Rust problem with front box sections

[Richard Williams]

I was dissapointed to find some serious corrosion in the undersides of the two box sections that form the engine mounting.The point was where the bolted cross member is at the level of the clutch when the engine is in place. Two questions .Is this a common site, I thought rear suspension mountings and front jacking points were the worst? . Next question has anyone made a repair in this area and was it with the engine in or out?

 

[malcolm]

That is an odd place for them to rust. It's more normal to see rust after those box sections go into the front floor. But I noticed my '68 car has patches under the front box sections so I guess it can happen.

The '68 car has patches only on the botom face of those box sections - the sides look OK, so hopefully that'll all that's wrong with your car. I would go about the repair without removing the engine as it's not in the way and is unlikely to catch fire while welding.

 

[Steve Hennessey]

Malcolm, I've seen rusting in this area quite a few times. It is caused by water being trapped between the thin outer skin and the thicker reinforcement plate inside.

The thin rusty outer skin needs to be cut away to leave good metal. This will expose the thicker plating inside which may also be rusty. Some more of the outer skin may need to be removed until it can be determined how much repair is needed to the inner plating. This needs to be repaired with 18 SWG (or metric equivalent) metal. Then use 20 or 22 SWG metal to repair the outer skin by seam welding around the edges and plug welding to the 18 SWG inner reinforcement. This can be a tricky job and needs to be done with a mig.

Once the chassis legs are determined to be rust free, they will need drilling along the top edge and waxoil liberally applied using an oil spray gun and approx 100psi pressure to prevent further rusting.

Steve

 

[Simon.AU]

I'd agree, it does seem to be a common problem, especially on the survivors in AUS (pre 1967 cars). The AUS spec cars have a poor road type front end with a triple skin under the front chassis rails, so the base of the rail is rarely rusted through. However the sides of the rail adjacent to the bolt on cross member can rust through, only problem is that the damage is usually well hidden by all the accumulated oil and road crud. It takes a clean and a probe with a screwdriver for investigation to take place.