Technical how-to Archives | New Zealand Classic Car

Coaching from the bench: Casting plastic knobs and rubber parts

16 July, 2026

Casting rubber items is simple if you have a good original to work with. The item doesn’t have to be perfect. You can use plasticine to smooth out cracks, and you can even make whole prototypes out of low-fire modelling clay available from craft stores if you need to. Prototypes can also be made of wood or metal.
You will need mould dams to contain the liquid urethane moulding solution until it cures. You can build boxes out of strips of wood, but I have found that small plastic boxes and bowls such as those you would use for leftovers in your fridge work well if you spray them with a mould release agent.
Temperature is important to the chemical processes involved, so work in an area that can be maintained at around 20 degrees. You will also need adequate ventilation because the fumes can be dangerous to breathe. And you will want to wear latex gloves to protect your hands.

Polishing to perfection

26 February, 2026

The secret to a show-stopping finish is colour sanding, no matter which paint system you use. Even a good painter, no matter how experienced or talented — like my mate Bruce Haye, CEO at Ace Panel and Paint in Whitianga — can’t shoot to a perfect mirror finish. To get that level of perfection, you need to colour sand.
It used to be called ‘rubbing out’ or ‘cutting’, and it was done with pastes that came in cans. They worked — sort of — but the compounds really just rounded off imperfections instead of eliminating them, and they removed a lot of paint in the process. But now your new finish can be made flawless, thanks to microfine sandpapers that come in 1000, 1500, 2000, and even 2500 grit ranges, and Farecla G3 polish — available from automotive paint suppliers.

Blueprinting basics

3 October, 2025

You occasionally hear petrol heads tossing around the term ‘blueprinting’ when referring to an engine they have assembled, and have sometimes altered significantly. What they are probably trying to say is that their engine was carefully machined to optimum tolerances and balanced — probably for racing. But that isn’t what the term meant originally. You see, in the 1950s, when US stock car race cars really had to be stock, the racing teams would go to the factories and rummage through the parts bins until they found components that were closest in tolerance to the original blueprint developed by the engine’s designers.