Hood Flies Open driving down highway in my 74 620

[hobospyder]

Fixed for everyone's sanity...

yeah.... if only

[Cardinal Grammeter]

If you are compelled to drill holes in virgin hood metal, just don't get "muscle car" hood pins - too many cars were butchered with them.

[Cardinal Grammeter]

Hey, I like slutty women!  They're so... slutty!

[datzenmike]

If you are compelled to drill holes in virgin hood metal, just don't get "muscle car" hood pins - too many cars were butchered with them.

 

I bought a new '70 Dart 340. It had the 'performance hood' package which was flat black paint and hood pins. If they came factory, fine with me. Putting them on is pretentious.  

[Jesse C.]

I've had a hood open on me, luckily at a slow speed and no damage occurred. And I have had quite a few cables break on me as well. My car is not a super sano stock vehicle, it has been flared and was gutted at one time. Now I am re-building it and I am getting rid of the hood latch system. The pins will be doing what hey have been made for, to hold the panel down. Yeah, they are not for everyone, but, at least I am going old school and using the traditional style vs. the ricer slide jobs. 

 

So yes, in the end, it is my car and I will drill holes that will make Mike cringe. Oh well! 

[Cardinal Grammeter]

I guess I'm jaded.  I did a lot of street racing in the early 70's with a very quick supercharged Studebaker Lark and there were all these kids that had really slow cars yet put all these "decorations" which implied that their car was fast.  Wheel and muffler/exhaust fetishes were the most depressing.

 

Were 620's ever factory raced?  If there was any historical hood pins - maybe in Japan - I'd go that route if I was going to pin it.

 

I'm an engineer, a structural one at that, and to be beaten by a crappy latch design - well, them's fightin' words.

________________________

 

NOTE:  The one post that mentioned "pulling up on hood after closed" is a pretty good idea.  It is always possible the latch did not fully engage.

 

However, the acknowledged tendency for Datsun hoods to fly open is troublesome.  It seems to be across many models.  Perhaps the simplest explanation is the reason:  the latch is simply not big enough.

 

I'm also going to try some "ghetto" hood bumpers:  pieces of pipe insulation on the core support top edge.

[Cardinal Grammeter]

MORE DIAGNOSIS:

 

Finally have the hood straightened (came out better than I expected - if I get serious about painting it, it will only need a little more dolly work.)

 

Will have to tweak the hinges a little to get the right alignment.

 

BUT

 

Finally had a chance to see how the Safety Hook performs:  It's a mouse trap:  the cheese goes on the manual release and the big spring is the hood aero load.

 

Unlatched on the hook, lifting up on hood, a shockingly small amount of force on the manual release lever will cause the hook to disengage - the main force keeping the hook engaged is the spring.  And since it is clear that the pin pop-up spring loses its temper, it's a safe bet the other springs do too.  However, the hook should not rely on spring force to function - the spring function should be to position the hook so it gets full engagement - not to keep it engaged.

 

Putting some rake on the hook L profile would obviously address that problem too, but there isn't enough metal there in my opinion - the hook could get ripped/bent open if it's section is reduced with a rake cut.

 

__________________

 

It's going to be a day or two before another repair update...

[Rjawm]

 

 

 

I'm an engineer

 

 

 

Sooooo much explained in this one bit of information.

 

All your posts begin to make so much more sense now...

[KoHeartsGPA]

Agreed ^

[Cardinal Grammeter]

OK you Brainiacs, how do I fix my latch?

[Rjawm]

I'd start with fixing the obvious previous front end damage that led to the need of all those shims being required to match hood to fenders...long before I tried to re-engineer the hood latch to match the damaged front end that's for sure.

 

But I'm just a brainiac car guy with real world auto body experience not an engineer, so take my opinion and info, mull it over, over think it, and then claim the new regurgitated version of what I said as an engineer spec proposal.

[Cardinal Grammeter]

I posted this pic early on and someone should have seen this right away: the angle of the "barb" is greater than 90 degrees.  This literally makes the safety latch a mouse trap.

 

The angle of the flat is about 92 degrees from the vertical edge (the aft edge of the hook, just above the horizontal flat,  is worn away from rubbing on the latch.  If you sight along the unworn edge, you will see the angle of the barb is about 92 degrees.)

 

This means the barb will actually slide off and only the little springs are resisting this.

 

Look up any Datsun hook - especially Z-cars, their pics are everywhere and you will see an angle of no more than 70 degrees.  There has to be a bone fide barb on the end of the hook so it can't pop off.

 

 

here is what it should look like:

 

 

 

[Rick-rat]

Quit trying to reinvent the wheel and just drive your truck, put in hood pins or remove the hood and you will not have this problem again

[Cardinal Grammeter]

Turns out the 1200 folks are all over this (like just about everything else Datsun - these guys are tech savy)

 

There was a recall:

 

The 1200 Webpage about Hoods

 

Needless to say, my 620 has the crappy design and where did I get this latch?  It did not come with the truck since they stripped it due to hood pins.  Still have not been able to find a single pic of a 620 (or 720) latch yet to see if they have the good catch profile - I'd just as soon buy one that works.

 

 

_________________________________________________________________

 

EDIT:  It is possible I have the wrong hood latch part.  Here are two 620 latches FS on eBay right now:

 

This one is from Thailand and it looks like it has the redesign profile:  Note the length of the hook is just a bit longer than the Spring Pin.

 

This one is from Mexico:  (it looks like it has a longer safety catch, but difficult to judge since only one view:)

[tr8er]

I believe that hook is your issue. Along with the front end damage. If you want pins, just do it. Those who have bought old cars with pins already done hate them. It's just another think to deal with. But that's not your deal unless you care about it. Regardless, I'd fix the latch. Get it to factory without shims, and with jhook. Then do pins if you choose to. It all beats having a hood flip while driving.

[Cardinal Grammeter]

I think I may have the wrong part on the hood.  I'm trying to get vendors to supply pics of the hook profile - I won't buy one unless I see it.

 

There is no front end damage - I had it all apart.  Fenders adjusted as low as possible on core support.  So I'm hoping its the wrong hood post - the new ones appear to have 1 more turn in the pop-up spring - they may be longer.

[datzenmike]

My 710 has this J or hook style. Even the lever looks the same.

[flatcat19]

I think you need to ask someone to measure their 620 latch and compare it to yours.

 

 

I have been told 521s and 620 latches are close to the same. As far as I have seen the only difference is the mounting locations are different.

 

My 521-from center of pivot for the hook to the inside corner of the J is roughly 1 3/4".

[hobospyder]

Didn't you steal a 629 hood latch for your 521?

[flatcat19]

No. I just used the pin and spring.

 

I tried to take the whole latch. That is how I know the mounting holes are different.

[Cardinal Grammeter]

Mine is 2" from the hook pivot rivet to the "tip of the barb."

 

My hood latch post is 3" from the tip of the post (bottom) to the bottom side of bracket it screws in to.  Also, my pop up spring has 4 turns of what seems to be a smaller wire diameter - it is significantly too weak to pop the hood open - I had to add an inner spring (see my pics.)

 

I filed a nice J barb into mine.  Makes a big difference when opening the hood: 

 

BEFORE:  I'd pop the hood and then lift the catch lever to disengage.

 

AFTER:  I pop the hood and cannot lift the catch lever until I push down on the hood moving it out of the J barb.  NOTE:  this is a good test to see if your safety hook is engaging in a "barb"/J-fashion or it's working like an L pawl held in only by 2 small springs.  If you can simply lift the lever, you're at risk of hood-L-mania.

 

I'm really pissed over all this.  My hood was straight and had only minor rust.  I did a journeyman straightening of it, but there are numerous dents when it wrapped over the cowl and wipers on it's way to the windshield.  My truck would have been 100% straight including the tailgate before this...  (I even found a good OE front edge trim...)

[Trophy24]

I bought one of those hood latches from Mexico. I can post a pic when I get home Saturday

[Cardinal Grammeter]

Thanks Trophy24!   Will be interesting to see what that hook shape is.

 

I also found there was actually a Nissan Part Number for hood pins:  99030-RR120 Pin Kit-Hood Catch

 

http://datsun1200.com/modules/myalbum/photo.php?lid=24612

 

If I was going to put hood pins in, I'd at least use the Nissan OE ones.  They are better than the old muscle car types since the clips are built in.  (there is a pic of a blue hood with this style)

 

[datzenmike]

 

Here's what the Dart pins looked like. The clip was on a lanyard. Totally a dress up part on the Performance Hood option  package including the flat black non reflective paint.

[Cardinal Grammeter]

I have no problems with hood pins on race cars OR muscle cars that came with them.  I think the Ford Cobra Jets came with them too.  Obviously the Mopars  especially the 4-pin black lift off 6-pack hoods.

 

But they just don't belong on the Datsun.  At least get period correct ones.

______________________

 

 

Rachel Blooms  OCDance  and I Steal Pets for good measure.  ...and what the hell, I'm So Good At Yoga

...as the maggots ate into his brain