of the c3 is that it was anything but a brick like the c2 may have been but that it's issue was so much air got funneled under the front and into the engine compartment that it caused lift to occur which raised the front end and decreased steering levels at somewhere around 125 mph depending on engine. That's far different than being a brick which to me means taking a square or rectangular box and pushing it through air at high speeds, or trying to.

What drag coefficients do you refer to that qualify the c3's as a brick against cars of its day?

I ask only to refer the discussion back to facts. If it shows that then the facts will support it. If not, then the facts won't but either way they will be facts.

Thanks for posting the facts to support the statement you proposed as factual which you can tell I do not agree with.

Lance P.

 

I'm runnin' with Gordan. I raced a Ferrari last Sunday, hit 130 twice.
No chin spoiler, as close to stock as possible rebuild on the 427/435, 370's in the back, M21 and at 130 it felt good. I was tachin' around 5700 or so...busy drivin'!
My setup doesn't seem capable of too much more...200 mph...fuggetaboutit
The need for speed is a fun thing tho!!

 

Back in '77, I took my new '77 L82, 4 speed up to 100. Did you know that the vacuum operated headlights become "sucked up" by the airflow created over the front @ about 90 MPH?

I was young a foolish back then. Now I'm just foolish...

 

My 76 unmodified aerodynamically went to 120 and I've had it over 100 several times on one straight on vir's road race track in May and nothing like that happened. There are several spings on that whole assembly and I believe some of them hold it down. Makes you wonder if someone at the St. Louis factory didn't put all the springs on your headlight assembly. Mine is vacuum operated as your 77 was but I don't know what the differences might be.

Lance P.

 

+1....

My speedo at 70 mph is really 67 mph on the GPS.... at 145 mph on the speedo, my actualy speed on GPS was 135 mph... Speedo error is not linear by any stretch after 100 mph....Its starts getting way off...

With 3.36 gears, 28" tires and a T400, it didnt have much left in it... I was at around 5800 rpms..... Engine(valve train) is good to about 6100 rpms..... I probably could have hit a true 140 mph on GPS but I was concerned about sucking the oil pan dry...... Luckily my car takes barely over 1/4 mile to get there.... Maybe 3/8 mile tops..... Its pretty quick...

The car was pretty stable up that fast but the front end floats BIG TIME.....I was a little nervous but nothing out of the ordinary.... I have had it in the upper 120's (GPS and drag strip) more times then I can count....Never an issue... I sure wouldnt want to have to make a turn going over about 70 mph though....


BTW, for those of you wondering what 130 mph looks like from inside of a C3.... here you go....(actually this was 127 mph on GPS) Nothing special and not that fast I know but....this just gives you an idea of what its like in a C3 if you havent done it...
http://www.youtube.com/watch?v=Do_XK...eature=related

 

Do you have a front spoiler? Which one?

Ralph

 

My '69 is an L46 so not even close to the MPH #s you are talking about but I think that parts might start flying off of our cars if you had the HP to get there.

 

I just have the stock little plastic chin spoiler for feeding air to the radiator.... Its the $40 one from all the repop places... see sig pic..

 

Sure yours would make those speeds. I had my '69 350/300 up to about 5,500 rpm in fourth gear when it was new. So your 350/350 ought to do at least that well, assuming the engine is healthy.

Pete

 

Actually what happens is that at large throttle openings or WOT, your engine is not making any vacuum. Once the vacuum in the air tank is depleted, the headlights go up. The vacuum is needed to keep the healights shut. That is why I plan to install an electrical headlight actuation system some day. But even with electric actuation, at certain high velocities, my Fiero's headlights would rise due to the air pressure under them.
Bee Jay

 

Your 69 ought to do more than my 76 which in theory will do 138 mph the way I have it set up with true duals and faster timing and nothing done inside the engine or the heads or intake or headers. I've had it 120 on a track and the straight just wasn't long enough as it was still pulling in fourth gear. I honestly don't know how many rpms I was running 'cause I didn't take time to look...things on a road track happen too fast so I drove in my inexperience by sound and sight and listened to the engine for shifts rather than looking at the instruments. After I made the changes above it is close to 69 but not as much net horsepower because your compression was higher. If you have a four speed and 3:36 rear end you ought to be able to do better than mine.

Lance P.

 

Bee Jay....why when mine sits and the vacuum isn't there in the tank anymore don't the headlights pop up on their own with the springs on the mechanism if what you said above is true. Are you sure it is the way you said it? I don't know but wondered whether the vacuum worked to pull it up with spring assist or the springs pulled it up alone.

Either way, there are lots of springs there!

"Actually what happens is that at large throttle openings or WOT, your engine is not making any vacuum. Once the vacuum in the air tank is depleted, the headlights go up. The vacuum is needed to keep the healights shut. That is why I plan to install an electrical headlight actuation system some day. But even with electric actuation, at certain high velocities, my Fiero's headlights would rise due to the air pressure under them.
Bee Jay "

 

Lance, the reason I used cars like Chaparrals and GT40's (or actually 'GT38.5' in the case of the MkIV) for comparison is that their straightaway speeds were fairly well known and published, and there is also available data on horsepower, weight, etc., and these cars were built and competed in the late 1960's. Strictly spoken, drag coefficient is generally quite closely related to frontal area, i.e., the lateral cross-section of a car, and you don't have to look too hard to find that the frontal area of a C3 is (while still small in comparison to MOST cars) quite large when compared to a 200+ MPH sports prototype of the late 60's. I did a little digging and found one site that listed the MkIV's Cd at ".35" and found some others showing a C3's Cd as .4-.5, so just in drag coefficient there is a difference of between 17-30%. Was I exaggerating or using a bit of hyperbole when I referred to it as a "brick"? Of course. The point that I was trying to make was that these cars had to be sold to the public, and had lots of styling cues (read: aerodynamic compromises) added to make them visually appealing to potential buyers (they do LOOK fast, don't they?) while all-out race cars that are built purely for speed generally don't have to make such concessions. As a result, speed tends to erode rather quickly in the upper regimes, even with 435 horsepower. To add some more data, the MkIV weighed 2205 lbs, the Chaparral a miniscule 1752 lbs., whereas a '69 427/435 coupe is a super-chunky 3468 lbs., the MkIV was (again) 38.5" high, the Chaparral about the same, and horsepower figures were listed at 500 for the Holley-carbureted Ford with the Weber-carbed Chaparral listed at 525. Again, I am using these figures as evidence that if a given car is aerodynamically efficient enough tremendous speeds can be achieved with relatively low horsepower ratings.
To directly answer the OP's question (since I don't have the Car and Driver, Road&Track, or Motor Trend from 1969) I used figures found at automobile-catalog.com. The GT40 and Chaparral info was gotten from 'The Racing Fords' by Hans Tanner and 'Chaparral' by Richard Falconer, respectively. They (automobile-catalog) list the top speed of a 1969 427/435 Corvette coupe at 146 mph. Personally, I don't find that all that hard to believe, so when you put that number into perspective against a sports racing car of the same era with a roughly 23% lower Cd that weighs 37% less and is capable of a top speed 33% greater it becomes quite reasonable to deduce that the weight and drag of the Corvette contribute a lot to its native lack of top speed.
As I mentioned in my original post, if you stuff enough motor into that 'brick', get rid of some of that weight, give it the kind of chassis and suspension stiffening needed to make it safe at astronomical speeds, and do some not-so immediately apparent body mods like closing up forward-facing air gaps, smoothing some jagged edges, lowering the nose, etc., you can push that brick to some very impressive speeds. But, again, to answer OP, using the almighty '69 427/435 tri-power super-vette as a yardstick? Not quite 150 MPH.
When people have as much blood, sweat, and tears invested in their transportation as many Corvette owners typically do they tend to get emotionally attached to them and therefore seem to get a little irritated when some pipsqueak jumps up and calls their beloved chariot names. Certainly not my intention to offend, and I have nothing but good will toward my C3 brethren. I knew I'd get in hot water with some of you guys when I started typing...

 

I not read all the comments in a 4+ years old thread....and much less recall any posts I made....

but I can say with certainty over my elementary tests, that there is no air pressure under the hood, on TOP of the engine, the under hood pressure is in front of the radiator, before the hinge pivot point....and that makes sense....just look at it and think for a few seconds....

then we get into those clumsy headlights...they are at BEST a air damn, or a curse as you wish to say.....when down they are in the radiator air flow, slowing and deflecting air away, sucking engine power and not cooling engine, when up it's a joke.....sucking engine power and if anything they always lift the front....

the stock vac operated lights are a stone disaster in operation, I too have had them raise at full throttle with both Carb and FI on either engine....same with the vac operated wiper door, my car being the last of them as a '72......

so to go with a modified Ecklers tray setup and reduce the opening by 50% front to back, later Camaro lights fixed forward....and eliminate all the stock grill work below, just a mimic of earlier vettes....slats running horizontally.....

my previous comments about GPS/Garmin are correct....no question...

 

Kinda sums it all up really - It seems that continuous driving, say anything over 110/115 mph is challenging - the front end lift does not make for confidence where handling & braking is concerned. As Ajrothm indicates his car takes less that 1/2 mile to get to high speed - I don't have quite as much HP (dyno'd @ 528BHP) but can report a similar experience, noticing on mine that with the 3.08 rear end, M21 and with correct diameter (but modern 40% profile) 27.2" tyres, the occasional 'excercise' trip out there (off highway of course!) has inadvertedly brought the rev limiter in at 6200 rpm in third gear at 130 mph (calc'd from rpm/tyre diameter) - yet it all seems quite stable when accelerating and braking even past this speed - its just continous high speed thats at issue for me!

 

Well...if you are going to compare race cars to stock vettes then I'd argue that you are mixing apples and oranges. The chevy powerbook clearly tells how to prep a Vette to be a race car and many were prepped that way and beyond with aero's and the rest. Duntov had the cars well up into the near 200 mph with big blocks but that is not what they marketed and sold. Some of the cars prepped for road racing were lightweighted, were aero modified, were tuned for racing with different gear boxes and rear ends and while still heavier than some you mentioned pretty much were capable of getting around a race course.

I believe the drag of the car was a factor on stock but a bigger factor was the weight. The stock vette of my vintage was 48" tall at the max I believe and weighed about 3500 #'s which in those days made it a heavy mass to accelerate up to speed. Aero drag was a factor but I think just one of many. Aero lift on the front end was just plain dangerous from 140 and up and needed work but the vast majority of Vettes sold were never designed or capable of hitting 140+ from stock. It's us guys who have pumped them up to do more than that and the discussion then starts on how to get them safe at those speeds and capable of it. More than just engine power as you've pointed out. Now, take that stock 69 in your example and convert it to a race car prepped status for a better comparison and you are not nearly as far apart as your comparison of a stock 69 vette to a non stock set of race cars. Apples and oranges though a good comparison if you want to compare stock to race cars.

What seems true to me is that everyone learned between the 60's and now. The modern 2011 ZR1 with it's low drag shapes, supercharged 638 hp I think it is, huge, wide rear and front tires, more sophisticated suspension, more highly engineered brakes, good weight distribution, dry sump oil systems, etc. are capable of something like 202 mph stock right out of the box without further mods. I'd say Chevy and Ford in their cars have learned a lot from the race course. Even the Z06 with it's 500 hp is a pretty powerful v 8 engine. Some of the Ford small v8 engines made today have rather a ton of horsepower and torque in them and are smaller blocks than Chevy pushes.

 

You just have to be a little smarter than your car

If you have a little lift at higher speed. Just add some front down angle or rake and a front air dam.

As to C-3 lights lifting. My experience has been that with HP low vacuum motors it was hard to get the lights to come up. I can remember letting off the gas and down shifting to get them to come up on the way to work every morning. I had lifting open at high speed once or twice. I attributed it to perfect conditions of high speed and a head wind where the air pressure built up in front of the radiator over came the springs ability to hold them down. The air going over the nose might also be creating a lower pressure above them. Where body rake would have an effect.

Locally we have a freeway that follows a river through a 30 mile canyon. It is actually kind of fun to drive pulling "g's" in the turns. That is more than doubling the posted 70 mph speed signs. There was a guy years ago in his new Ferrari on the same stretch of road that made the news. He was ticketed for going over 180 mph. He was just doing the same thing others of us have. Slowing down to 140-150 for the turns and the cop just got him on a straight strech. I been going through there and the crazy rice bike road racers are doing the knee drag at those speeds through the big sweeping turns.

 

Gotta disagree with a couple items. Drag coefficient is not related to frontal area. Drag coefficient is an indication the efficiency of the shape of the object. A very large aircraft can have a low coefficient of drag. Total drag is the product of Cd and frontal area. Total drag is what limits a vehicle passing through air.

Weight is only a minor issue in top speed pursuit. Theoretically weight only affects the rate of acceleration (F=mA), not the top speed. However, a heavy vehicle can have more bearing/tire friction which would limit its top speed, but for our discussion it can be ignored.

 

OK, I'm gonna try and reset this...The only reason that I used the vehicles that I did in my comparison was for comparison's sake. Yes, I did use the dreaded "F" word a few times, I know. How about this? Let's use Tom McEwen's C3 Corvette Funny Car for comparison??
After all, it IS a C3, right? IT has 6000 horsepower, weighs 1800 lbs, and does the quarter mile in 5 seconds at 280 MPH!! The vehicles used in the comparisons were not for an "apples vs. oranges" debate but rather for an "evidence+evidence=conclusion" statement. As simply as it can be put, MORE power+LESS weight+LESS drag=FASTER CAR.
I used what I believe was a representative car for the object of the comparison-a '69 427/435 coupe. Possibly the fastest C3 Corvette available for purchase to the general public at the time. If that car only goes 146 MPH as stated, it is simply because a somewhat benign set of laws make it so...too much drag, too much weight, and not enough power. True, I am arguing that drag is a big part of that problem...69427 is correct in arguing that weight is not that germaine to absolute top speed as it is to acceleration, and 435 horsepower is a LOT of power, so that kinda narrows it down to one issue...the air doesn't negotiate its way around that pretty shape quite as well as it might seem. If somebody wants to make the statement that newer Vettes are faster than C3's, you'd just be agreeing with me...beginning with the C4 those cars began spending as much time in the wind tunnel as they did in the styling studio and their drag numbers show that...along with their out-of-the-box top speeds. As I mentioned a couple days ago, a new ZR1 weighs about 3000 lbs., has 638 HP, VERY low drag numbers, goes 205 MPH, and even THAT is electronically limited. Moderate weight, very low drag, BIG horsepower=VERY high speed.
I certainly didn't post any of this to get into an "I'm right/you're wrong" catfight. Those are stupid, pointless, and a waste of time IMO. I just thought this was an interesting discussion and felt like adding a little of my own perspective. I own a C3. I really like mine, and would not intentionally say anything to criticize anybody else's car. Peace all, and oh...Merry Christmas!