Miller Garage MGB Enthusiast

During a restoration of the car, options of how to finish the bottom of the car and giving it sound deading, rust protection, and finish appearance were considered. The selection was to apply a color tinted truckbed liner coating.

Tools and equipment needed for the task were an air compressor, pressure sand blaster, angle grinder with a twisted wire wheel, propane torch, hammer, chisel, paint scraper, wire brush, HVLP paint gun, 4 inch paint roller, paint brush, and Schutz spray gun.

Supplies used chemical paint stripper, sand, propane, masking tape, masking paper, seam sealer, epoxy primer, urethane reducer, and SEM Pro-Tex tintable bedliner coating. Always wear the safety equipment like gloves, eye, breathing, and hearing protection.

The bottom of the car was in various coatings with the replacement of the floor panels, sills, and other repairs. The first task was to remove the old coatings. A variety of methods were used with varying success. Sand blasting worked well and cleaned the surface. Some areas were more difficult because of the thickness of the original tar like undercoating. The one negative comment of sandblasting is the sand goes everywhere and there is more work created to clean after the blasting. Chemical striping also worked but was not as fast and did not clean as well as sand blasting. An angle grinder with a twisted wire wheel was used to clean what remained after the chemical stripping. The heat stripping method was using a propane torch or paint stripper gun. The undercoating was heated to melting point and scraped off the chassis. This method worked very fast and with additional cleaning using the angle grinder with a twisted wire wheel the chassis was very clean. The heat will damage the paint on the opposite side of the chassis. Applying the heat method is limited if the car is not being completely repainted. In colder climates, the undercoating becomes brittle at low temperatures and can be chipped off with a hammer and variety of chisels. Dry ice can be used to freeze the undercoating if you are in warm climate or warm season. It requires much effort whichever method or methods are used to remove the undercoating and properly prepare the chassis for painting.

With the undercoating removed the chassis is ready for painting. Follow the application directions for the bedliner product of your choice. The SEM brand truckbed liner required the chassis to be primed with an epoxy primer. The area to be painted was cleaned to bare metal, dust and dirt was removed, and wiped with a degreaser. The areas not to receive paint were covered and taped. The epoxy primer was applied with a HVLP gravity feed spray gun. Follow painting safety precautions as directed by the paint manufacturer such as proper ventilation, and using a respirator or external air supply.

The final step coating the bottom of the car with the color tinted bed liner was easy compared to the difficult removal of the tar undercoating and preparation work. The SEM product used in this application was a urethane based coating. The SEM Pro-Tex cures quickly and only mix an amount of coating that can be applied in the time allowed before curing. The mixture can be reduced or thinned using a compatable urethane reducer. Reducing is recommended for application with a paint brush and roller. The finished texture using a Schutz spray gun was thicker in appearance than the original tar undercoat. The uncured bedliner coating has the consistancy of pudding or yogert. The Schutz spray gun spits tiny globs of the coating under high air pressure. The coating hits the surface and leaves a lumpy texture finish. Using a paint brush to apply the mixture and a roller will produce a smoother texture finish closer to the original. The bedliner was applied to the bottom of the car, floors, frame rails, wheel arches, and under the front wings.