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October 16, 2026, 12:58:37 PM

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[Oscar of Markoz]

I have recently Mini-tubbed my TF Cortina and thought I'd post it up as a tutorial for those that are thinking of doing the same thing.

First thing, if your going to do this mod, do yourself a favour and make the half tubs from scratch out of sheet metal. It'll be cleaner and easier. I've gone for the stock half tub, hence why Iam suggesting the new one. As it was more of a pain.

Tools you will need:
* Grinder - Cutting discs and flap discs
* Welder - Mig prefered
* Wire Wheel for drill or grinder
* Textor that writes on metal
* Rags, especially wet rags for welding
* Drill and drill bits for drilling through spot welds
* Leather welding gloves
* Safety Goggles
* hammer and doley
* Vice Grip clamps


Step 1:
Remove the backseat and backrest. Remove the seatbelts and parcel tray. Remove the rear scuff plates and rear door rubbers. Cover as much as you can with sheets and large rags. Especially windows and the front seats.
Mark out the half tubs with the textor. The is a seam that runs down the centre of the tub. Mark just to the inside of that seam. It just makes it easier and cleaner, as the cutting disc seems to find a groove to cut along. So this is where you'll be cutting. Measure from underneath the car, the distance from the end of the tub closest to the chassis rail, to the chassis rail. Its about 1-1/4 to 1-1/2 inches. Mark this rouchly along the top of that same space from inside the boot.
Make sure you move your taillight wires out of the way and cable tie them to the parcel tray so they are high.



Step 2:
Undo the bolts for the fuel line brackets and move the fuel lines out of the way and under the chassis rail. Then cable tie them to something like the trailing arm.



Step 3:
Drill out the spot welds on the brackets that are connected to the tub. There is one that is for your parcel tray and boot rods. Also 2 more from the cabin of the car, one for the parcel tray and one for the backseat brace. These will need modifying slightly later to allow for room so the tub can move over further towards the inside of the car.
Try not to pull on the bracket that holds the boot rods as they can let go.
I tryed to hook a rod back on using rope looped around it and the rope slipped, my hand moved up and scrapped along the half cut tub. This made a lovely cut needing 3 stitches on my ring finger and I still can't get my damn ring on cause the finger is so out of shape now. So if your doing this trick with the rope, wear the leather gloves!





Step 4:
Now you need to re-locate the fuel tank bracket on the RHS of the car. You need to jack up the fuel tank to support it and remove the hook bolt that goes onto the bracket. Then drill cut along the bottom of the bracket making the chassis rail an imaginary line. Once cut, drill out the spot welds and remove the upper half of the bracket. Once its removed, clean the area thorughly with the wire wheel. Give the bracket a slight hit with the hammer to push it further towards the centre of the car. Once the side lines up flush with the side of the chassis rail. Hold in place and tack weld on. Then full weld. Grind back flush with the chassis rail and coat with something like Etch Primer or Cold Gal. I hit it with the Cold Gal cause I had it lying around and Iam going to give the whole underbody a fresh coat of body deaner later anyway. I couldn't get a decent photo of the new bracket but you can see it in the last pics of the tub installed.
Put the hook bolt back on and then slowly lower the jack or stands that were supporting the fuel tank.



Step 5:
Get the drill and drill out some guide holes from under the car along the edge of the chassis rail. This will create some guide holes along the chassis rail that can be seen from inside the boot area to make things easier to cut the tub out. If you have the car on a rotisserie you could drill through the spot welds on the chassis rail that go into the floor and then cut just the floor from inside the boot. The advantage of this is that it would leave a lip on the chassis rail to be able to be bent up and over the floor and then welded, giving the rail more strength. But its very difficult work and take alot of time for very little gain.
Note, I have squared the corners of the tubs alittle more to allow more clearance when taller lo profile tires are used to get every last bit of clearance. The cortinas have a rather strange design for the front and rear end of the tubs which could be constrictive for big tires.
With the chassis rail, once the tub has been cut and removed, there is no lip on the chassis rail, so it leaves a gap between the rail and the boot floor. I tryed to weld the edges together to make a seam, your best to make a 1" by 1" right angle peice out of any sheet metal thats about the same thickness as the cars panels and welding that in. This will bind the chassis rail with the boot floor again. When I tryed to weld it, the edge of the chassis rail was so thin (because it had been cut along a bent edge) that it kept blowing out.





Step 6:
Cut the tub out with the grinder.





Step 7:
Then remove the lip off the tub. In the pic you can see the lip on and off. Use the grinder to get the spot welds off and then the grind smooth with the flap disc. Make sure you wire wheels the area as you'll be welding it back in afterwards. This is why its easier to make the tubs from scratch with fresh sheet metal.





Step 8:
Extend the tub the same distance as is needed to fill the gap, plus 10mm extra. The 10mm extra is used to overlap the existing half tub that is left in the car to make it easier to weld. I cut a strip of fresh sheet metal and allowed 10mm on either side of the strip.
Tacked it on in a few spots using vice grip clamps to hold in place.



Step 9:
Cut the tubs at the point where the ends start to curve in to much. Here is the amount i cut off each end. It started to make the tub too small so making these areas bigger and squarer would allow more room.




Step 10:
Tack the tubs back in place temporarily to make out templates for the new shoulders. Notice I overlap the lip extension over top of the existing half tub from inside the cabin.
Then mark out with craft cardboard and cut out templates. Transfer the templates onto sheet metal. Cut out slightly larger so you can trim and shape them as best you can
Wire wheel the tubs in all places that will be welded.





Step 11:
Once the templates are cut out of metal, try to shape them as best you can. I used some out piping I had and a hammer to make the curves etc. Its alittle tricky but not impossible. Then trial fit them to see where they need more shape or less. Anything you can't shape, once the tub is tacked in you can push against to pull out or hammer to pull in and then tack. I needed my brother to help me with this so while he pushed hard with the butt of a hammer, i tacked it and they hold well.
Full weld the tub extensions and then flap disc smooth. Its more important to get the underside of the tub smooth as that where your tires go and sharp edges here are a no-no.




Step 12:
Place you tubs in place and tack. Then full weld the seam along the chassis rail as again its needed grinding back and smoothing.
Spot weld every 1" the tub along the floor line from inside the boot area and stitch weld every 1" the half tub to the existins half tub from inside the boot area and cabin area.
Modify the brackets that attach to the tub. I just straightened them out 1st and then cut out the distance needed, rebent and welded them back on. The bracket that holds the boot rods is alittle easier, you can just straighten the bottom of it down straight. It just needs a small cut near the top where the bracket is bent give a slight angle. Once its cut here it bends straight really easily.
Coat with Cold Gal and then seam seal the new seams, under body the underside of the tub and your done.








The tire in the pic is a 265/18. Its only just wedged in there. Of course it up way to high, but it gives you an idea of how easy it'll take such a tire. Once the wheel arch is lipped it'll fit quite easily I reckon.

Note: I almost forgot. The exhaust will need slight modification at the bend before the rear muffler as it'll rub on the tires. Also the fuel tank seam/lip needs to be shaved slightly or it will rub on the tires also. Iam actually going to do something with the tank like use a different one or made just move it further towards the centre.




Next tutorial will be how to make a rotisserie and seam weld your chassis.

[CortinaD]

Nice & informative, thanks.

How long did it take you?

[Oscar of Markoz]

I can't remember now. I'll have to note that down for the other tutorials I make.
I was on and off for a fair bit due to my work situation. But I reckon non-stop say 8 hr days on it, it would have been maybe a week.

[chris adams]

nice ,we did quite a few mini tub setups in cortys generally the same way ,nice

[Oscar of Markoz]

Thanks mate. They look alot neater now. I've completely welded the tub to the boot floor and cabin floor. So its all sealed up now.

[TEV-08]

Excellant do it yourself I have measured this up already I was just unsure about where to start do'nt want to waste a good car. The part about the fuel tank I have got a torana tank and fuel filler that I am going to fit with the rear filler behind the number plate this will also give me a flat floor in the boot I will post some pics when I get time.

[memo351]

hey mate thats a top job have wanted to do that myself now i know how to go about it

[Oscar of Markoz]

http://www.fordaustraliaforums.com/forum/showthread.php?t=30156

Here you go if you want to follow up the build. You'll see what I did for a fuel tank and floor also.

[arms]

nice work does this also work on tc's