Help with Front Bumper mount Area

[Namerow]

Nice to see that the X-Y laser gave you some encouraging measurements

Re your plumb bob measurements, I think you should would be quite satisfied with a discrepancy of only 1mm in your LHS vs RHS measurements. I think that's probably within the manufacturer's original build tolerance (which, in the 1970's was probably on the order of 1.5 - 2 mm for this type of long, front-to-rear measurement).  One question, though:  Did you measure both longitudinal (front-right to rear-right / front-left to rear-left) and transverse (front-right to rear-left / front-left to rear-right)?  If you only did the longitudinal measurements, then you still don't know whether the frame is lozenged (also referred to as 'diamonded', IIRC).

The plumb laser will make these measurements more convenient and more accurate.  Trying to hang a plumb bob string from the center of a bolt hole or bolt head is not that easy to do with accuracy (especially if you're lying on the garage floor). 

At the back of the car, you should be using the 'C' points (holes in the rear subframe, just behind where the interior floor pan kicks up) as your reference.  At the front of the car, you should use two different sets of reference points: 1) the front (or rear) LHS and RHS crossmember mount holes in the frame rails, and; 2) the centres of the big holes at the top of the two front shock towers.  (1) will tell you about the alignment of the lower structure and the lower front suspension pickup points. (2) will tell you about the alignment of the front suspension's upper pickup points. 

Re the front bumper mount holes, I suggest you wait for corroboration from at least one additional owner of a damage-free Z to feel confident that they're supposed to be 'level'.  Although logic says that this should be the case, you just never know.  You have a lot of prospective time and effort a stake, so best to not begin until you're as confident as possible about what is 'correct'.   Also:  I'm leery about the float-level measurement methods that I've seen so far.  They measure relative to an inertial level, but you can't be sure whether both cars are sitting at the same pitch angle (aka 'rake angle') relative to inertial (or, for that matter, whether the floors underneath them are properly level).  Ideally, 'level' for the bumper mount holes should be judged using a vehicle frame of reference.  Your X-Y laser can do that, but the float level measurements may be suspect.

Another thing:  Note that the front and rear bolt holes are drilled pretty close to each other, which means that any errors made in sighting on the bolt hole centers (or the bottoms or tops of the bolt holes) will greatly exaggerate the measured front-to-rear angle.  If I was doing this, I'd use a compass to draw a bolt-hole-sized circle on a piece of wide masking tape and then draw on crosshairs. Then I'd stick the tape on the body panel over one of the mount holes.  Now repeat for the other three mount holes.

One last idea (which you can take or leave):  If you conclude that the bumper bolt holes really are out of whack, you might consider trying a bit of 'caveman' body alignment as a low-cost, low-impact first step.  Take some of the square tubing you have left over from your frame rig construction project and cut a pair of 8-foot lengths.  For both, drill a pair of correct-size holes at one end that are at the same spacing as the bumper-bolt holes.  Bolt the legs in place on the bumper/hinge-mount body panel, one one the outside of the panel, the other on the inside, securing them in place with two pieces of threaded rod (or a pair of really long bolts).  Now you have a hefty 8-ft lever that's solidly mounted to the bent panel.

If the front bumper-mount hole is higher than the rear one, you'll need to push down on the end of the lever. In this case, I would suggest you build a solid side-to-side wood trestle to put under the front of the front frame rails, right behind the rad bulkhead.  Also, put some counteracting weight in car's hatch area (sandbags, more left-over frame-rig tubing, a couple of willing bystanders, whatever falls readily to hand).  Now push down on the end of your lever and see if you can get that sheet metal to shift.

If the front bumper-mount hole is lower than the rear one, you have a slightly different proposition.  In this case, you'll need to lift up on the lever and that wood-trestle support-behind-the-rad-bulkhead idea isn't going to happen.  When you lift up on the end of your lever, you'll really just be trying to lift the whole front end of the car (and support frame) off the garage floor.  I'm too lazy to do the math, but I expect you won't be able to put more than 100 lb of lift onto the end of your lever arm before the vehicle and support frame start to lift off the floor.  Still, 100 lb of force on the end of an 8-ft lever might generate enough torque on the panel to shift the local sheet metal in the process.

And if none of this works, you can always move on to Plan B (hammer, dolly, torch).

Disclaimer:  I haven't tried the lever idea, so I can't guarantee that it will work.  Or be safe.  Caveat emptor.

[Patcon]

Keep in mind that all of the repair work in this area needs to be done on the jig, not on the rotisserie. The lever idea might work really well if the radiator support was out of the way. Put some force on the lever and then dolly the crumpled area behind the radiator support.

Does anyone know if the radiator support is plumb in the car or square (90d) to the frame rail?

[240ZBUILTBYME]

8 hours ago, Namerow said:

One question, though:  Did you measure both longitudinal (front-right to rear-right / front-left to rear-left) and transverse (front-right to rear-left / front-left to rear-right)? 

I measured diagonally, so rear left to front right and vice versa. I didn’t go longitudinal as I wanted to make sure it was square and not diamond as you say. But doing a longitudinal measurement as well would be prudent. 

I like the lever idea for its simplicity, however my front bolt hole needs to come up so may be less effective. As the car will lift before I get enough force on the panel I feel. When I was building the jig I purposely placed the longitudinal 3m lengths in line with the panel that the front fender rests on/bumper mounts onto, as I knew I may need to do some pulling. Also saw in @ConVerTT ‘s thread that he used  the longitudinal lengths on the jig to lever a scaffold pole into and clamped a chain onto the nose and did some pulling. Not sure how much force this places though. 

I had a similar idea of building a 90 degree pulling arm and brace that slips onto the 3m longitudinal length and use a come along and chain/clamp to pull that way.  more technical to build but more versatile in directions it could pull in. Place the panel under tension then hammer and dolly damage.

8 hours ago, Namerow said:

Re the front bumper mount holes, I suggest you wait for corroboration from at least one additional owner

I agree that the bubble levels aren’t the most accurate method but I have to take what I get lol A second set of measurements would be fantastic is anyone out there is able to help?

2 hours ago, Patcon said:

Keep in mind that all of the repair work in this area needs to be done on the jig, not on the rotisserie

Yep that’s the plan Patcon, all structural work will take place on the jig. Rotisserie will be used for blasting and epoxy, removal of undercoating, some stitch weld finishing and painting the underside when the time comes. 

[Patcon]

Does your work area have a concrete floor? If so you could bolt the jig to the floor and use a hydraulic bottle jack under the lever. Then hammer and dolly

[240ZBUILTBYME]

1 hour ago, Patcon said:

Does your work area have a concrete floor? If so you could bolt the jig to the floor and use a hydraulic bottle jack under the lever. Then hammer and dolly

Yes it does sir, that’s a great idea! Definitely a good option 

[Namerow]

12 hours ago, 240ZBUILTBYME said:

I like the lever idea for its simplicity, however my front bolt hole needs to come up so may be less effective. As the car will lift before I get enough force on the panel I feel. 

Further to Patcon's suggestion, you could also consider sliding a next-side-up extension tube over the end of the longitudinal floor runner of your frame rig and then using that as a reaction structure (i.e. put the bottle jack between the extension piece and the lever arm).  Depends on how long the existing frame 'stub' is.  I don't think I'd try this unless that stub is at least 18" long (which your pictures suggest to be the case).   The reaction load (which would be tension, not compression) would be taken out of the vehicle structure through the front-most support point of your frame rig.  Right now, I believe that is at either the front crossmember location -- which is a good distance back from the rad bulkhead.  I'd like to see the reaction load being taken up further forward.  Maybe you could rig up a chain, looped over the lower part of the rad bulkhead and then anchored to the top of the new extension tube by way of a couple of (sturdy) welded-on eye-bolts.  Include turnbuckles in the two chain drops so that you can pre-tension the chain.

While considering how this 'adjustment' might take, it may help to stare at the following two pictures for a few minutes while asking yourself, 'What panels deformed during the collision event?' and then, 'How can I un-do that deformation?'.  The panel's main strength in the vertical bending plane comes from that long doubler panel (which has been removed by the owner in the top picture). It works with the main stamping to form a box section (which is sometimes referred to as the upper frame horn).  However, notice how that box section is weakened near the front by the big hole punched in the main panel to form the fresh air inlet for the car's cabin ventilation system.  I suspect that that's where the deformation happens in a front-end collision.  In fact, in the lower picture it almost looks like the outer wall of the doubler plate has been kinked.    For reference, I've added a third picture showing a pair of virgin OE doubler plates.

 

[Patcon]

Also this repair would be easier if you remove the doubler plate so you are not fighting the boxed section. You could remove the whole thing or just cut it far enough back to be past the damage. Then remove that portion. Then you can dolly both pieces inside and out. Weld back in with a butt seam and smooth them out. Also like Namerow suggested you could hold the car down closer to the front to reduce the stress on the frame rail. You could go on Ebay and order some frame clamps. I have an assortment that I use with come-alongs or chain binders for lighter damage work

[240ZBUILTBYME]

@Patcon @Namerow 

all great ideas, I wish I could get stuck into it already! 

my damage is as follows, lines indicate crumpled metal. Arrow indicates direction I need to pull which is why a pulling frame may be the way to go. 

I do also have provisions to build a frame that bolts into the sway bar mounts but this frame will only be 25mm or 1 inch tubing, but would still bring the force forward. 

yes I will be removing the doubler panel as you call it, namerow you are correct in saying it is the weak point and if you look at my photos you’ll see mine was folded where that dimple sits. I will be cutting and replacing that damaged section with the clean front cut I have.