Fiberglass hood mods... crazy?

[Bill Dedman]

Right, Burntorange.

My car will be mainly on the strip; I'm not so concerned with getting rid of the heat; just the air pressure. I think it has aerodynamic issues...

 

[res1vw21]

On newer cars the have a belly pan that causes the air to be channeled out from the underside. When a car is in motion air builds up in the bay and is swirling around, what this pan does is eliminate the air from the bottom so just the air from the grill is coming in. The pan has vents towards the back so that air is forced to flow over the engine then out the back. Thats how new cars can have a smaller grill, more efficient cooling, it also adds MPG. (less drag from swirling air, same idea as a tunno cover on a truck bed) High speed salt flat cars have very smooth bottoms, and airplanes are round for a reason. It's all about less drag. I don't know if something like this would work for you but it might be a viable alternative.

 

[IgotDUST]

On newer cars the have a belly pan that causes the air to be channeled out from the underside. When a car is in motion air builds up in the bay and is swirling around, what this pan does is eliminate the air from the bottom so just the air from the grill is coming in. The pan has vents towards the back so that air is forced to flow over the engine then out the back. Thats how new cars can have a smaller grill, more efficient cooling, it also adds MPG. (less drag from swirling air, same idea as a tunno cover on a truck bed) High speed salt flat cars have very smooth bottoms, and airplanes are round for a reason. It's all about less drag. I don't know if something like this would work for you but it might be a viable alternative.

Not sure if anyone had noticed but i mentioned earlier on the use of a belly pan do drop engine bay pressures.

it would be fairly simple to make your own and you could do it without having to vent the hood.

Just make a :belly" pan for it and on the firewall side of the pan you fab up, take and put a 45 degree flap on it.

So as your driving the car,wind that would normally rush under the chassis and swirl up into the engine bay and hold the car back will now hit the belly pan avoiding the engine bay all together and instead of passing the belly pan and swinging up over it and rushing back into the engine bay anyhow, the 45 degree flap will alot the air to pass over the belly pan then hit the 45 degree flap and deflect the wind towards the ground completely avoiding the engine bay, then the only wind entering the engine bay will be that of the fan which will not cause drag because it is stationary on the vehicle as it is in motion and not a force of opposing energy to create drag.

And then the only wind to contend with that would be slowing you down and creating any drag would be what pass's though your grill, which could also be remedied.

You could pop the grill out and sheet metal behind it and build your own "ducting system" to route the air coming in through the grill to deflect under the car just before your "belly pan" you fab up and it would avoid the enine bay as well!.

And to maintain cooling, you could cut a few elongated strips in the sheet metal behind the grill to allow some air to pass through for cooling purposes.

I don't know, I don't mean to knock your idea,it is cool and I get your reasoning behind it...But I personally as well as I am sure alot of other guys don't agree with chopping a perfectly good hood when there is an alternative route that can be taken to accomplish the same goals and maintain factory styling all the while.

And even after you do make the mod, I don't think you will be looking at a hugely noticeable difference in your 1/4 et.

It would not cost a hole lot of money or time for that matter to go about it the way I had mentioned and your going to achieve the same goal.

Rather it be that you leave the undercarriage open and vent the hood...allowing pressure to build and escape....or that you go the route I mentioned and avoid the air pressure from building in the first place .

Either way you go about modding it...It will be an interesting thread none the less and will grab people attention and spark ideas in the thoughts of others and would be cool to see pictures.

Good luck


P.S. Not sure if anyone is aware of this but the tonneua cover gas mileage thing is a miyth, It has been proven that you get better gas milage with out the cover on a truck because the wind that goes over the cab of the truck then drops down inside of the bed of the truck and creates a whirl wind effect that actually once over the cab and into the bed push's the truck forward and creating less drag....with the cover on the wind came over the cab and push on the back of the truck and rolling over the tail gat and grabbing the undercarriage and pulling it backwards ...slowing it down.

Not sure if anyone was aware of that or not lol...look it up on myth busters lol

 

[Dorian]

Being that this is a drag racing car you would have to consider ground clearances under it. Not just for the minimum height required by NHRA but also that it does not trip the beams too early when you launch. A friend of mine made a belly pan for his car and he could not figure out why he kept red lighting all the time!
On the other side, a belly pan can be used with an engine diaper. Some tracks charge a racer if he drops oil all down the track, a rule I see NHRA adopting in the future.

 

[res1vw21]

Not sure if anyone had noticed but i mentioned earlier on the use of a belly pan do drop engine bay pressures.

haha I just reread the posts and yes you did.

P.S. Not sure if anyone is aware of this but the tonneua cover gas mileage thing is a miyth, It has been proven that you get better gas milage with out the cover on a truck because the wind that goes over the cab of the truck then drops down inside of the bed of the truck and creates a whirl wind effect that actually once over the cab and into the bed push's the truck forward and creating less drag....with the cover on the wind came over the cab and push on the back of the truck and rolling over the tail gat and grabbing the undercarriage and pulling it backwards ...slowing it down.

Not sure if anyone was aware of that or not lol...look it up on myth busters lol

interesting I guess that makes sense, when this happens the tail gate is up?

 

[IgotDUST]

haha I just reread the posts and yes you did.


interesting I guess that makes sense, when this happens the tail gate is up?

Ya that is with the tail gate closed.....They did a test on tail gate down to,but I can't remember what the outcome of that was, I think it was worse then tail gate up and worse then a tonnuea cover...but not 100% ,been awhile since I seen that episode

 

[Bill Dedman]

MythBusters got the least drag with the bed empty and the tailgate up.

Lowering the tailgate increased drag, but it was minimal...

I don't remember anything about the toneau cover test except that it wasn't good.... Tailgate up; no tonneau, was the best.

 

[Bill Dedman]

Being that this is a drag racing car you would have to consider ground clearances under it. Not just for the minimum height required by NHRA but also that it does not trip the beams too early when you launch. A friend of mine made a belly pan for his car and he could not figure out why he kept red lighting all the time!
On the other side, a belly pan can be used with an engine diaper. Some tracks charge a racer if he drops oil all down the track, a rule I see NHRA adopting in the future.

The light beam that starts the clocks (the one that will give you a red light, if you roll out of it too soon) would only see a belly-pan as an extension of the wheel, and couldn't red-light you because that light beam would never make it to the photocell... blocked, first by the wheel, then by the belly-pan. You can only get a red light from that light/photocell combination when the photocell "sees" the light beam before the green light comes on.

HOWEVER, the clock makers were aware that this could be a problem, so they incorporated a second light/photocell called a "GUARD BEAM," that is placed a few inches (I don't remember how far, exactly, but, it's not much...) farther down the track from the e.t. light/photocell... and IF your wheel hasn't rolled out of the e.t. light's beam when your front tire breaks the guard beam, it gives you a red light, because something is blocking the light to the e.t. photocell... and, it should not be....when your car has travelled that far.

That is probably what was happening to your friend, with the belly-pan/red lights.

My car is just a junk, Bracket car and I don't run it at NHRA tracks; they'd just laugh at it....

 

[Blownfish]

The trouble with MythBusters is they tested newer trucks, if they would have tested several different trucks including older trucks, they would have come up with totally different results. Newer trucks, ones within the last 15 or so years were designed in wind tunnels so they do better with the gate up but the older trucks like pre 87 trucks were not wind tunnel designed and some do get better results with the tail gate down, especially ones from the 70's I've had a few mid 70's Fords and they do get better fuel economy with the gate down which would lead me to believe they have less resistance but my 92 and 93 Fords I have now gets better with the gate up. My father had several mid 70's Chevies and they also did better with the gate down.

Bottom line is it depends on the truck itself.

 

[IgotDUST]

MythBusters got the least drag with the bed empty and the tailgate up.

Lowering the tailgate increased drag, but it was minimal...

I don't remember anything about the toneau cover test except that it wasn't good.... Tailgate up; no tonneau, was the best.

Sounds like I remembered the episode correctly then lol.

Like I said, it has been awhile since I last seen that one.

 

[IgotDUST]

The light beam that starts the clocks (the one that will give you a red light, if you roll out of it too soon) would only see a belly-pan as an extension of the wheel, and couldn't red-light you because that light beam would never make it to the photocell... blocked, first by the wheel, then by the belly-pan. You can only get a red light from that light/photocell combination when the photocell "sees" the light beam before the green light comes on.

HOWEVER, the clock makers were aware that this could be a problem, so they incorporated a second light/photocell called a "GUARD BEAM," that is placed a few inches (I don't remember how far, exactly, but, it's not much...) farther down the track from the e.t. light/photocell... and IF your wheel hasn't rolled out of the e.t. light's beam when your front tire breaks the guard beam, it gives you a red light, because something is blocking the light to the e.t. photocell... and, it should not be....when your car has travelled that far.

That is probably what was happening to your friend, with the belly-pan/red lights.

My car is just a junk, Bracket car and I don't run it at NHRA tracks; they'd just laugh at it....

Learn something new every day lol!!!....I never no that so much technology was wrapped up into the tree.

 

[godfatherofchry]

bill;this is just a thut: what if you take a piece of sheet metal and go from the front bumper back as far as you can go and fasten it with screws to the frame. then up on the cowl cut 1 1/2x3in. oblong holes maybe 3 and let that little bit of air vent threw the cowl vents that's already there.in front of the windshield and this i know for a fact that by putting a front spoiler on the front like the ones they sell for the dusters&darts is worth 8to10 mph.just been thinking about this scene i seen this thread the other day.

 

[Bill Dedman]

That's a possibility, for sure, but the cowl "louvers" (openings) sitsright at the base of the windshield. I'm not sure how it works, but I have read many times, that the base of the windshield is a high pressure area if the car is going very fast, and as such, air that exists there, would be trying to push its way into the holes in the cowl, and the underhood air would stay right where it was... under the hood.

Just another thought....:read2:

RE: "...I never no that so much technology was wrapped up into the tree."

It's getting more complicated, all the time. Now, there's a movement within the Stock, Super Stock, and Comp Eliminators to alter the electronics of the tree so that in a handicapped race, wherein the two cars leave the line at different times, to not show the first car's red light (if he leaves too early), until the 2nd car to leave has launched, and to compare the "lights" for both cars, in case the 2nd car to leave has a WORSE red light than the first car's light, in which case, the red light wiould come on for him.

As it stands, when the first car to leave red lights, the 2nd car never has a CHANCE to red light, since the red bulb has already come on for the first car to leave.

That deprives the 2nd car of HIS chance to red light, since the race is over when the red comes on, an unfair situation. They should BOTH be under equal jeopardy of a red light to keep the playing field level.

When the 'tree was introduced, back in 1963, the software to implement this "worse red light" system didn't exist, so they just disqualified the first car to red light, which was always the slower car. That's the way it's been for 36 years....

Now, software has been designed to allow the computer to compare the "lights" between the two cars and delay turning on the red light for the worse offender, after both cars have left the line.

I don't think anybody is using this system, yet, but I think they willl be, down the road...

 

[ta3834bbl]

Truck without cover means wet tools. lol jk

I think you should vent the area just in front of the firewall out the side of the fenders like a (pardon the french) trans am did in the 70's and 80's. Place them as low and as far to the rear as you can behind the wheel. I don't think too many people would be looking there on a 4 door car, so it wouldn't be that obvious, at least not as obvious as a hinged hood. Paint it body color and have some fun. Make sure to use ducting / tubing from the fender well to the vent or the air in the wheel well will mess this plan up.

What do you think?

 

[res1vw21]

That's a possibility, for sure, but the cowl "louvers" (openings) sitsright at the base of the windshield. I'm not sure how it works, but I have read many times, that the base of the windshield is a high pressure area if the car is going very fast, and as such, air that exists there, would be trying to push its way into the holes in the cowl, and the underhood air would stay right where it was... under the hood.

hence why cowl hood cars work

 

[IgotDUST]

That's a possibility, for sure, but the cowl "louvers" (openings) sitsright at the base of the windshield. I'm not sure how it works, but I have read many times, that the base of the windshield is a high pressure area if the car is going very fast, and as such, air that exists there, would be trying to push its way into the holes in the cowl, and the underhood air would stay right where it was... under the hood.

Just another thought....:read2:

RE: "...I never no that so much technology was wrapped up into the tree."

It's getting more complicated, all the time. Now, there's a movement within the Stock, Super Stock, and Comp Eliminators to alter the electronics of the tree so that in a handicapped race, wherein the two cars leave the line at different times, to not show the first car's red light (if he leaves too early), until the 2nd car to leave has launched, and to compare the "lights" for both cars, in case the 2nd car to leave has a WORSE red light than the first car's light, in which case, the red light wiould come on for him.

As it stands, when the first car to leave red lights, the 2nd car never has a CHANCE to red light, since the red bulb has already come on for the first car to leave.

That deprives the 2nd car of HIS chance to red light, since the race is over when the red comes on, an unfair situation. They should BOTH be under equal jeopardy of a red light to keep the playing field level.

When the 'tree was introduced, back in 1963, the software to implement this "worse red light" system didn't exist, so they just disqualified the first car to red light, which was always the slower car. That's the way it's been for 36 years....

Now, software has been designed to allow the computer to compare the "lights" between the two cars and delay turning on the red light for the worse offender, after both cars have left the line.

I don't think anybody is using this system, yet, but I think they willl be, down the road...

LOL...I really did not know that that much went into the tree lol....they better not screw with it,sounds like more trouble then good....why cant they just leave well enough alone!

 

[IgotDUST]

Truck without cover means wet tools. lol jk

I think you should vent the area just in front of the firewall out the side of the fenders like a (pardon the french) trans am did in the 70's and 80's. Place them as low and as far to the rear as you can behind the wheel. I don't think too many people would be looking there on a 4 door car, so it wouldn't be that obvious, at least not as obvious as a hinged hood. Paint it body color and have some fun. Make sure to use ducting / tubing from the fender well to the vent or the air in the wheel well will mess this plan up.

What do you think?

I actually dont think this is a half bad idea either....you could do as mentioned and put in louver venting on the sides of the fenders or you could be indiscrete about it and cut your holes at the bottom the fenders on the underside facing the ground,so that all would appear to be stock but you would still be able to exit the pressure and heat in the engine bay via the ducting from the bay,through an opening into the fender well and exiting the bottoms of the fenders.

There tons of various ways you could go about it.

Now its just a question of which way lol

 

[green1]

why do you think engine bay air is slowing you down?
Do you have a gauge in there?

 

[Guitar Jones]

hence why cowl hood cars work

DING, DING, DING, DING!!! We have a winner folks. Bill, your idea has sound properties but in practice it's not very workable. You could put a small cowl scoop on it and just leave it open, not sealed to the carb or anything and it would let hot air out when you are stationary. And that is not something to sneeze at because you can cool down a hot engine compartment much quicker when you allow the hot air to rise and escape. I noticed a big difference in my Duster when I just cut the lip off the fiberglass hood that extends all the way around the periphal edges.

 

[Bill Dedman]

I think you should vent the area just in front of the firewall out the side of the fenders like a (pardon the french) trans am did in the 70's and 80's. Place them as low and as far to the rear as you can behind the wheel. I don't think too many people would be looking there on a 4 door car, so it wouldn't be that obvious, at least not as obvious as a hinged hood. Paint it body color and have some fun. Make sure to use ducting / tubing from the fender well to the vent or the air in the wheel well will mess this plan up.

What do you think?[/quote]

I think I can move a LOT more air out of that engine compartment with sizeable (10" X 18"?) flaps on the back of the hood than I can with a couple of 4" round dryer vent hoses.

I'm not sure there's even room for those hoses, and they'd of necessity, have to have some 90-degree bends on them, which might not do the flow any good...

I'm gonna continue to work towards some hood-mounted, rectangular flaps, for now, but thanks for the idea; I might end up there, eventually...

Insofar as "at least, not as obvious as a hinged hood," just what do you think you'll see when you look at this? It will be all of the original hood contours and size; the only modification visible will be the slices that define the rectangles that will lift up in the back, and these two 1/4"-tall piano hinges, which will be painted the same color as the rest of the hood. Of course, as soon as it raises up, in the back, going down the strip, you'll be able to see that, but it's too late, then... LOL!

 

[Bill Dedman]

hence why cowl hood cars work

Take a look at my setup and tell me how a cowl induction hood is going to help me.

It won't let a significant amount of air out of the engine compartment because it is configured to pick up air from the base of the windshield; a high pressure area. It would probably end up putting more air INTO the underhood area than it would evacuating it.

It won't introduce cold air into the supercharger air intake system because that inlet is at the opposite end of the engine compartment.

Cowl indiction hoods work well for normally-aspirated cars when you seal the carb to the inlet area, so they can breathe cold air and benefit from the high pressure area where the air comes from (windshield base), but none of that applies to my car; apples and oranges.

 

[Bill Dedman]

LOL...I really did not know that that much went into the tree lol....they better not screw with it,sounds like more trouble then good....why cant they just leave well enough alone!

"they better not screw with it"

How could it be any worse than it is, now? As it is, every second car to leave the line has a free ride if the first car red lights. That car never has the CHANCE to red light.
Nobody deserves a free ride; the worse red light system will ensure that BOTH cars have an EQUAL CHANCE to red light, every time... with the lesser offense being declared the winner.

[/B]"Why can't they just leave well enouh alone?"

Because it's not "well enough." Now that they have the technology to fix this flawed system, they need to do it.
It used to be that the first car to break out lost the race... then, somebody figured out that the car that broke out the LEAST needed to be the winner.

They fixed that years ago.

It's time to fix this, now...

 

[Bill Dedman]

I actually dont think this is a half bad idea either.....

There tons of various ways you could go about it.

Now its just a question of which way lol

I am going to continue to look at all possibilities, but right now, I am leaning toward two "flaps" (made from the back part of the fiberglass hood) that would be about 18"-wide (each) and 10" lengthwise of the hood, with an 18"-long piano hinge on each flap.

They would come to rest on the horizontal surfaces of the inner fender panels and cowl, just like the original hood does. The only time they would not be closed would be when air pressure from underneath forced them open, at speeds above, say, 40 mph (my guess,) When the car slows back down, below 40, gravity would pull them closed. Limiter cords would keep them from opening more than, say, 3 inches at the back. (Hinged at the front.)

It may not help anything, but like the scumbag in Dirty Harry said, "I gots t' know....":cheers:

CLICK!!! LOL!

 

[dano]

To reduce heat, you need a vent at the leading edge of your hood past the radiator. See Mitsubishi Evolutions as an example of this. Not to be critical, but your air intake is in one of the worst spots of the car, up high and next to the radiator, I know you don't have much to work with but, a cowl would work if you were to move the inlet to the firewall, I've seen this setup before on cowl hooded Mustangs with centrifugal blowers. If your trying to lower your intake charge by lowering your under hood temps, I think you have an uphill battle you'll never win without an intercooler or methanol injection.

 

[Bill Dedman]

Bill, your idea has sound properties but in practice it's not very workable.

What part is not workable? I plan on cutting two 10" X 18" panels out of the very back of the fiberglass hood (the back of the hoof will be the back of each panel), and attaching them to the rest of the hood, where they were cut from, with two 18"-wide piano hinges. Air pressure (if there is any) will raise them in the back, at speed, and let the trapped air out, decreasing drag.
I'm not that concerned about heat, or cooling, sitting still, as this car will not see much street driving.


You could put a small cowl scoop on it and just leave it open,quote]

I am trying to keep this thing looking like a bone stock 4-door sedan... LOL!

A hood scoop of any kind KILLS the stealth... Nobody's gonna notice a low-lying piano hinge.... Methinks...