C3 front end lift (aero) question.

enkeivette said:
Bee Jay, try putting some manly springs under your frame rails and you won't be able to lift the front so easily.

My car is stable at 140mph, don't feel any lift. Now when my car was stock, I felt lift at any speed past 80mph.

The front end of a C3 is like a big spoiler, if you drop the car low enough with enough of a rake, she'll stabilize. The bottom of your oil pan might get all scraped up like mine, but it's worth it to turn your snazzy looking muscle car into a sports car. IMO.

I installed the 550 coils, with 3/4 of a coil cut and some low profile tires. I also cut out a wide opening behind the cowl on the hood.
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That is why I went with 17" wheels in front and 18" wheels in back. I also cut a full turn of my Rancho front springs. I went thru two oil pans before I found this circle track pan. The lowest point under the car is now my headers. I'm pretty steady at 140mph, the only thing that lifts now is my headlights. My car sucked at anything performance wise when new and stock.
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Bee Jay
 
enkeivette said:
Bee Jay, try putting some manly springs under your frame rails and you won't be able to lift the front so easily.
My car is stable at 140mph, don't feel any lift. Now when my car was stock, I felt lift at any speed past 80mph.

The front end of a C3 is like a big spoiler, if you drop the car low enough with enough of a rake, she'll stabilize. The bottom of your oil pan might get all scraped up like mine, but it's worth it to turn your snazzy looking muscle car into a sports car. IMO.

I installed the 550 coils, with 3/4 of a coil cut and some low profile tires. I also cut out a wide opening behind the cowl on the hood.
Click to expand...

The springs just mask the problem. There's still the same vertical force trying to lift the body (and more importantly, reduce the downward force/weight on the tires).
The rake mod is a legitimate aero mod.
I'm not following what item/area you cut behind the cowl.
 
Sadistic said:
I put this front spoiler on from FGregg Racing.
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That is a damn good looking Vette right there.:1st:
 
It should definitely help quite a bit but even more so if the front end is lowered. I hope I can get my vette to be lower. There's way too much room for air under there.
 
Here is one of my Vipers. Not to boast but look how much lower the front end is. Racers even put a splitter on the front to further push down the front end at high speeds.

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From this angle, it doesn't appear that I can lower it that much. I definitely don't want to bash my fenders up. Without making your vette look like an oddity, the F Gregg spoiler is about the best you can do, with some lowering to help. Without an overdrive transmission, I doubt there is much top speed anyway. Before I put in the 5 speed, this vette was screaming its nuts off on the highway with a 3.73 rear. It was ridiculous. If you have an overdrive trans, it is a different story and these cars were not designed for that sort of speed, so you better do something to control the lift.
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Sadistic said:
From this angle, it doesn't appear that I can lower it that much. I definitely don't want to bash my fenders up. Without making your vette look like an oddity, the F Gregg spoiler is about the best you can do, with some lowering to help. Without an overdrive transmission, I doubt there is much top speed anyway. Before I put in the 5 speed, this vette was screaming its nuts off on the highway with a 3.73 rear. It was ridiculous. If you have an overdrive trans, it is a different story and these cars were not designed for that sort of speed, so you better do something to control the lift.
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Yes i know what you mean.Mine has a 3:55 rear,its alittle better then 3:73.I can go pretty good at top speed ,but it was too hairy at the front end.My new setup has even more hp then before,hopfully the front spoiler will help,we will see.Nice car by the way,its how mine will look in the future,i have Stans flairs already .Just need to learn a little about fiberglass body work.
 
Air has nowhere to go

I believe the lift everyone is discussing is that the slant and the size of the panel around the radiator. This panel is the one that directs all the incoming air into the radiator but as others had tested. Very little air gets to the back of the top of the hood. My C4 has ductwork to the radiator and air inlet that only draws air from the center of the bumper from underneath. I would think the true repair for this issue would be to make a duct to draw air into the radiator from a much smaller surface area of the nose of the car. Then block off air flow into the area in front of the wheels so the air doesn't get trapped and create a high pressure area in the nose. Better yet vent the air on either side of the radiator into the brakes and underhood so that air would be put to use cooling the brakes and engine compartment.
I like the Front Spoiler-splitter idea because that increases front air pressure downward. Don't forget that Grand Sports cut openings in the top of the fenders to let that air out quickly to help plant the front ends.
I think I am going to do this to my car if for no other reason to improve engine compartment and front brake temps.
 
71vettewi said:
I believe the lift everyone is discussing is that the slant and the size of the panel around the radiator. This panel is the one that directs all the incoming air into the radiator but as others had tested. Very little air gets to the back of the top of the hood. My C4 has ductwork to the radiator and air inlet that only draws air from the center of the bumper from underneath. I would think the true repair for this issue would be to make a duct to draw air into the radiator from a much smaller surface area of the nose of the car. Then block off air flow into the area in front of the wheels so the air doesn't get trapped and create a high pressure area in the nose. Better yet vent the air on either side of the radiator into the brakes and underhood so that air would be put to use cooling the brakes and engine compartment.
I like the Front Spoiler-splitter idea because that increases front air pressure downward. Don't forget that Grand Sports cut openings in the top of the fenders to let that air out quickly to help plant the front ends.
I think I am going to do this to my car if for no other reason to improve engine compartment and front brake temps.
Click to expand...

I have only a Gen2 SB, roller engine <400 hp....and so have a F body radiator to fit the OEM '72 supports...and so that rad SHOULD be enough to cool the engine, I would suppose, but yet with the front tag mounted and in FLORIDA heat on the freeway it got hot...obviously something about airflow at speed, I pulled the front tag and mounting, cured THAT aspect of the problem....finally doing Dual Spals cured other slo hot traffic aspects....

so IMO, releiving pressure in front of the rad, would lessen flow through the rad, NO?? if so...it's the same a block it in the first place, I would assume??

so the fans would turn on sooner for sure, but on a long drive would they be enough to compensate for the lack of pressure/flow directed to just the rad area??

:stirpot:
 
Should be enough

The airflow, if directed straight into the rad should produce the same if not more airflow. The issue is that a lot of area is a deadend for air and therefore really doesn't do as good a job of cooling since it causes turbulance that a directed airflow would do. If it works well on my C4 why not a C3? I live in WI so cooling is less of an issue but there must be a lot of C4 owners with 383's who don't have cooling issues. I just went though a 2 mile parade and got as high as 227 degrees which was pretty good since it was in the upper 80's today. I was on the open road 4 miles and I was 197 degrees. I think that is good. I have heard many Shark owners complain of poor under hood cooling and high heat sink. So this may help.
Just an idea
-Charlie
 
I have spent a few years workin with the air flow on my vette.It passes air through very well now.At first I was working to draw more air into the rad,and engine compartment.Due to modding(lowering)the front of the hood.
I found that it was not drawing enough air into the rad,I addressed that issue and was lifting the back of the front clip and bowing the clip at 60mph on the pins.(If I pulled the keepers on the pins it would raise @ 4" at 55 to 60mph) It was drawing in enough air but it had nowhere to escape,I added louvers and raised the cowl area of the hood to let it escape and it works very well.
No coolin problems or underhood heat.I will still be modding the side vents since I added turbos but it is working very well.

Showtime010.jpg

I know that alot of this does not apply to the stock fronts but for every action there is a reaction. Most vettes could use more air passin through,but it must be let out to be effective.The Boys at GM spent alot of time addressing this.They made a few changes through the years.(They did'nt have much room to work with.)As stock vettes go,Small changes can make a big differance.(Seals,shrouds,spoilers,ect.)As for down force of the stock front.I do remember that they had to change the front of the Mako shark II,(Prototype)for the production C-3 vette.The front fenders were too drastic and made it feel unstable at higher speeds.(I believe the tall humps were creating lift.)It's been awhile since I read it,so please don't quote me on it but Thats what I remember.
 
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Showme said:
I have spent a few years workin with the air flow on my vette.It passes air through very well now.At first I was working to draw more air into the rad,and engine compartment.Due to modding(lowering)the front of the hood.
I found that it was not drawing enough air into the rad,I addressed that issue and was lifting the back of the front clip and bowing the clip at 60mph on the pins.(If I pulled the keepers on the pins it would raise @ 4" at 55 to 60mph) It was drawing in enough air but it had nowhere to escape,I added louvers and raised the cowl area of the hood to let it escape and it works very well.
No coolin problems or underhood heat.I will still be modding the side vents since I added turbos but it is working very well.

I know that alot of this does not apply to the stock fronts but for every action there is a reaction. Most vettes could use more air passin through,but it must be let out to be effective.The Boys at GM spent alot of time addressing this.They made a few changes through the years.(They did'nt have much room to work with.)As stock vettes go,Small changes can make a big differance.(Seals,shrouds,spoilers,ect.)As for down force of the stock front.I do remember that they had to change the front of the Mako shark II,(Prototype)for the production C-3 vette.The front fenders were too drastic and made it feel unstable at higher speeds.(I believe the tall humps were creating lift.)It's been awhile since I read it,so please don't quote me on it but Thats what I remember.
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I agree. When I bought my 71 stock small block it had no catches on the hood. At hiway speed the hood would lift at the windshield about an inch at 65, and another inch by 80mph. In my mind it was as simple as more air in the front and under the bottom than could be exhausted thru the side vents or under the firewall and out the back. When designing my overall body mods I did several things (none yet tested) to counter this. First was limiting the flow under the front. I used the F Gregg spoiler, but added a flange to the lower leading edge. This flange stiffens it while reducing forward ground clearance by 3/4", but also will support a plastic sweep spoiler if needed down the road. Part of the F Gregg also feeds brake coolers, the amount of air diverted to that will be determined by radiator cooling needs after testing. The original ports in the valance can be throttled to suit then fixed. That combo should solve the control issue of how much air is directed to the engine bay. The next consideration was exhausting the air. My thought was to maximize the use of the side exhaust vents. I was never too thrilled with the looks of the eggcrates and they are heavy. Looking at the later C3's all the flow is restricted by the size of the single vent opening in the fender. It is really noticably less open than say the 68 and the 69. The easy answer was to install 69 gills, but easy was never a goal. :) I liked the look of the Motion cars, so I bought 69 fender pieces and installed the inside out. Hopefully the combination of things will reduce air pressure under the hood and lift under the car. Cowl is sealed and intake air is ram through the hood but sealed from the engine bay.

Dave


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I agree. When I bought my 71 stock small block it had no catches on the hood. At hiway speed the hood would lift at the windshield about an inch at 65, and another inch by 80mph. In my mind it was as simple as more air in the front and under the bottom than could be exhausted thru the side vents or under the firewall and out the back.

My '72 is a basically stock machine, with fixed headlights in smaller openings but basically stock location, the grill is changed but little improvement there is any, and the side gills were opened up a tad by p/owner but each opening is only 7.5"x2.5" , I would say on the small side, really.....

some time ago I did a yarn test on my hood rear opening, aftermarket BB style hood, open in rear, center of hood cut out under the bulge...and got INFLOWing air, not coming out, I layed a piece of yarn over the rear edge, it was totally still, there is no gasket seal, never was since I got it....

I still feel that any lift coming on my front end is not from the hood....EXCEPT forward of the radiator...dont ask...:flash:



When designing my overall body mods I did several things (none yet tested) to counter this. First was limiting the flow under the front. I used the F Gregg spoiler, but added a flange to the lower leading edge. This flange stiffens it while reducing forward ground clearance by 3/4", but also will support a plastic sweep spoiler if needed down the road. Part of the F Gregg also feeds brake coolers, the amount of air diverted to that will be determined by radiator cooling needs after testing. The original ports in the valance can be throttled to suit then fixed. That combo should solve the control issue of how much air is directed to the engine bay. The next consideration was exhausting the air. My thought was to maximize the use of the side exhaust vents. I was never too thrilled with the looks of the eggcrates and they are heavy. Looking at the later C3's all the flow is restricted by the size of the single vent opening in the fender. It is really noticably less open than say the 68 and the 69. The easy answer was to install 69 gills, but easy was never a goal. :) I liked the look of the Motion cars, so I bought 69 fender pieces and installed the inside out. Hopefully the combination of things will reduce air pressure under the hood and lift under the car. Cowl is sealed and intake air is ram through the hood but sealed from the engine bay.

Dave


DSC08610.jpg


Sweet ride there man....with I had your talent with glass work....I too am looking at that F Gregg spoiler, maybe this winter....


:D
 
As many of you already know, I had mine up to 185mph. After some tweaking, I hope to expand on that but I think that might be about as fast as it will go. The C3 is not exactly aerodynamic.
 
Sadistic said:
As many of you already know, I had mine up to 185mph. After some tweaking, I hope to expand on that but I think that might be about as fast as it will go. The C3 is not exactly aerodynamic.
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Dash instrumentation? or Garmin.....???

unless it's a measured mile that is totally known for accuracy of markers....I don't even trust the stopwatch....
 
mrvette said:
Sadistic said:
As many of you already know, I had mine up to 185mph. After some tweaking, I hope to expand on that but I think that might be about as fast as it will go. The C3 is not exactly aerodynamic.
Click to expand...

Dash instrumentation? or Garmin.....???

unless it's a measured mile that is totally known for accuracy of markers....I don't even trust the stopwatch....
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Dash instrumentation, further confirmed by calculation of trees passed per second. A hero like myself knows 185 like you know 20mph.
 
JPhil said:
Sadistic said:
......further confirmed by calculation of trees passed per second. A hero like myself knows 185 like you know 20mph.
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:rofl::rofl::thumbs:
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Phone poles and a picket fence......

:goodnight::bonkers::rofl:

Sorry man, I got embarrased and pissed at what I wuld have SWORN was correct via the instruments, tach and speedo , and having calibrated the tach myself, and then using those tables with the tire size/rpm/ratios and shit....and supposedly I was doing 150 mph....

then a bought a GARMIN, which is what I believe......

and NO it makes NO sense to me either....I got other fish frying now....I get to it when I do....

I STLL dying to know WTF....but have NO clue....something was rotten for sure, and so HOW?? is my Unanswered question....

:hi::bonkers::cry:
 
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