Forum: Like many, I want to make my 74 a better high speed driver.
Perhaps do a HPDE day or two?
To me the problem is matching the parts to the speed being driven.
I'm sure the road undulations at 140mph are big whoops at 160mph.
I have no interest in building a race car, I just want to be able to drive the car hard w/o crashing or breaking something. User friendly power and balanced handling are very important. I already have most of the
VB&P parts on chassis: SSs, bars, brakes and lines.

I'm trying to get my Vette solid enough to run the 135mph rally car class in the Silver State. To me that means being solid at 140+.

The question is: Can I run 140+ safely 460/330 springs? I've taken off
#100 in front and intend to reduce sprung and unsprung weight. I don't want to make the car so stiff that the Mrs. won't ride w/me. LOL
This is assuming a few choice aero aids, stock in not an issue.

I run 315 rwtq at 4K, that should be enough power to pull a .70 OD?
My engine is good to go, I want the get everything else up to speed.

Some suggestions from those that know would be nice.

TIA

R

 

0ooooooooooooooooo I like this thread.........

 

 

My '71 has done 150 and was still pulling like a train, I was racing a motorbike who was never more than 2 ft off my rear bumper! It was sooooo loud at those speeds

I have a front spoiler, lots of VBP parts, Borgeson steering, adjustable shocks, 5 speed, 17" wheels etc, the car felt pretty stable but any big bump would have been trouble, but a big bump would unsettle most cars.

I think the best thing to do is to fit a cage, even if it's a small one that has door bars going to the footwell, behind the seats and down to the chassis in the luggage area, this will stiffen up the chassis enough and is my next move. The vette chassis is too floppy and it's this IMHO that upsets the car the most as the chassis is constantly twisting as well as the suspension. And it gets worse the harder the suspension gets.

If i'd have known the chassis was as floppy as this i'd have put the cage in long ago.

Good luck

 

Wouldn't even think of it w/o cage.
I have to avoid removable rear window.
After the cage comes Recaros!

R

 

Oh yeah, some sort of cage from a safety point of view too, not just chassis stiffening

 

Springs and sways are for roll control. For straight line speed is just body rake angle and earodynamics.

I wouldn't put a dime into modding the front end with or both ends for that matter with anything short of adjustable semi/full coil overs and shocks.

As to hitting a big bump at speed. Softer springs would be more complient and follow the pavement surface where as super hard might just go air born. But the safety side of stiff springs is if you ever get sideways with sticky tires you just slide around doing 360's. Where soft would get body roll and feasably roll.

I did lazy 360's at high speed into a turn out at the track and off into the gravel traps. I just got it moving again and drove to the pits. Later in the same place a racing BMW M-3 was rolling over and then end over end

 

Maybe the question should be:
How fast can I go w/what I have?
A one pc front end is #150 lighter,
that has to help.
I can't help but think that some drop spindles
would solve a lot of problems. lol

As for some f/r rake, also mando!
I'm thinking more about a traditional Grand Touring car.
Something that is barely competent, but not optimised.

I keep thinking of orignal LT1 as a good starting point.
Keeping this a bolt on project w/minimal fabrication
is important.

Thanks George, I've been waiting for your input.

R

 

George: You and some other members have spent enough to buy a C6,
trying to make our C3s faster. LOL

I'm hoping that the forum can suggest some best bang for the buck bolt on mods.
Coil overs are not on my list!
I hate to replace perfectly good parts unless they require upgrading.

I plan to do this in stages.
Stage I is rebuilt steering box and a few repairs for now.
That should have me on the road safely.

R

 

I ment to say getting my steering box blueprinted. It would be nice to have everything pointed in the same direction before hitting the gas.
That's where the flat tq curve comes in. Just like a big dirt bike or flat track twin, it is nice to have lots of tq to pull out of corner with. I like being able to run a gear high and not have to shift coming out of corner.
Then I can concentrate on a proper line, among other things.

I used to ride 125cc MX, pre LT suspension, watercooling, or powervalves! It was a very busy bike.I'm past that now. LOL

I have learned a lot about user friendly and entry level over the years.
I'm trying to apply it now.

R

 

I've had my 74 up to 120 with a 427 big block and the stock 350 suspension so it was about an inch low. I had no problems.
I've heard early c3 get light in the front so my big block my have compensated?

My 82 I've had up to 138 and the damn head lights flipped up from the pressure. Let me tell you, it gets noisy and you feel it instantly when those headlights pop. Scared the $hit out of me

 

No amount of questions can make up for actual experience. To compete in any of the open road races you have to have credentials. So you also live not very far from one of the safer road racing tracks in America. (Thunder Hill) If I was you I would look at their schedual and figure out a play day. Hook up with one of the driving instructors and just get started.

You would have to work at it to hit something at T.H.

driving on a track will help you formulate what you need first

 

IMCO one shouldn't race in such an event without knowing beforehand (rather than speculating) pretty much how the car in question handles/reacts throughout it's performance envelope. If you plan on really pushing things and your own backside doesn't already have a good idea, you had best sneak up on balance (don't overlook aero) from the understeer end of the equation, doing so in a safe environment and listening intently to what the car needs. Sorry, but you're highly unlikely to hit the nail on the head first time out, so expect to wind up with a few redundant bits by they time you're done. (IMHO if you don't have left-overs, you're not there yet.)

As for any specific advice you might receive on springs and bars (I urge you to balance your car w/o a rear one), not all that many enthusiasts actually know how their cars handle at the very limits. Still fewer are those who can sufficiently diagnose and tune a chassis for hardcore pavement pounding. Bear in mind, many a setup that feels spectacular (or "neutral") at 7-8/10ths will ultimately oversteer at 10/10ths. The inescapable fact is, get the rear anti-roll stiffness too stiff relative to the front, and you will absolutely have an oversteering car on your hands. My $.02, offered as food for thought to anyone about to jump into deeper waters...


TSW

 

Good idea running a few HPDE's, and riding in some cars actually designed for those speeds. I run a few a year in my C6 ZO6, and can tell you, 150 mph is a rarity. Pretty stable, but can't say I'd be wanting to do that in a C3. Keep in mind, most tracks require running with the windows down, and takes a lot of power.

 

You can be or even think that you are a good street racer and you have a car to match. But the difference on the track is long sustained abuse. You will find out that your Vette brakes are are only good for a few laps and that includes the c-6's.

You will find that your tires get destroyed, you have too much front dive even with 550 pound springs, The body has way to much roll. Your rear tires don't have enough grip and oversteer is the results

 

Oh yeah, brakes, forgot to mention those, as a major biggie on the track. It's all about 140 mph down to 60, like right now on the track, and way different from street driving. Don't try ceramic pads there, unless you like crashing into things. As mentioned, go to a couple track days, and see what it's like. As for tires, I run Hoosier R6's at the track, as you'll really burn through street rubber. Way more fun too.

 

A 220MPH C3 at the Salt Flat
http://forums.corvetteforum.com/c3-t...alt-flats.html

 

rescued............back at the top........

 

Understeer tends to get less as speeds increase. For safety at very high speeds, you probably have to get it to understeer like a minivan at low speeds. That means a big fat front bar (maybe 1 1/8") and a very light rear bar (perhaps 9/16"). Mount 'em in poly to minimize any compliance. Any bigger than an 1 1/8" front bar, and you are most likely twisting the frame as much as you are loading the tires.
Stiff springs will tend to not change the ride height so much at speed, if you are experiencing lift or downforce.
Look at the Chevy Power book to see how the factory prepped the cars back in the day.
Be afraid enough to be careful. But have fun.
Good luck.