When my right hand drive Alpine was in bare metal I welded closed all of the left hand drive holes in the bulkhead that are normally covered with thin rubber grommets. I seam sealed all of the joins in the car body with flexible Tiger sealant and took a long time ensuring that everywhere where wires or cables passed through a panel it was sealed, initially with a grommet then with some butyl rubber to provide a TOTAL seal. I tightly sealed around things like the steering column, speedo cable, oil pressure pipe etc etc. Then I sound/heat proofed all along the gearbox tunnel underneath the car on the outside. Then I sound proofed the entire inside of the car. This included all of the floor, inside the rear wings, boot (trunk) floor, boot lid, inside the bonnet (hood), the inside bulkhead under the front scuttle and inside the doors.
Inside the hard top I used a square of hard rubber matting then covered that with a sheet of soft rubber faced with aluminium foil that covered the whole inside roof area.
I used a variety of different densities of sound proof material all over the car to ensure that I caught as many different frequencies as possible. In the footwell I used self adhesive rubber butyl sheets that you melt to the floor with a hair dryer. These are fantastic, they mould to the exact shape of the floor and set hard like a super thick coating of rubber paint. After the soundproofing was in place I sprayed creeping wax over it inside the doors, wings etc. The wax helps to dampen unwanted sounds as well as protecting from rust.
The end result is a VERY quiet Alpine. There are zero rattles or unwanted noises or smells. The engine bay is totally separated from the cabin as is the boot area.
I spent a lot of time doing this as we use the car regularly and want it to be a pleasurable experience.
Tim R
