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So when does a 'Vette go airborn?

4K views 34 replies 23 participants last post by  BigRed-L72 
#1 ·
I mentioned here a while back that I've signed up for one of those 1/2 mile events where you get to run WOT on a runway. I figure this is a good place to shake down the car and ensure it's happy going WOT on a track with some sort of traction....THEN I can work on dialing in the drag strip launches.
I've been posting in a sort of "blog" with Andy Bolig (think editor of Vette magazine, Corvette Enthusiast, Auto Enthusiast and general all around car guy).
I figured it might be fun for some of you to follow along as I get this thing ready to rumble!!

So when does a 'Vette go airborn?? - Bench-Racer.com


JIM
 
#3 ·
Jim, IIRC a mid year Vette gets light in the front end at 125+ MPH

Read it an old magazine so I never pushed mine past there and it was a handful even up near 120.
 
#4 ·
I had a 73 big block car that Iran up to 135 ONCE....it wasn't very stable I put an 78 pace car spoiler on after that but never ran it that fast again so not sure if it would have helped

Brian
 
#6 ·
With the IRS and the engine cranking out high torque on a high speed run, the rear end tends to squat noticeably which, in turn, makes the front end point skyward some. That is the right attitude if you want to take off (just give it some flaps). Since the 'vette is not a plane, that sort of nose-high, squat rear is pretty undesireable. A stiffer rear leaf spring would help with it, but then the car would ride like it had no suspension at all.

I took a look at the link to that blue 67 'vette. It doesn't look like squatting is an issue, it is more like keeping the front wheels on the ground when it hooks :thumbsup:
 
#7 ·
NASCAR splitter and point the exhaust upward and rearward like a funny car - that helps keep them down AND straight.

Best of luck and I'll keep my fingers crossed for you - you have more experience driving a midyear at speed than anybody I know, so you're the man for the job, IMHO.
 
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#8 ·
Thanks guys. It's got a heck of a rear leaf spring. It's a 5 leaf "Daytona" spring with an additional main leaf.

I think having a good "rake" on it will help.

I'm not out to make any hero runs. If it ain't right I'm not too proud to get my foot out of it.

Jim.
 
#9 ·
I was surprised, I ran my Chevelle across a new freeway in the desert here in the Phx area. I ran it at 130 for almost 10 miles, it was good. it's pretty low because of old original springs, got a fat front swaybar, new but not speed rated tires., It felt good at 130, not floaty at all.

Almost scary to think, it was at about 4500, maybe a little past the Tq peak, but not near the HP peak. I think the car would run 150. Not trying it without speed rated tires.
 

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#11 ·
When I bought my Chevelle(Labor Day Weekend 1969)I was 21 and Stationed in the Upper Peninsula at KI Sawyer AFB. On the return from having gone to town, there was a long slightly curved road back to the base. Not knowing any better(unknown brand of 775-14" tires) put my foot to the floor. The speedometer only went to 120, but the needle went well past that and on more occasion than I can remember. Since it stayed buried for long after I let off the gas and took the car out of gear. I have no idea how fast I was going, but if the Speedometer stopped at 120.....its anybody's guess but it sure was fun.
 
#13 ·
Depends how the car is set up. My 1st car, a bone stock 1971 Cutlass was sketchy above 90 mph. My Beaumont, which is basically the same chassis is rock solid at 150 mph. Obviously, all testing was done on closed course for safety, never on public roads. :wink2:
 
#16 ·
You're the second person to mention the Sundowner. I had forgotten about it....but I'm into it now. It does seem there are quite a few mid year Vette's at Bonneville without a bunch of wild aero tricks.




JIM
 
#17 ·
You need to control the lifting force, here's a good example what you can do with these by designing base of the car properly.

[VIDEO] 1965 Corvette Sets World Record at 201.3 MPH in the Texas Mile - Corvette: Sales, News & Lifestyle



I've followed his exploits for some time. He spent some time working up to those speeds. I got a couple of glimpses into what he might have done underneath with belly pans etc which he said helped a lot when he got near 200 MPH. He's using the same front spoiler I'm using and says it does fine.
He doesn't use any "rake" really...in fact it squats a little...but it doesn't seem to lift much on the nose....so it all seems to work well.


The car is super cool...looks stock'ish, sounds nasty and drives everywhere...and FLIES!!






JIM
 
#18 ·
Good luck with it Jim.
 
#19 ·
Added a couple of updates lately.

So far we've installed the new upper control arms to improve caster, picked out the tires and got them balanced.

Today I've added in the installation of the Viking Performance coil over shock/spring assemblies on the front.

This stuff applies to Chevelles too!

So when does a 'Vette go airborn?? - Bench-Racer.com


JIM
 
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#23 ·
Added a few more updates. This is the Eckler's front spoiler. Not finished yet but actually fit pretty good. Not sure if I'll trim it to fit bumpers or just leave them off for this event.

JIM




 
#24 ·
I ran a '68 to 147mph (according to the stock cable driven speedo and tach
) and the car seemed to float pretty high. When slowing down, I could hear an intermittent hissing noise that slowed with the car. Inspection revealed the tire separating. This was many years ago when I was in my 20's and not the brightest bulb.
 
#25 ·
Well...tomorrow is the day! Almost there!!

Bummer #1- finally got my hands on the hardtop from my buddy...doesn't clear my rollbar! I figured anything that went under the soft top and cleared going up and down would probably work. Not so.

So....that leaves me running top down or top up and hoping it stays in one piece!

I've driven it at 160+ with the top down in the past...so not a big deal I suppose other than aerodynamics.

So....if I go top down...side windows up or down for aero??

I did add the crotch belt to complete the 5 point harness...so I'm "legal" for this event.

I pumped all the old -20* W/S fluid out of the Snow Performance water/meth tank and filled with "Boost Juice" from Snow. It's a 50/50 mix rather than 30/70 of the washer fluid (which I can't even find in TX).

Pumped out the 93 octane and filled up with VP Racing MS109 fuel.

Added a few more bolts to the spoiler to help keep it solid.

Today is double check all the tuning parameters, clean it up and load it up!


Wish me luck!

JIM
 
#31 ·
Well...tomorrow is the day! Almost there!!

Bummer #1- finally got my hands on the hardtop from my buddy...doesn't clear my rollbar! I figured anything that went under the soft top and cleared going up and down would probably work. Not so.

So....that leaves me running top down or top up and hoping it stays in one piece!

I've driven it at 160+ with the top down in the past...so not a big deal I suppose other than aerodynamics.

So....if I go top down...side windows up or down for aero??

I did add the crotch belt to complete the 5 point harness...so I'm "legal" for this event.

I pumped all the old -20* W/S fluid out of the Snow Performance water/meth tank and filled with "Boost Juice" from Snow. It's a 50/50 mix rather than 30/70 of the washer fluid (which I can't even find in TX).

Pumped out the 93 octane and filled up with VP Racing MS109 fuel.

Added a few more bolts to the spoiler to help keep it solid.

Today is double check all the tuning parameters, clean it up and load it up!


Wish me luck!

JIM
windows up ! This might not even apply to you but the Mercedes convertables and other European higher end verts use a screen type piece (made of some sort of mesh fabric) that stands up behind the rear seats and redirects the airflow to keep it out of the passenger compartment.
Now I saw this on that British TV show "5th gear" and it basically was for creature comfort at 100 MPH and above but that airflow with the top down might not even make it to the rear spoiler.
So if you're counting on the rear spoiler for downforce the top down may not be the best way.
Also the 68/69 Owens Corning L88 convertible Vettes ran with a shortened front windshield to allow more air over the rear spoiler for added downforce.
http://modelcarmasterpieces.com/ima...y formula models-reg-260-spec-199-800x600.JPG
Those guys had some tricks up their sleeve.
http://www.corvetteactioncenter.com...chevrolet-corvette-l88-champion-072012-21.jpg
I don't know if the difference between the C2 and the C3 is enough that this wouldn't even matter.
 
#30 ·
Waiting to hear the tale, unless we have to wait for magazine lead time, have fun:thumbsup:
 
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