Separating Bonnet Skin And Frame

[gav240z]

Some updates, cut the bent distorted section out and have "tacked" in the new piece (ignore the flash rust). Going to offer it up to the car and see how it sits before committing to welding in permanently. I've had quite a lot of help from Charlie my course instructor due to a number of issues I've encountered. It might look like a simple piece but it's deceptively difficult.

[gav240z]

Does anyone have tips on hood/bonnet alignment techniques on an S30Z?

 

Last night I trial fitted the bonnet onto the the car.

 

 

I am thinking I need to remove the front grille to make it easier to access the hinge bolts on each side.

 

The passenger side sticks up above the guard as you can see in the photos.

 

We haven't fixed the skin to the frame or welded in the new piece completely yet. Since we want to see how it fits on the car first.

 

If I recall correctly the bonnet sat on the car ok before I removed it. However going to fit it again later and it sits a bit funny.

[Geos260]

hi gave, they all seem to sit high near that section half way up the bonnet when you close it, my original one is like that and even the new after market one i got is the same, my mates had the same issue, they never line up, i had to drill the bonnet hing holes  to be able to do some adjustments on my bonnet, also dont be afraid to twist the bonnet when u tack the frame up, or put a piece of timber along the side of the bonnet and press on it, but not too harsh so u dont warp it...all fun and games till they do ur head in lolll

[gav240z]

Yes I was afraid that would be the case. The problem working with a damaged bonnet to start with is I don't know how out of shape things are or where to start working from.

 

I have a feeling the bonnet frame is slightly out of whack so I will try twisting it as suggested to get it more "aligned".

 

This is why I was looking at starting with another known straight bonnet.

I think bonnet alignment on an S30Z is probably 1 of the hardest panels to get right to be honest.

 

The alignment of the bonnet on my 72 is out of whack too at the front and I've been wanting to change it. At least I'll get some practice here first where scratching paint is ok.

[Geos260]

keep in mind these cars arent young anymore, they where never perfect of the production line ps  all these years on the rd and subject to all sorts of twisting and metal flexing, its hard to get them

 

perfect, and even when you do after putting it back together, one day u will be washing it and think what the hell? i had that gap perfect lolll then you learn to turn the blind eye and keep washing or

 

else it will sit in your garage and never driven hahaha  i see new cars and i mean expensive cars and the gaps are out....i speak to some of the guys at car shows and when your checking out there

 

rides and u will find they all say the same thing, can never get those gaps right lolll

[gav240z]

Don't tell me that, my OCD is going to go crazy!

 

I will see how I go this weekend, it's going to be a lot of hours of messing about and swearing I think .

[gav240z]

Well 5-6 hours of working in a hot sweaty garage wrestling with torsion bars, hinges, fenders, spanners etc..

 

It's not fun!

 

But I think it's getting closer to looking right on the car.

[gav240z]

Can you spot the bent torsion bar? I've got them removed for now while I play with the alignment. Too hard to adjust things with them fitted in place.

[PB260Z]

You've been busy.

Making great progress

[gav240z]

And... I fitted the torsion bars again.. Guess what? The passenger side about mid-way up the bonnet sits up again lol..

 

I think the frame might be "tweaked" from the front-end impact all those years ago. Since the motor was out of the car I climbed under the bonnet and closed the bonnet while I was inside the engine bay (it was like an oven in there last night with the heat in Sydney).

 

Anyway I can see on the drivers side that the bonnet frame comes a lot closer to the strut tower bolts than on the passenger side.

 

With the skin attached and the bonnet attached to the hinges (which move and flex) it's hard to "tweak" the frame.

 

So tonight at the Tafe class I'll talk to the teacher about it and see what he thinks re: twisting the frame etc..

 

The other problem is, with the skin and frame removed, the skin sits a little "fat" around the edges and therefore impacts the way the bonnet sits in amongst the other panels etc..

 

I will see if I can get a good "bonnet" to test out and see if the same issue persists or if it's just this bonnet.

 

It's a bit of a guessing game and you sort of have to tack things into place without being 100% sure it will be correct later when everything is buttoned up.

[gav240z]

Welded the piece in completely and used deoxidine (phosphoric acid) to clean the surface rust off the bonnet. Quite a bit more fettling to be done with this bonnet.

[gav240z]

Learning quite a bit about heat shrinking to reduce the high spots in the bonnet and get the profile of the damaged side inline with the other side.

 

It's not easy to tell in photos but the shape looks a lot more correct, although still a long way to go..

[gav240z]

And.. lesson of the day. Don't use zip cutters!

 

The cutter I used to remove the spot welds is not ideal, it cuts too large a gap. The zip cutter is only really useful for removing panels you don't intend to ever put back. Instead use a spot cutter drill bit that will cut a smaller hole and you can easily patch it up again.

 

To fix the situation I had to use a copper plate behind these holes and a small metal circular tab and then zap it in with the mig and then grind down the excess material. Takes ages!

 

Another guy in the class was fixing a similar issue for another bloke who used the same cutter on a cowl panel. He was using a TIG though! After seeing the TIG technique I will try this down the other side of the bonnet. Although I'm told it's not as easy as it looks, but I wouldn't mind trying TIG, now that I've got better at MIG and Oxy.

 

 

[Brabham]

What is a zip cutter Gav? Got a pic of it?

 

Cheers

[gav240z]

What is a zip cutter Gav? Got a pic of it?

 

Cheers

 

It's the cutter on the first page of this thread. It leaves a large circular hole around the spot weld. Instead it's better to use a drill piece that cuts the spot weld itself, leaves a smaller hole and can be easily plug welded instead.

 

I spent ages trying to plug these up last night, problem when welding near the edge of a thin panel is that you blow holes in it as you can imagine. So I got good at doing small zaps. I've still got the other side to do however. Also when using mig you add lots of excess material which results in lots of grinding after. TIG is the way to go if I can next time.

[gav240z]

Oh boy,

 

Anyone have tips for me on how to get this alignment right? With the torsion bars in the bonnet sits high on the passenger side of the car. If I push it down flush I can get the panel alignment acceptable, but it won't sit down that low.

 

I've tried adjusting the hinges and moving them up and down, I haven't elongated the bonnet mounting points (would rather not do that as it seems like a butchers method and I'm not sure it will help here).

 

The car did have a light front-ender on that side, so I'm wonder if that's pushed the area in front of the radiator support down just slightly. Unfortunately I haven't been able to find a good solid / straight bonnet to test out (to see if it's the bodywork on the shell or the bonnet itself).

 

But if anyone has ideas on how to improve this I'm all ears!

 

NB: Yes the bonnet skin and frame are not welded back together and that will help (a little) since it will pull the skin closer to the frame, but it will still sit a bit higher than it should and it's just that side!

[Retro Z]

Heat up one of the torsion bars with oxy or propane until almost cherry red and it will relax some of the tension.

[gav240z]

I assume that involves bending it a specific way? To pull the bonnet lower? I guess it needs to "twist" correct?

[Retro Z]

Shouldnt need to bend it. Leave everything all hooked up. Just after u heat it, push the bonnet to the desired position and cool the rod with water.

 

May take a few attempts. Just dont overheat or over bend the torsion bars or they will lose all of its tension.

[Geos260]

hey gav, where abouts in sydney are you mate? i have an original bonnet that you can try on, if you want pm me your address and if your close to me i will bring it over in my van and help you out with it, or will work something out 

[gav240z]

hey gav, where abouts in sydney are you mate? i have an original bonnet that you can try on, if you want pm me your address and if your close to me i will bring it over in my van and help you out with it, or will work something out 

 

Thanks mate, I'll send you a PM.

[gav240z]

Well thanks to George (Geos260) who dropped this bonnet around today.

 

It's got a lot of surface rust from sitting around and the front nose has had a nudge in the past (bogged up) but the overall side profiles seem to remain relatively untouched.

 

https://goo.gl/photos/6rSjPR6R9q6ENaj68

 

I've only mucked about a little bit, but already the alignment is better than the other bonnet.

https://goo.gl/photos/6QBqXzb3hCKZe9cp8

 

This is with the torsion bars in and the bonnet shut. I'm just pressing down on the headlight surround (sugar scoop) because I haven't bolted it down.

 

https://goo.gl/photos/BNAv4YPSgczfvPnr9

 

The gap here looks worse in the photo than it is and I'm sure could be adjusted given a few minor tweaks.

https://goo.gl/photos/uDE1g15MUYevLTUCA

https://goo.gl/photos/a1yR1o78f6EEjPTh9

 

Gap up near cowl is good. (again some minor tweaking required).

https://goo.gl/photos/1zoJ9RTR73UVnvkD9

 

It's actually sitting a little high on the driver side now.

https://goo.gl/photos/29Xg8G46TKYzcPpX9

 

You can see the front of this bonnet droops just a touch.

https://goo.gl/photos/LFTp9vxjxR4BMrSy8

 

Closed with torsion bars in (not sitting high).

https://goo.gl/photos/moXJXadHt7ywKeb57

https://goo.gl/photos/JEtmcQ9wnZMP6FCP7

https://goo.gl/photos/2N3MnymS1mrFiKWQ9

 

I only really messed about with it for an hour so considering how much gymnastics I've done with the other bonnet so far, not bad!

 

I did notice that the mounting points on the bonnet where it attaches to the hinge were slightly elongated on 1 side so that might also be at play here.

 

The other thing with the original bonnet is that it hasn't been buttoned up yet (lips folded over), spot welds to join frame and skin and that in itself might cause the bonnet frame to sit a bit differently and perhaps allow for better fitment in general? It's at times like this you can only sort of guess that you're almost in the right place before finalising things and welding it into place.

 

In the interim though I've got some high spots to take care of and some other detailing work because spotting it into place. So I'll have a bit more of a play around with the alignment and see how it goes.

 

 

[gav240z]

So this has been a lot of faffing about...

 

So thanks to George for letting me borrow his rusty (surface mostly) bonnet to compare alignment with the 1 off the car.

 

Even though this bonnet had had a couple of love taps of it's own the side profiles down the bonnet appeared to remain as factory. This served as a good reference point as to where my bonnet should roughly follow or line up.

 

A tip I've discovered is that you really should bolt up the fenders and sugar scoops along with fitting the bonnet latch / catch because all these things impact the way the bonnet ultimately sits on the car.

 

 

As you can see the bonnet on this side still sits a little proud of the fender by about say 5mm but that's because it hasn't been welded (the skin) onto the frame yet. So it naturally wants to sit high. My tafe teacher last week helped me spot a couple of spots where the bonnet frame wasn't quite right, which is very subtle to the untrained eye and I reckon this has helped a little with some other minor adjustments I've been up to.

 

For example in the panel beating business there is a saying "whatever works".

The front right nose area of the car was sitting a little low and wasn't coming forward enough. I was able to coach it up a few mm using a jack under it and a block of wood. But getting it to come forward is a little more tricky. Still I think it's close enough for now to allow me to get the bonnet alignment looking a lot better than before.

 

It's not sitting perfect at the rear here because the skin isn't folded around the frame. But if you give it a gentle push down it will sit nicely.

 

Another issue with this bonnet is that it used to have body filler up toward the passenger end of the bonnet from a previous ding or dent put in it, this had a low spot that we unfortunately made worse trying to repair it, in fact I've made a lot of mistakes during the course of this bonnet repair. I'm actually surprised it's turned out this well so far. I really thought I'd need a new bonnet. Doing some heat shrinking (which I'm only sort of good at) I managed to shrink this area back into shape and then the Tafe teacher came over and gave me a few tips on where to focus my heat shrinking.

 

We then filed up the bonnet, there is still a few minor low spots but we can use regular body filler (which would be no thicker than 5 or 10 cent coin.

Engineers blue dye is used to help spot the low areas when filing. Most of the darker ones are so small you can hardly feel them when you run you fingers over them, but they are there! Body filler should make them disappear.

 

Knowing my luck by the time I get this bonnet looking right a NOS 1 will appear. It's always the way it works..I guess at least this 1 is the original off the car.

 

 

 

 

 

 

 

 

[gilltech]

Great work!

[gav240z]

Well not much to report, but was talking to another fellow at my tafe class who told me about this shrinking disc you can get. It seems like a better method of hot shrinking a panel.

 

 

and a demo here:

 

 

I might have to give it a try..