Installing a NASA scoop fiberglass hood w/functional RAM air

[tony-muscle]

I was posting on another thread not started by me about locating, finding and purchasing a fiberglass hood. My intention is primarily to reduce weight but also because my stock hood is not in good shape. My intention is to move my RAM air hardware from the stock hood to the fiberglass hood so I want it to continue to be functional. I will then paint the hood to match the stock so from far away it is not noticeable. Here is a link to that thread:
https://7173mustangs.com/threads/fiberglass-nasa-hood.34850/#post-396658
I pulled the trigger on a VFN fiberglass hood (http://www.vfnfiberglass.com/71-73mustang.htm). I ordered it back in November of 2021 and it arrived about 6 months later as promised in April of 2022. I was waiting for the driving season to come to an end so I can start the installation process. This hood is very light. I can carry it on my own. In theory is about 30 lbs. I don't know how much the stock weighs but I guess close to 100 lbs. I will try to weigh both of them to get a better idea of the weight savings.

Here is the hood as received:



The hood arrived in a big box and in good shape. I picked it up at Yellow Line freight.
First, I test fitted it on the car and it looked okay, except that it was too high along the fender curvature and too short on the driver side. I also removed the hood springs (https://7173mustangs.com/threads/removing-hood-springs.41789/) using a screwdriver along the front most edge of the spring. I placed an order for a 7" 25 lbs spring so I hope it works.


I removed all the hood stops from the rear and the edges so I can start from scratch. I need to find shorter or adjustable hood stops. That allowed the hood to sit lower and better match the curvature. The shorter driver side will have to be fixed by elongating the holes in the hinge since the hood is already at the front most edge. I also had to cut a small section of my custom shock tower brace. The driver side of my brace sits higher and it was in contact with the inner hood.

Then it was to fit the RAM air plenum. As noted by member @slocody in this post (https://7173mustangs.com/threads/fiberglass-nasa-hood.34850/page-2#post-398205) the VFN hood doesn't have the depression on the driver side where the RAM air sits. I don't know why Ford designed it asymmetric because I don't see the function for this depression.



That meant using the angle grinder to cut that section to make room for the depression. I will then finish the depression with fiberglass and resin. The snorkels didn't fit right away on the hood openings which meant massaging the snorkels and the actual hood until they can slide all the way. Still even after sliding the snorkels all the way, they are about 1/2" short from the exterior opening. I will eventually use some closed-cell foam here to make sure there is a seal between the snorkel and the hood exterior.



I also drilled the hole for the hinge so it can lock onto the latch. I will eventually reinforce the hinge area with a couple steel strips for safety. I have not completely attached all the screws of the RAM air since I want to first bring it to the body shop to discuss the project for prep and painting. I also need to drill a couple of holes in the area near the windshield to fit the washer fluid nozzles. Although I never use them, I might as well transfer them since it will only require a few holes. One final thought I am having is to drill a couple holes in the lower areas of the hood to allow water to drain out just in case I have so water leaking between the RAM air snorkels and hood.

I am very pleased that the fit is not that bad - similar fit to the stock. I will be using some of my fiberglass skills during the coming weeks so I will continue to post my progress here.

 

[PoFoMoCo]

Nice job Tony, can't wait to see the progress and the final fit and finish. Let's go!

 

[Vinnie]

Looking at the gaps along the sides the hood isn't in straight which could cause the drivers side to look shorter?

Apart from this it looks pretty good. Thanks for sharing your findings with us!

 

[tony-muscle]

Looking at the gaps along the sides the hood isn't in straight which could cause the drivers side to look shorter?

Apart from this it looks pretty good. Thanks for sharing your findings with us!

Thanks. Dont use that picture too much as a guide. That was taken after the first try.

 

[mrgmhale]

Just a point of consideration re: a fiberglass hood... The 69 - 70 Shelbys have fiberglass hoods, and fiberglass front fenders. The fiberglass allowed two things to happen on those year models. First, clearly the fiberglass was lighter than the metal body parts. But, just as important, the fiberglass allowed some design changes to help make those Shelbys look "different" compared to their underlying Mustang roots. First of all, the hood on those Shelbys has a plethora of holes meant to provide some practical benefits. The forward facing center scoop is designed to bring fresh, cooler air from the outside, s opposed to having the engine breath in hotter underhood air. The left and right front holes are designed to bring in cool air into the engine compartment, whereas the rear holes are supposed to let hotter underhood air escape in order to help the cooler incoming air to flow through the engine compartment, as opposed to simply coming in and getting trapped with now way out until a certain amount of pressure was achieved. I have never done any kind of testing to see of those left and right inlets and outlets actually do any kind of good, but I am curious. A project for another day.

Okay, that is the obvious stuff re: fiberglass parts and how they work on the 69-70 Shelbys. Now I offer one other thing to consider. Fiberglass is essentially a plastic compound for all practical purposes. And, plastic at higher temperatures tends to become easy to bend. If you look at those 69-70 Shelbys, specifically at the hood, you may notice many of them have hoods that, when shut, are bowed noticeably as compared to the lines of the front fender. That comes from the hot engine compartment temperatures causing the fiberglass to become pliable, and the hood springs purring constant pressure on the hood where the result is the hood begins to bow ever so slightly. Over time the bow becomes noticeable.

I have read article where folks try to correct the hood bow on those Shelbys by taking the hood off and placing it on saw horses with concrete blocks placed on top of the hood (using blanket to protect the paint, in an effort to reverse the bow. I do not know how effective that is, but I can see were with enough weight and heat that bow might be flattened out to some degree.

We have minimized the possibility of the hood bowing by opening and raising the hood of our 69 GT500 any time the car is in the garage or at a car show, in order to eliminate the hood springs applying spring pressure on the hood. I do not know how effective or useful our effort really are, but our hood is quite a bit flatter than other 69-70 Shelby hoods I have see in person or via photographs. In your case, with the various contours, your hood may be more or less susceptible to bowing. But, I would suggest you also leave your hood up when it is parked, especially with a hot engine compartment, to prevent needless bowing. The yellow Shelby in the embedded photo has a very extreme bow to it, sadly enough. Below are some links re: what causes the bow, and some suggestions on how to correct it.


https://www.vintage-mustang.com/threads/how-do-you-fix-the-dreaded-shelby-hood-bow.1185820/
https://www.saacforum.com/index.php?topic=8811.0

 

[tony-muscle]

Just a point of consideration re: a fiberglass hood... The 69 - 70 Shelbys have fiberglass hoods, and fiberglass front fenders. The fiberglass allowed two things to happen on those year models. First, clearly the fiberglass was lighter than the metal body parts. But, just as important, the fiberglass allowed some design changes to help make those Shelbys look "different" compared to their underlying Mustang roots. First of all, the hood on those Shelbys has a plethora of holes meant to provide some practical benefits. The forward facing center scoop is designed to bring fresh, cooler air from the outside, s opposed to having the engine breath in hotter underhood air. The left and right front holes are designed to bring in cool air into the engine compartment, whereas the rear holes are supposed to let hotter underhood air escape in order to help the cooler incoming air to flow through the engine compartment, as opposed to simply coming in and getting trapped with now way out until a certain amount of pressure was achieved. I have never done any kind of testing to see of those left and right inlets and outlets actually do any kind of good, but I am curious. A project for another day.

Okay, that is the obvious stuff re: fiberglass parts and how they work on the 69-70 Shelbys. Now I offer one other thing to consider. Fiberglass is essentially a plastic compound for all practical purposes. And, plastic at higher temperatures tends to become easy to bend. If you look at those 69-70 Shelbys, specifically at the hood, you may notice many of them have hoods that, when shut, are bowed noticeably as compared to the lines of the front fender. That comes from the hot engine compartment temperatures causing the fiberglass to become pliable, and the hood springs purring constant pressure on the hood where the result is the hood begins to bow ever so slightly. Over time the bow becomes noticeable.

I have read article where folks try to correct the hood bow on those Shelbys by taking the hood off and placing it on saw horses with concrete blocks placed on top of the hood (using blanket to protect the paint, in an effort to reverse the bow. I do not know how effective that is, but I can see were with enough weight and heat that bow might be flattened out to some degree.

We have minimized the possibility of the hood bowing by opening and raising the hood of our 69 GT500 any time the car is in the garage or at a car show, in order to eliminate the hood springs applying spring pressure on the hood. I do not know how effective or useful our effort really are, but our hood is quite a bit flatter than other 69-70 Shelby hoods I have see in person or via photographs. In your case, with the various contours, your hood may be more or less susceptible to bowing. But, I would suggest you also leave your hood up when it is parked, especially with a hot engine compartment, to prevent needless bowing. The yellow Shelby in the embedded photo has a very extreme bow to it, sadly enough. Below are some links re: what causes the bow, and some suggestions on how to correct it.


https://www.vintage-mustang.com/threads/how-do-you-fix-the-dreaded-shelby-hood-bow.1185820/
https://www.saacforum.com/index.php?topic=8811.0

I toyed with the idea of modifying the hood to add an air exit. An open space for this would be between the two RAM air entrances. I looked at many different options out there and they seem to be effective when placed right behind the fan. Also, there would be a low pressure area which will help suck air out. However, although it may be practical, I think it will make the hood too busy and will take away the beauty of the hood. So even though I race my car, it is still a classic car that I enjoy on the street and car shows so I want to keep the exterior as close to stock as possible.

I am a plastics engineer for trade and totally understand what you mean with stress and temperature. Fiberglass is made out of a thermoset resin (probably polyester or vinylester in this case) and glass fibers as reinforcement which suffers less from creep than standard plastics. However, as you noted, it is important to keep in mind. It would be ideal to install the hood in a way that the stresses are minimized which involves adjusting the hood stops and making sure there is not too much load on the RAM air gasket. Off course that this is easier said than done so your option of leaving the hood unlock for long-term storage is a good idea.

 

[tony-muscle]

So today I drove the car to the body shop so he can look at it. Once I complete the fitting he will just work on the prep and paint. He won't need the whole car so I will bring him the stock and fiberglass hood for him to work on it over the winter break.

As an update I installed the springs from McMaster Carr and they work great. They hold the hood up, but once you close the hood about one inch it will go down. I think a little higher rate would work better but this is all they have with those dimensions. These springs are rated to 25 lb/in. I think springs between 30-35 lb/in would work great. I will try to modify these springs to they can extend a little more to add a little more of initial force. The springs are the "Music Wire Steel Extension Spring with Hook Ends, 7" Long, 1.5" OD, 0.177" Wire Diameter", p/n 5667N385 (https://www.mcmaster.com/catalog/128/1405).

 

[Ripper679]

Wondering... i have a steel ram air hood.... (I have aftermarket repo hinges and springs... probably China made) would you recommend a lower spring rate from McMaster as well for a steel hood instead of using whatever my repop springs are? Or is my whole combo here no good? Is there a set that actually works that dosent have a bunch of play in the hinges that will hold up?
Sorry.....
Not my intent to hijack
But you seem to be a bucket of info Tony!
Thanks!
Manny

 

[tony-muscle]

Wondering... i have a steel ram air hood.... (I have aftermarket repo hinges and springs... probably China made) would you recommend a lower spring rate from McMaster as well for a steel hood instead of using whatever my repop springs are? Or is my whole combo here no good? Is there a set that actually works that dosent have a bunch of play in the hinges that will hold up?
Sorry.....
Not my intent to hijack
But you seem to be a bucket of info Tony!
Thanks!
Manny

There may be others that know better. My stock hinges also have a lot of play and i dont know which repos are better. As for springs i know NPD sells a few depending if you have RAM air or not. I had to change mine because the fiberglass hood is much lighter. If your hood is not hard to lift or to lower then your springs may be good.

 

[tony-muscle]

This past week I was able to patch the recess opening on the hood that was needed to fit the RAM air setup. Not a professional grade finish, but it will be mostly covered once the hood gets painted. I also drilled all the holes to install the windshield fluid sprayers and added some steel bars to attach the bolts of the hood latch. I just wanted to further reinforce the hood latch attachments.

Next steps are to fit and align the hood again, and then take it to the shop for paint and installation of hood twist locks.

 

[c9zx]

Looking Good!

 

[droptop73]

Nice work!

 

[tony-muscle]

Well, today the body shop guy stopped by to pick up the hood for painting. He took the stock one to use as a pattern. I can't wait to see how it looks like. I will post an update once I get it back.
I was also able to finally weigh the steel hood. It came to 78 lbs bare. The fiberglass is 36 lbs bare, so that should shave 42 lbs from the front end. I was thinking the steel hood was closer to 100 lbs but I was way off.

 

[Cleveland Crush]

42 lbs is a nice savings off the front.

 

[tony-muscle]

42 lbs is a nice savings off the front.

Agree. Can't complain, but as a hot rodder, I always want less weight.

 

[Hemikiller]

The thing is so big and awkward, it sure feels like 100lbs.

 

[PoFoMoCo]

.... I was thinking the steel hood was closer to 100 lbs but I was way off.

You forgot to factor in your age my friend.

 

[tony-muscle]

Hood is painted. I will be picking it up within the next couple weeks. Don't ask how much I had to pay! A lot more that what I was dreaming of. This guy is very meticulous so it looks beautiful. He put a lot of hours and used PPG paint. It will definitely look "too" good once on the car.

 

[Cleveland Crush]

Very nice

 

[Steve McMahan]

It’s only money . . .

That’s what my wife says.