My C3 with 3.08 axle and 27" tall tyres makes max dyno'd torque at 3850 rpm (102 mph) and max HP at 5850 (155 mph) maxing-out at a currently rev limited (and possibly lifter limited) 6200 rpm - this equates to 165 mph - Now this is hypothetic, but if I had the nerve to 'drive through' that sound barrier like front end 'floaty feeling' at 115/120 mph are we saying that an early C3 with no aerodynamic aids or dropped front end would achieve these figures (and still live?)

 

71 Stock supsension, stock chin spoiler, 4-speed, 3.36 rear, 410HP (not stock), went a bit over 130, steering getting a little light, wind noise was loud, side pipes were screaming, no idea of RPM, maybe a little more room to go, but then..... the driver side headlight popped up and scred the crap out of me.

 

My last vette was an '80 I was attempting to turn into a 200 mph street car, 163 was as close as I got (verified by high school buddy @ the sherrif's dept.). I had a 375 hp crate from GM, TH-350, 3.08 rear gearing, and 275/50R15's. What I did learn is how wind resistance becomes a major factor after 140 mph or so... Takes serious power to push after that.

I figured with the car I had, I needed at least 500 hp to push it faster. With most of that power right at the top of the rpm range.

 

I think everyone would like to know what it takes to go 163 mph.
I doubt that you just dropped in a 375 hp crate motor in a stk bodied car? Can you please comment on each mod or stage of improvement? I'm sure we can benifit from your R & D. TIA

R

 

I've been thinking about this quite a bit. Now that I have an even bigger cam, my drivers side headlamp pops up at only around 130mph. The big cam, lack of air reservoir, and I think the splitter I installed attached to my Pace Car spoiler, all works together to force that headlight up. After looking over the system, the vacuum has to travel from the intake manifold, to the dash, then out to the headlights. If that vacuum is interupted or reduced significantly, like after a wide open blast for 13.02 seconds, the pop ups pop up. Maybe I need to replace the air reservoir, but hopefully with something that doesn't weigh 55lbs. I think the 90-82s have a coffee can type reservoir. I just don't know where I would mount it, and if this would even solve the problem. Many here have their headlights pop up and they still have their original battering ram reservoir.
Bee Jay

 

Long tube headers, a tri-power carb set-up, and exhaust cut-outs were the only real tricks I had going at that point. the carbs were all rodchesters I picked up at my local salvage yard. Summit Racing sold the kit that converted 2 of them to act like secondaries, they were dirt cheap too.

The origional 3:73 gearing was way too tall, but I could rev my 350 past 6,500 rpm at the top with those. When I switched to the 3:08, my set-up seamed to be too weak. Could barely pass 5,600. In 1st and 2nd gear, that motor would start having bad valve float issues around 7,200. Never dynoed it, but with the way it behaved I think it reached max power around 6,500 anyway.

If I still had it, the next couple of tricks I was going to try involved a front bumper change. I read that frontal surface area was a big place for improvement. Suspension was still tight at this speed, all I ever did was upgrade to urethane bushings. The wind noise through the T-Top was terrible, wanted to fix that too.

Hope this helps

 

I took it as a warning, and solved the issue by keeping it under 130. Hasn't happened since.

 

I got involved a little bit with this topic, long time ago, maybe even posted in this thread on it, I know I did post about it, but WHERE, I dunno....anyway....do not believe your tach and speedo, especially that speedo, it starts lying like a **** above 90 mph....I believe GARMIN, and not some tire/ratio/gearing/rpm calculator either....
I know my '75-77 stock electronic tach is good for 300 rpm OVER starting at ~2500 rpm and stays OVER by the same 300 rpm until 6000....
but it's dead on at 600-2000 rpm....dunno why, just is.....

I can also say the front end lift is spoken to be from under the hood, not above the engine, where one would assume, but from that ~16" of overhand in front of the RADIATOR support...where the a/c and Rad are blocking flow, that is the uplift/pressure area, NOT under the engine area...prove that easy, just take off the fasteners on the stock hood latch, go for a drive, the hood lays flat....no pressure there...prove it if you have a BB bulge/scoop, and some yarn on the opening....

very seldom get much room anymore...hard to do these tests....
that and finding that speedo is saying 100 mph and only doing 94, why it drops off like that, I dunno, but I think it's maybe by design....
at 80, reality is 78, that's acceptable....anything slower and it's dead nutz on....WHICH, BTW, is NOT what they claim on the calculators....

so go figger...

I beleive GARMIN, all the rest is instrumentation errors, and

 

well my tach is off but from what i've calculated, in my 77 4speed i'm at around 34-3600 cruising highway at 80, and by the time i was about to hit redline, gps told my i was at 99.8. PATHETIC! I'm going to get an aftermarket tach so i can be sure of the rpm 100%.

 

My question on the subject is aerodynamics. The body/chassis design allows for several pockets for lift. Has anyone experimented with modifying the undercarriage to reduce lift and drag?

 

All I can say is that you need horsepower + to get to 200mph and alot of areo for stabilization. I've had my 73 to 130 on a few "spirited" days, 0-100 happens real quick and things start to get hairy on the front end even with alot of suspension work done, the aero is the big thing I found, you probably need some added spoilers, dams, and some underside pans...

 

okay.. who really cares, I like just cruising the town and people looking at the car.. why run the car to 100 plus and let something break or the front get loose... nice to hit the throttle once in awhile but really just like to run around town with the t=tops off.. top speed I really could care less... runs fine at 35..75... maybe 80 on highway.. to me thats what matters.....

 

There's obviously drag inducing impingements under there, but the first order of business in countering lift is to reduce the amount of air that gets beneath the car in the first place so as to improve relative pressure differentials in favor of those above the car. An area of primary concern is below the engine compartment, which has been discussed in a number of threads, including the one below (nevermind the chit chat). IMCO, I'd take care of the above and think about a decent splitter and diffuser before spending effort on a full belly pan and airfoil profiled suspension components, as far as aero goes...

http://forums.corvetteforum.com/c3-t...ics-et-al.html

In theory (given Cd and frontal area), a properly set up late C3 ('78-79 w/dam and spoilers or '80-82) should "only" need ~650 HP to punch 200, but the real catch is that you'd better have addressed those pressure differentials if you want to stay earthbound.


mikecc, excuse me for pointing this out, but I'd think this thread is enough evidence, in and of itself, to prove that a good number of us are quite interested in this topic. Cruising at 80 MPH () doesn't happen to do it for all of us.

 

With a 3.08 rear end and tires 27" tall ( standard size for our C3's ) at 7000 RPM my tire speed was 186 mph on a chassis dyno so you need a shorter (taller ?) gear like a 2.73 or something like that and mucho HP to hit 200mph

 

I hit 140 without the chin spoiler, still tight at that speed. It still had plenty of power left, and that was without the blower.

The car is going to be drag limited for sure.

And take note, I don't have the spoiler but my car is pretty damn low. If you don't have solid suspension and low pro tires, don't do it.

 

I calculated once, with the 6 speed and a 3.70 I'm gear limited to like 270mph.

 

When I had my hood proped open for the LM2 cable, when I was tuning it, I hit about 100mph and the hood lifted because there was so much wind coming up the engine bay.


I really wish there was a way to lower the bodies on these cars. By control arm is already about an inch below the frame pocket. And I've already had the car stock on the frame rails.

I would love to put like a 4" cowl on to make room for the motor and drop the body like 4". I want that nose pactically sitting on the ground. But then you'd also have to move the trans tunnel up. And I'm sure there are things I'm forgetting.

 

A lot of people think these cars shouldn't go above 80, because of how their cars are setup. With 60 profile tires and stock suspension, I don't even think a C3 is safe at 80mph.

 

okay... I see people are interested but in the big picture only a small number of owners of these vets are actually members here and MOST value them for what they are. good cruising cars.. If I wanted or cared how fast it went I would have bought a c-4/5/6 for that..I bought a c-3 for the style and the easy to work on engine. most people dont buy a c-3 to push it to 150-200mph which is stupid..PERIOD

 

besides if you read back there is a good number of people who agree with my stance