Shelby Guru Question - NACA Duct Hoods

[Benny]

G'day fellas, I understand this question may have been discussed a thousand times but here we go. The cause of the bow in the NACA hoods, is it from poor quality with production, wrong jig, bad fibre glass or pressure from the hood springs pushing forward onto the hood pins causing the hood to bow or is it heat from the engine bay etc etc etc or does all the above apply? I'd like to know & there may not be one answer, your knowledge & information will be appreciated, thank you.

[Bob Gaines]

G'day fellas, I understand this question may have been discussed a thousand times but here we go. The cause of the bow in the NACA hoods, is it from poor quality with production, wrong jig, bad fibre glass or pressure from the hood springs pushing forward onto the hood pins causing the hood to bow or is it heat from the engine bay etc etc etc or does all the above apply? I'd like to know & there may not be one answer, your knowledge & information will be appreciated, thank you.

I can sense your frustration. Any one of those things or a combination could be the cause of the bow but probably not all on the same hood. There are things that you can do to strengthen the hood but that requires surgery to the structure. There are a number of things you can do to address the symptoms . Some hoods never have a problem. 

[Mongo]

Also ad to all those causes the color (dark colors) of the car in the hot sun with a 428 running hot in traffic vs a white 351 car!

[FL SAAC]

Hi there, 
cause of the bow is engine and ambient heat + 50 plus years + factory stock springs on the hinges.

When we painted both our 1969s the craftsmen that worked on our cars used a tried and true method to some what correct the issue.

Each hood sat outside for months in the Florida sun. Cement blocks  where carefully placed on the bends. Over a period of time this eased the bend. Once it was some what acceptable, it was prepped and painted.  We purchased lighter hood springs that are adequate in holding the hood up.

Good luck
Not a Guru - just a regular guy

[427hunter]

Why does this matter? It's just the way it is, the cars are 53 years, let it go.

[Benny]

G'day fellas, I understand this question may have been discussed a thousand times but here we go. The cause of the bow in the NACA hoods, is it from poor quality with production, wrong jig, bad fibre glass or pressure from the hood springs pushing forward onto the hood pins causing the hood to bow or is it heat from the engine bay etc etc etc or does all the above apply? I'd like to know & there may not be one answer, your knowledge & information will be appreciated, thank you.

I can sense your frustration. Any one of those things or a combination could be the cause of the bow but probably not all on the same hood. There are things that you can do to strengthen the hood but that requires surgery to the structure. There are a number of things you can do to address the symptoms . Some hoods never have a problem.

Thanks Bob, your experience & wealth of knowledge is greatly appreciated. Its good to hear there may have been a numbering of contributing factors to why some hoods may have bowed whilst others didn't, cheers.

[Special Ed]

Recently bought a 70 shelby out of Alaska and it had very little hood bow but the guy only drove it in the winter at night ALL NIGHT no hot sun problems there!!!!!!!

[shelbymann1970]

My vert spent it's normal life in France and Belgium before I coddled it in 1985. No bow here without springs. I recommend no springs on a 68-70. You can install light tension "Branda" springs by hand for shows or use a prop rod or I think Mr Gains used a chain method before on the hinges. My friend's Gt500 red car has one of the worst bowed hoods I have seen to date and my GT350 red has one of the best. It spent many years in Texas.
Bow? What Bow(pic below).... Seriously I was going to take my friend's hood and do what Tony said he did in his post with weights. Then if that didn't work make cuts on the inner hood with weights but I would also cut out a template to see the progress if any without mounting the hood back on the car. Good luck

[FL SAAC]

My vert spent it's normal life in France and Belgium before I coddled it in 1985. No bow here without springs. I recommend no springs on a 68-70. You can install light tension "Branda" springs by hand for shows or use a prop rod or I think Mr Gains used a chain method before on the hinges. My friend's Gt500 red car has one of the worst bowed hoods I have seen to date and my GT350 red has one of the best. It spent many years in Texas.
Bow? What Bow(pic below).... Seriously I was going to take my friend's hood and do what Tony said he did in his post with weights. Then if that didn't work make cuts on the inner hood with weights but I would also cut out a template to see the progress if any without mounting the hood back on the car. Good luck

Oui, oui the weights over a period if time,  tames the hump

[FL SAAC]

Why does this matter? It's just the way it is, the cars are 53 years, let it go.

+ 1

[FL SAAC]

Recently bought a 70 shelby out of Alaska and it had very little hood bow but the guy only drove it in the winter at night ALL NIGHT no hot sun problems there!!!!!!!

Eddie, Eddie, Eddie you know that :

Extraordinary claims require extraordinary proof....

[Cobrask8]

On my 68, the fiberglass hood bowed with the stock springs trying to close it. I removed the springs and drilled holes in t the hinges that aligns in the open position. I used hood pins on lanyards to lock the hinges when open.

[shelbymann1970]

On my 68, the fiberglass hood bowed with the stock springs trying to close it. I removed the springs and drilled holes in t the hinges that aligns in the open position. I used hood pins on lanyards to lock the hinges when open.

On my 68 I used a prop rod to keep it open. Then hand installed the light tension springs. I could also remove them by hand. Did it more than a few times at car shows. Hood was definitely "different" with the light tension springs VS no springs. I sold the car 6 months after buying "some red Mach1". Gary

[Bob Gaines]

Putting weight on the hood in the hot sun or otherwise so to push it back into shape is not typically a long term solution. It will most likely bow again under the same heated conditions.The only sure fire permanent solution I am aware of is to notch and add small sections to the inner structure so as to add tension and compensate for the flex/bow.

[FL SAAC]

Believe these are the ones we purchased