Front chassis rail repair

Front chassis rail repair

As you may have seen in my last post, one of the worst horrors still lurking beneath my car is this front chassis (frame) rail on the offside corner, so I decided to tackle that whilst I await panels for the other areas. As I said in that post, if you’re thinking of buying an MGB and see rot like this in such a difficult and important area, my advice would be to run away and find a better one… but I’m a little bit too invested here, so let’s see what we make of it.

First job was to – almost literally – “rip off the band-aid”. Not one of my finest pieces of work, this beautiful patch is covering the rot in 3 separate sections of the body, and not even particularly well – you can see on the left there are still other areas of rust that were not addressed before (or have popped up in the intervening years).

A slightly closer view with the patch cut off. The sheared-off bolt was one of the bolts for the additional side support brackets for the front rubber bumper. I’m obviously cutting this section out, but I’ve decided not to refit these brackets, so will not be welding in new captive nuts here. They were deleted by the factory from later rubber bumper cars anyway, so I don’t think I’m losing much by not refitting them, except a bit of weight and a potential future rust trap.

I just carried on cutting until I got to good shiny metal on all sides! There had been another smaller patch here on the bottom of the rail, and also one of the anti-roll bar bracket bolts had sheared too and been badly re-drilled at some point in the past, so I cut that whole section out to replace properly. The other two sheared bolts on the left were for the undertray which was fitted to rubber bumper cars, I managed to drill them out and re-tap them.

By the time I’d finished cutting, the hole in the side of the main rail was now almost 12 inches long. It’s a bit of a tricky section to recreate, but through comparing it closely to the solid equivalent section on the other side, and some careful cardboard templating, I managed to get a pretty good reproduction made out of the correct guage steel. I painted the inside face of it as usual to give it a fighting chance of surviving.

Tacked into place, things are starting to come together. I’d already replaced the front six inches or so of the horizontal ‘wedge’ section as well, and also repaired the hole on the bottom of the rail and welded in a new captive nut for the ARB at this point.

After fully welding in, that was all ground back flat, and then I just needed to make this one final repair section to the inner wing panel to finish the job.

Ground back again, and then I wire brushed and Kurust-ed the surrounding areas, before applying a couple of coats of etch primer. Pretty pleased to have ticked that one off – once seam-sealed, stone-chipped and painted later on, this should look as good as new.

Leave a Reply

%d bloggers like this: