commander_47

Did the original L88 hood have vents in the lower front. The area right in front of the scoop itself where water collects.

I believe there were vents to extract hot air there originally.

Could someone post a pic please of how these looked originally?

many thanks

MelWff

it had one drain hole in the center of the depression

7t2vette

They never had holes to extract hot air at the front.

Ironcross

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the only other holes are for the '427' letters on the side of the scoop...they breathe from the rear

Ironcross

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Gale Banks 80'

Yes and No, would be the answer your question. No a Car never rolled off the assembly line with it cut out. And Yes a L-88 Car going down the Mussane straight at over 200 mph most likely had it cut out. I believe that it was intended to allow more Air Flow threw the Radiator, the newest C5R and C6R's use the same thing.

MelWff

i see no cuts in the hood, look at the open hood picture

http://www.corvetteblogger.com/2009/...Le-Mans-Racer/

oldalaskaman

with a good drip tray setup, I think it would be a neat place to put a vent, I'll let you know when I install mine.

Easy Mike

At that speed, a hole in the hood would be letting air out, not bringing air in.

No stock C3 hoods extracted air. Ditto for the L-88 hood - it does not extract air.

69427

That's the point. Reducing the air trapped under the hood reduces the front end lift, increasing cornering and braking traction.

MelWff

since I think we started off talking about the 68/69 LeMans entry L88, wouldnt the side gills on the fender accomplish that, plus the pictures of the real car show no cuts in the hood.

langg

I looked at a 68/69 L-88 race car in a specialty shop in Maine a couple of years back. It had two rectangular openings in the vertical face 'inside' the front of the scoop. I would say about 1 1/2 high x 3 or 4 wide. I assumed that they were there to relieve under hood pressure based on position and shape of the scoop.

Lang

commander_47

I have also seen the same type of vents. It seems to me that the design of the hood lends itself to those vents for a reason.

I always thought they were to aid in bringing in air to the radiator and venting the hot air.

I have to question the effectiveness of the side vents. With the A/C and Charcoal filter, window washer, et al in the way it doesn't seem a lot of air is getting vented there.

I would really like to see a picture of those cut out vents in an L88 hood before I start cutting mine.

Seems to me if I have to drill a drain hole anyways, I might as well forgo that and put in something more effective.

lvrpool32

The #4 Heinz and Johnson car that ran Le Mans in '72 had the vertical area cut away.



This is not how the factory cars came.

TheSkunkWorks

Perfect timing, lvrpool32.

FWIW, several C3 racers I've seen have the radiator canted forward radically, as in the stock location this particular area opens up pretty much right on top of it. Fortunately, higher pressure air will always seek to escape to a lower pressure area, even when the path isn't necessarily pretty, so even a crude opening without baffles or ducting will function to at least some extent when adequately located. Still, I'd have a hard time recommending this particular cut to just any enthusiasts.

In and event, I'd hope that it should go without question that you don't want to extract air which bypasses the rad altogether, but given the amount of confusion which often surrounds underhood aero it's probably worth mention.


TSW

damoroso

Yup. I was going to open up my L88 hood but thankfully go to looking at where exactly the air would draw from. In FRONT of the radiator....not good. My hood is aftermarket, if memory serves, the original L-88 hoods were open at the windshield and were designed for clearance for the carb and aircleaner on big blocks and to draw cold air into the engine. And they look good too!!

Belgian1979vette

A high pressure area on a car exists in front of the nose and the windscreen. The L88 hood made use of this by having the engine draw air from the cowl area.
The L88 hood's design was originally aimed only at that + additional carb space for the high rise intake.

Since the air on top of the car moves faster than the air below the car, it in fact acts as a wing, making the car lift of the ground. All sorts of things are used to reduce this effect, under which the use of air dams, spoilers and so on, which in effect reduce the amount of air that goes under the car.

The air that enters the front of the car and goes through the rad can only go out under the car or by the side vents.

Going out on top of the car (through the hood) would mean it would disrupt the air flow there and because there is a carefull balance between the amount of air on top of the car and below it could in my opinion cause more harm to the downforce on the car than anything else. The only difference would be if you could guide this air through some spoiler that would make an extra push.

An effective system to pull air from the enginebay would be to get it all out by the side where it would effect the air on top of the car. If you look at the way the rads are mounted in an F1 and the way the air is diverted after the rads you will see this. This diverted air is then guided through the rear spoilers, giving additional downforce.

TheSkunkWorks

Actually, a body in ground effect doesn't necessarily operate like a wing in free air. If it did, then it would be very difficult to generate downforce with shapes other than an inverted wing. However, to shift lift/downforce differentials in favor of the latter it's only necessary to create an area of lower pressure beneath the body than that above. Thus, dams, splitters, dive plates, extractors, barge boards, diffusers, spoilers, wings (mounted in free air)...

That said, you don't have to look at very many racing cars designed with ground effect tunnels to notice the inverted wing concept is certainly in operation there. Problem is, those tunnels are very sensitive to ride height, as are flat bottom cars with rear diffusers to a lesser extent, which is why skirts became such a big deal in their day.

As for air extractors located in hoods, many a full bodied racing car (wherever rules allow) benefits from using them, and there are plenty of fairly well thought out aftermarket hoods with extractors and/or vents, including several for our later generation brothers. And, there are, of course, the homemade ones out there, some of which leave a lot to be desired. But, even the General is coming around to putting them on hotter Camaro and Corvette production models. No, they're not for everyone, and can backfire if they're not right, but if properly done (location is key) and for good reason (posers need not apply), I'm all for them.

FWIW, here's a fairly extreme example of extracting air thru the top of the hood which apparently worked out OK...

roscobbc

I would be interesting to measure total frontal area or various year C3's related to the relatively small frontal cross section that actually draws cooling air through to radiator - on my '68 the first thing to go was the license plate holder (that must have increased potential airflow by 25%) - I would be surprised if the cross sectional area of the fender vents is equal to the frontal area mentioned above. Result (theorical naturally) = restriction in airflow under hood/engine compartment. In reality air is exhausted at the rear underside of the hood through gaps between frame and engine/transmission - even more when headers are used and dust shields removed. Of even less significance with older cars that have lost foam around bellhousing, mud flaps over a arms, fillet pieces around radiator and shroud - but then other issues take over, like overheating

damoroso

Actually, I don't think the majority of the cooling air comes in through the frontal area on these cars, it comes in under the front of the car. That's why it's so important that the spoilers and diverters are there as designed. I've seen several posts using the old string method that shows air does in fact exit through the side vents of the fenders. What that volume of air is compared to the air entering the engine compartment is anyones guess though. Another question I always have when these (very interesting) aero converstations start is at what speeds does this all really become a factor?