Calling all bodywork experts -- where to cut core support to weld in new front end

[Mark_BC]

I got my replacement core support to weld in and I'm wondering where to cut the front end to weld it in. The back end drivers side will be pretty straightforward, right at the firewall. But for the other end, I'm not sure. In the image below I show 2 locations where I can cut through the horizontal radiator supports and there is only a single layer of metal there which will make for cleaner welding.

But I am wondering if it's wise to cut and re-weld such small vulnerable pieces of metal. The alternative is to cut it at the passenger wheel well where my donor piece was cut, and weld it there.

Here are the advantages / disadvantages as I see it:

Cutting the radiator supports is easier and less metal to weld. It would be easier to line up the new piece exactly correct. However if I don't do good welds the small piece of metal might be a weak point. I could mitigate this by welding in some reinforcing pieces behind where you wouldn't see. On the other hand, the cut will be visible every time you open the hood so I'd have to blend it really well. I would practise on some scrap pieces.

Advantages of welding at the wheel well are that it is less visible, and there is more weld there to hold it together; not such a structurally vulnerable location. However, it will require pulling more stuff off the front end to put in the whole piece, and more painting.

Any welding experts out there with insight? I'll be using MIG.

 

[heat]

You just test-fitted the hood. Are the right fender and core support square?

 

[CodyRolph]

I have a similar project in process on an older toyota. Good thing is they built them with the same idea for structure ever since.

With that being said, I don't have to replace my inner fender pieces, only the front piece of sheet metal. So take this only as another idea on which way to do it.

Im planning on drilling all of the spot welds, then separating the very front piece of sheet metal from everything it is glued to. Leaving the inner fender structure on the truck, and welding all of the spot welds back together. Seam sealer on any exposed joints, then repainting.

If you don't like that idea, I would suggest cutting the inner fender, like you stated, there would be more structural integrity retained by not cutting the small pieces up front. Also welding on those small pieces will make them warp very easily. So they would be difficult to make as nice as factory again.

 

[Mark_BC]

You just test-fitted the hood. Are the right fender and core support square?

Yes

If you don't like that idea, I would suggest cutting the inner fender, like you stated, there would be more structural integrity retained by not cutting the small pieces up front. Also welding on those small pieces will make them warp very easily. So they would be difficult to make as nice as factory again.

Good point about the warping. I was thinking of going back to the wreckers and getting some scrap radiator support pieces and practising on the identical piece.

 

[phattyduck]

You should probably drill the spot welds and remove all of the 'rear' section of the passenger side of the replacement part. Leave as much known good stuff on the truck as possible.

-Charlie

 

[Joelzy]

yeah that^

i didn't do a great job of documenting this when i did it but you have to drill out all the spot welds. no cutting for just core support but may be different with stuff behind fender being replaced.

if you look at your replacement you'll be able to trace the spot welds from up where the perpendicular, under fender piece meets the core support, then down and around the headlight area and straight down. basically follows the inner fender well sheet metal

 

[Mark_BC]

You should probably drill the spot welds and remove all of the 'rear' section of the passenger side of the replacement part. Leave as much known good stuff on the truck as possible.

-Charlie

yeah that^

i didn't do a great job of documenting this when i did it but you have to drill out all the spot welds. no cutting for just core support but may be different with stuff behind fender being replaced.

if you look at your replacement you'll be able to trace the spot welds from up where the perpendicular, under fender piece meets the core support, then down and around the headlight area and straight down. basically follows the inner fender well sheet metal

Thanks, I guess that's the decision now. Do I drill out those spot welds on the passenger side where the core support meets the fender well (headlight area)? Then I'll have to re-weld those spot welds, and I don't think / know if I'm equipped to do that. Can I just tack weld each location where a spot weld used to be?

Or just cut the 2 horizontal pieces near the middle of the rad support and just do some weld lines to put in the new piece. This would be easier but harder to make look nice, and more likely to warp.

 

[phattyduck]

Can I just tack weld each location where a spot weld used to be?

Use a spot weld drill bit. The panels on the truck should not have a hole in them (or only a tiny hole). The 'new' core support will have holes. You then put little plug welds in place of the stock spot welds. It will look nearly stock if you do it right.

If you can find a spot weld seam on the other (driver's) side to work with, that would be better too. Otherwise, a lot of time/effort with spot / stitch welds and a grinder (and maybe filler) will work on the driver's side.

-Charlie

 

[Mark_BC]

Ok I think I get it. You drill the spot weld with the flat bit to remove the first layer of metal but keep the second layer intact other than the little pilot hole. I'm thinking that on the donor piece I'd drill out the spot welds on the layer from the piece not used (passenger wheel well), and similarly drill out the layer from the damaged piece to be removed from the vehicle (headlight piece), that way when the two good pieces come together (existing wheel well on truck + donor "headlight piece"), there will be complete metal there which will allow for an easy tack pseudo-spot weld? Also, I assume the spot welds aren't going to line up between the pieces so that means I may have more welds to do than are there now.


For the drivers side I'll have to cut and weld a new line through the wheel well. Otherwise I'd have to be fixing the spot weld removal on the firewall and I'm not keen about that. And the donor piece was cut just shy of the firewall so I dont have the material to for that anyways.

 

[phattyduck]

Also, I assume the spot welds aren't going to line up between the pieces so that means I may have more welds to do than are there now.

The factory spot welds were probably done via robot... they should line up perfectly. Just have holes in core support and grind the panel on the truck flat. Hit the insides with weld-through primer to keep rust at bay between the panels.

Lots of write-ups on this type of process out there...

S14 core support replacement how to - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

-Charlie

 

[Joelzy]

no idea on the back of the inner fenders but these might help a little on the spot welds.

[

this was once i had the factory core support off and shows where the spot welds are

I used every C clamp and vise grip i own to hold it in place where i wanted when tacking

being that the new support was solid and i had holes in most of the inside weld spots, i plug welded it from the back with a mig welder

 

[Houli]

I'll chime in here to re-enforce what has already been said. I replaced the core support in my 3rd gen a while back and it was pretty easy. I used a spot weld drill bit to drill all the way through the core support metal but left the fender well metal in place. This gives a good spot to weld to when installing the new one. I used a MIG welder to re-do the spot welds with no issues.

 

[Ifirefight]

You have quite a project there. I applaud you for tackling that. Use the whole core/radiator support all the way over to the right inner fender support. Like others said, drill the spot welds out, separate the metal. The firewall welds will be tough. Make sure you grind and have clean metal to weld to. Hammer and dolly everything so it fits right. Measure and re-measure and test fit all panels..hood,fenders etc. I you are off by a little bit, you will have a heck of a time ever getting it to line up.


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[Mark_BC]

Thanks everyone for the advice, I know how I'll do it now. I don't need to remove the passenger headlight section. I can remove the horizontal radiator supports from the headlight piece by drilling out spot welds. I can easily match it up the new piece exactly to where it was before using the front mount hole for the passenger fender.

And for the other end, in the wheel well, I'll have to cut and re-weld the piece in about an inch or so from the firewall. It will be about a foot of welding. I can match it up exactly by cutting the line through some of the holes in the metal so that I line the new piece up to complete the circle of the holes. I'll also have the mounting from the frame at the front driver's corner, and the fender mount holes.

So it doesn't look too difficult. I'm away for a week so won't get to it for a bit.

 

[Ifirefight]

The right/best way to do this is the way jolezy highlights in his picture. Do this on the passenger side and on the firewall. It’s hard to see from your pictures, but it doesn’t look like the “new” section was cut back far enough to the firewall..if that’s the case, then cut the old part off about an inch or so in front of the firewall, then overlap the new piece onto that.
Was this ever put on a frame machine to be pulled out prior to cutting the old parts off? If not, I’m afraid there could be more bent parts that might not look bent but are off by a bit. Does the driver door close good and line up with the rear door?
I’ll be watching, wishing you luck on this undertaking.
(PS, I did autobody heavy collision for 20 years)


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[UnlimitedT4R]

The right/best way to do this is the way jolezy highlights in his picture. Do this on the passenger side and on the firewall. It’s hard to see from your pictures, but it doesn’t look like the “new” section was cut back far enough to the firewall..if that’s the case, then cut the old part off about an inch or so in front of the firewall, then overlap the new piece onto that.
Was this ever put on a frame machine to be pulled out prior to cutting the old parts off? If not, I’m afraid there could be more bent parts that might not look bent but are off by a bit. Does the driver door close good and line up with the rear door?
I’ll be watching, wishing you luck on this undertaking.
(PS, I did autobody heavy collision for 20 years)


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Im late to this party due to being a noob on the forum, but I agree 100%. the damaged goods should be pulled/hammered back as close to the original position as possible before any sectioning. That being said, its unfortunate that there isn't a complete drivers side upper rail/apron to work with to make the job OE. As long as the damage didn't get into the firewall/hinge pillar and has enough good section to overlap things should work out. Mock up everything with clamps, get you cross and length measurements square, hang your fender, get the fender/door gap right, hang your hood with latch assy on the radiator support. have everything lined up and hood opening and shutting as it should before welding. take hood and fender back off and start welding. spray weld through primer on all mating surfaces prior to final assembly before welding and when finished welding use seam sealer. Good luck!

 

[Mark_BC]

Use the whole core/radiator support all the way over to the right inner fender support. Like others said, drill the spot welds out, separate the metal. The firewall welds will be tough. Make sure you grind and have clean metal to weld to. Hammer and dolly everything so it fits right. Measure and re-measure and test fit all panels..hood,fenders etc. I you are off by a little bit, you will have a heck of a time ever getting it to line up.

It’s hard to see from your pictures, but it doesn’t look like the “new” section was cut back far enough to the firewall..if that’s the case, then cut the old part off about an inch or so in front of the firewall, then overlap the new piece onto that.
Was this ever put on a frame machine to be pulled out prior to cutting the old parts off? If not, I’m afraid there could be more bent parts that might not look bent but are off by a bit. Does the driver door close good and line up with the rear door?

Im late to this party due to being a noob on the forum, but I agree 100%. the damaged goods should be pulled/hammered back as close to the original position as possible before any sectioning. That being said, its unfortunate that there isn't a complete drivers side upper rail/apron to work with to make the job OE. As long as the damage didn't get into the firewall/hinge pillar and has enough good section to overlap things should work out. Mock up everything with clamps, get you cross and length measurements square, hang your fender, get the fender/door gap right, hang your hood with latch assy on the radiator support. have everything lined up and hood opening and shutting as it should before welding. take hood and fender back off and start welding. spray weld through primer on all mating surfaces prior to final assembly before welding and when finished welding use seam sealer. Good luck!

A couple questions.

1) I'm away from the truck so I used Joelzy's photo. The passenger side "headlight" piece was undamaged. I'd like to try to not remove good material if possible, and removing that piece will require disassembling the A/C system because a pipe goes through it. So can't I just remove the spot welds circled in the photo below? That will take off the horizontal supports and leave the headlight piece on the truck which I know is good because it "lines up" (as well as a Certifit hood "lines up") with the new hood. I looked before and it looks pretty straightforward. The advantage of this is that it will be easy to line things up so they are in the right place.

2) Regarding the other end, you are suggesting that I overlap the sheets and weld that up. But on Arthur Tussik's channel I have seen him overlap the sheets and then run a grinder through both so that the cut is perfectly lined up. Then he welds that up so there is no seam. Can I do this, or is it not structurally strong? If I overlap then weld, I will have a raised line. Also, would I have to weld both lines of the overlap, one on each side?

As mentioned, I probably should have cut out the firewall too with the donor piece so I could take it all the way back to that. But on the other hand I think messing with the firewall would create some extra complications. The wheel bay isn't highly visible so I could get away with cutting a line and re-welding.

The metal is undamaged back at the firewall. Everything just folded up to the firewall. I test fit a driver's fender and it lines up well with the hood and front of the vehicle. The hood pillar is fine. The frame seems perfect except a bent lower control arm rear bracket which I'll deal with after I get the front end put back on and it's drivable.

 

[phattyduck]

2) Regarding the other end, you are suggesting that I overlap the sheets and weld that up. But on Arthur Tussik's channel I have seen him overlap the sheets and then run a grinder through both so that the cut is perfectly lined up. Then he welds that up so there is no seam. Can I do this, or is it not structurally strong? If I overlap then weld, I will have a raised line. Also, would I have to weld both lines of the overlap, one on each side?

He is a seriously talented professional. What works for him wont necessarily work for you (no offence). If you can take into account the cut off wheel kerf and get it 100% lined up, you could do it that way.

Overlapping sheet metal in the wheel well will be stronger and much easier. You will want to plug weld and tack on both sides. Seam seal, paint, and it will be fine and hidden. The overlapping metal (and ability to clamp) will be much more forgiving. You can consider using a body panel flanger to make it cleaner if you want, like this:

Panel Flanger Set Regular And Extra Wide

-Charlie

 

[Ifirefight]

A couple questions.



1) I'm away from the truck so I used Joelzy's photo. The passenger side "headlight" piece was undamaged. I'd like to try to not remove good material if possible, and removing that piece will require disassembling the A/C system because a pipe goes through it. So can't I just remove the spot welds circled in the photo below? That will take off the horizontal supports and leave the headlight piece on the truck which I know is good because it "lines up" (as well as a Certifit hood "lines up") with the new hood. I looked before and it looks pretty straightforward. The advantage of this is that it will be easy to line things up so they are in the right place.

2) Regarding the other end, you are suggesting that I overlap the sheets and weld that up. But on Arthur Tussik's channel I have seen him overlap the sheets and then run a grinder through both so that the cut is perfectly lined up. Then he welds that up so there is no seam. Can I do this, or is it not structurally strong? If I overlap then weld, I will have a raised line. Also, would I have to weld both lines of the overlap, one on each side?



As mentioned, I probably should have cut out the firewall too with the donor piece so I could take it all the way back to that. But on the other hand I think messing with the firewall would create some extra complications. The wheel bay isn't highly visible so I could get away with cutting a line and re-welding.



The metal is undamaged back at the firewall. Everything just folded up to the firewall. I test fit a driver's fender and it lines up well with the hood and front of the vehicle. The hood pillar is fine. The frame seems perfect except a bent lower control arm rear bracket which I'll deal with after I get the front end put back on and it's drivable.

For the passenger side, you can absolutely do it the way you stated, however my guess is there will be more welds to drill out that way. But either way will be fine, as long as you line it up exactly like it was.

2. I don’t know who Arthur Tussik is, but that method is fine for patching rust in a panel or something like that, but a butt weld on metal thinness of this gauge is not strong enough. You will have to overlap the pieces like I said. Yes there will be a line where you did this, but you can seam seal it afterwards. I can’t stress enough how important it is to have clean metal and tight fit before welding anything.


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[Ifirefight]

Also, would I have to weld both lines of the overlap, one on each side?.

No, no need to run a “bead” along the lines. Just spot weld, from both sides if possible.




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