Hood Flies Open driving down highway in my 74 620

[Cardinal Grammeter]

While I was on a 2-lane state highway, traffic was light and I knew the road.  Watched the yellow line out driver's window to get it slowed down, then using memory, pulled off on side of road which I thought was clear - it was.

 

Good news is windshield was not broken.D

 

Cowl took some abuse, hinges bent back, one corner of hood bent but fixable (whether I do it or just put back as is, don't know.)

 

I was right in front of Tasty Land Ice Cream stand and 2 guys had some tools and we took the hood off and put in bed.

 

I think this once happened to me before (40 years ago-ish) - with a Studebaker...

 

Just when I thought I was done with this project...

 

Oh, I thought I had the hood latch adjusted correctly with the safety latch engaging properly.  Did not have the fender bumpers in so hood is doing its little torsional dance in the wind - I guess that was enough to work the latch loose.  The hook looked ok, but the bracket looked a little ripped where the hook evidently caught.

 

Ironically, this truck was "butchered" with hood pins which I removed and soldered the holes up in the hood - I wonder why they did that (!)

 

Now I'm all paranoid about seeing this never happens again.

 

[flatcat19]

Now I'm all paranoid about seeing this never happens again.

You should put some hood pins on this thing.

[flatcat19]

Seriously though, what does your latch pin and spring look like?

[flatcat19]

...and, no #fml threads...

[Cardinal Grammeter]

The spring was so weak it would not pop the hood up when latch pulled - so I found an inner spring at the hardware store - just enough to pop it up.

 

Something was changing in the safety hook though:  When I aligned the latch/hook, you could drop the hood from maybe 6" open and it would lock nicely.  Then the hook started not sliding in which case I had to hold the hook open to get the hood to latch.

 

It was a double failure:  latch and then hook.  Maybe I should take some pics and get some opinions.  I can say the hook looks fine but what it hooks on to doesn't look right - it's bent and notched.

 

I'll try to get the pics up tomorrow.

 

EDIT:  Wow, NO body panels on RockAuto.  I thought just a couple months ago they have $100 hoods....  No valance.  No grilles. Nadda...

[flatcat19]

Nope. And good luck finding Datsuns in the junk yard on the east coast.

[Cardinal Grammeter]

Pics

 

Nothing looks obvious.

 

Interior latch spring is very strong and cable very smooth.

[flatcat19]

Your pics are broken.

 

 

C/P the IMG code here.

[Rjawm]

 

 

 

 

 

 

 

 

 

 

 

 

[flatcat19]

Why are there shims in the top plate of the latch assy?

[Cardinal Grammeter]

Thanks for the pic post - I guess that means the link did work.

 

 

Shims needed to get the hood elevation same as fenders.  The latch pin was adjusted out as far as possible and the hood was still too low.

 

Probably an issue of previous owner(s) when the put the fenders on.  They had to weld up the tops of the inner fenders and the match there with the fenders was poor - no fasteners used along tops of inner fenders.

 

I still don't understand why I needed so much shimming since the fenders bolt properly to the core support.

__________________________

 

WEIRD HOOK WEAR:  If you look at the hook, it looks like it has worn away near the tang.  There is a corresponding slot worn in the latch.  If the hook didn't slide into the slot when hood closed, then tang engagement would be compromised possibly.

[hobospyder]

Hood bumpers for correct height on the hood. They attach to the fenders.

[Cardinal Grammeter]

But even if I have the correct bumpers, I'd normally adjust the hood so there was no interference or binding - or is the intent to put preload on the bumpers?  And although the hood is as "thin as paper," any preload would put more load on the latch.  But then it wouldn't be torsionally flapping.  Back to Square One:  what caused the failure?

[Jesse C.]

Bummer! Those latches need to be set up properly and be in good shape. By the looks of the pics, it was doomed from the start. If you have to shim the hood latch to adjust the hood, it may be a sign that something is seriously off. And Datsun latches are notorious for giving up when they get pretty worn, like this one. 

 

And this is why I am putting hood pins on my car and eliminating the hood latch system altogether. 

[Cardinal Grammeter]

I don't know what else I could do to set it up better.  The pin is dead center on the latch bore. 

 

Although the safety hook works when opening the hood, I never checked to see what its engagement was - it's possible it was engaging on the tip of the tang.

 

I really don't want to put the hood pins back in...  However, some modern techy flush pins might be another matter.

[datzenmike]

Bummer! Those latches need to be set up properly and be in good shape. By the looks of the pics, it was doomed from the start. If you have to shim the hood latch to adjust the hood, it may be a sign that something is seriously off. And Datsun latches are notorious for giving up when they get pretty worn, like this one. 

 

And this is why I am putting hood pins on my car and eliminating the hood latch system altogether. 

 

 

AAggggh! Never use hood pins. Get a length of chain and secure it to the rad support. Have a strong hook or latch on the end and something to latch to on the hood. Release the hood, lift up enough to reach in and unhook the chain. Pins look like fuck, are cheaply made, rust out the hole and are a pain in the ass to unlatch and re-latch. Never drill holes in a Datsun, that's mutilation..

[hobospyder]

I usually put hood down, engage safety latch and then push down hard until it engages the locking loop or whatever and then give a strong pull upwards to ensure proper latch connection if I'm under the hood.

[hobospyder]

Never drop them closed. I broke a headlight doing that

[Jesse C.]

AAggggh! Never use hood pins. Get a length of chain and secure it to the rad support. Have a strong hook or latch on the end and something to latch to on the hood. Release the hood, lift up enough to reach in and unhook the chain. Pins look like fuck, are cheaply made, rust out the hole and are a pain in the ass to unlatch and re-latch. Never drill holes in a Datsun, that's mutilation..

 

Thanks for caring, I think, but I can't run a chain on my hood and rad support. I am getting aluminum pin sets

[datzenmike]

Hood pins hurt as much as looking at pierced nipples. :lol:

[hobospyder]

my supervisor has pierced nipples. the crew knows this because he wears tight tshirts instead of the button ups he's supposed to and they poke out every morning making it look like he has 4 nipples........

 

what i'm trying to say, is don't be like my supervisor

[Rick-rat]

 

 

If you want hood pins, go for it. It's your Datto. Better than trying to find a new hood or other damage that can occur if the hood comes open.

[tr8er]

Hood pins hurt as much as looking at pierced nipples. :lol:

I agreed with you until now.

[tr8er]

my supervisor has pierced nipples. the crew knows this because she wears tight tshirts instead of the button ups she's supposed to and they poke out every morning making it look like she has 4 nipples........

 

what i'm trying to say, is don't be like my supervisor

Fixed for everyone's sanity...

[Cardinal Grammeter]

SOLUTION:  Redesign Safety Hook:

 

The problem with the hook is that its engagement shape is an "L" instead of a "J".

 

The L can slide off whereas a J cannot.  (Studebakers used J hooks which were massive.)

 

Depending on vertical engagement, I may have to add metal to the hook (oxy-acetylene weld ONLY - want fully annealed and not brittle) to have enough room to produce the J profile.

 

I may wrap some .25 sheet around the J so that the section is a T which is much stronger - OR add sheets to both sides of the hook to make it wider.

 

Might even be able to use washers for the form itself.

 

The latch will probably get a piece of horizontal rod to engage the J hook.

 

This will not solve the problem of the hook unlatching, however it will perform the safety function.  NOTE:  The striking thing about the latch pin is that it is so small.  The fact that the pin spring weakens to the point where it does not pop the hood up is another indication of not enough "safety margin" in the design.

 

NOTE:  ALL the fasteners to the hood, cowl, and hinges were either just snug or completely loose - I took the cowl screws out with my fingers.  I still maintain too much vibration coming from engine.  And that vibration could also work to vibrate the latch pawl off the pin.

 

Hummmm.... which leads to weakened springs:  For the pin to pull out of the latch, it has to get past the pawl and the only way for that to happen is the pawl has to move out of the way.  Combinations of friction, vibration, load could walk the pawl open.  This could be countered with a stronger pawl spring - which I will also fab in.