Installation of TC Seats, Sliding Rails, and Associated Hardware

One of the standard questions when a TC is been restored is, “Where do I drill the holes to secure the seats? There have been a number of writings and numbers thrown around on seat placement. However, through the years new seats, new holes, new floorboards, aftermarket seat rails, and rebuilt tubs have all changed dimensions whether 1/8” or a ½” from the factory equipment. You need to fit the seat for your car only with your new or replacement parts. The following explains seat originality and details a successful “refit” of the seats of TC7670 EXU.


The seat bases were made of ash wood with an early and late style. The early had round holes in the base and the later had elongated slots to let the air pass through upon compression. When finished, the openings should be covered with a course fabric from within the seat and the wood edges of the holes and wood bottoms should be painted flat black to give it a finished look. Also, an upholstery tape will cover the finished edge of material to wood. The original seat cushion said “DUNLOPILLO LATEX FOAM CUSHIONING, MADE IN ENGLAND, P36A/B”. (The A or B indicated which side/part # for the pillow). The cushion had square open chambers in the bottom of the dense spongy latex bottom. (Remarkably, the original cushions from TC7670 were in such good shape that they were reinstalled during its restoration as part of the effort to make it as original as possible as it came from the factory, so these will be a time capsule for the next restoration).

The seat backs have a plywood backboard with a set of springs fastened to it. The original coil springs were anchored to a frame made up of very heavy steel wire about 1/8” diameter. After market seat-back spring sets went to a framework consisting of strapped steel, providing a stronger base. The seat back also had holes to release air and should havethe wood edges painted the same as the seat bottoms.

Original seat back upholstery was finished using black cut nails (tacks) on the back of the seat. One distinct feature of the TC is the ribbed upholstery on both the bottoms and the back. There are 2 different methods of forming this pleat. The first is to take batting in between 2 layers of material and stitch together. The second is to stitch the 2 layers together and then butt a strip of batting and then repeat the process for each pleat. The original process used the latter method which gives a “puffy” type look to the seat and a more pleasing dimension to the eye. This may be a consideration for your restoration and selection of your vendor. Caution:Do not install any hardware on the back of the seat back until the seat bases are sited and placed.

Seat rails:

Original seat rails can be identified by the 3 screw holes in the floor mount tab. Some aftermarket rails only have 2 holes to secure the rails to the floorboards. The rails were cad plated (satin silver color) with the exception of the adjustment handle which was polished chrome. Even rusted seat rail can be resurrected to like new condition. Simply send the base rails and the non-chromed rail to the cad plater with all your nuts and bolts to get freshened for your restoration.

Then send the rail with the adjustment handle to the chrome plater and tell him to polish the handle only.

The seat rails are fastened to the bottom of the seat by 12 slotted flat head screws, screwed into T nuts in the seat bottoms. If you don’t have the original screws then you can use 10-24 screws from the local hardware. Some replacement seats have 10-32 threaded T nuts so select your screws accordingly. Unfortunately, the modern screw heads may be a little too large but you can trim the heads down on the grinder to a diameter to fit the rail itself. When installing the seat rails keep in mind that the adjustment handle goes to the outside of the car for each seat. After the rails are fastened to the bottom of the seat then slide the seat hinge rails into place on the seat bottoms.

Seat Installation:Where do I anchor the seat rails to the floorboards? There is no exact answer but there is a solution.

Adjust the seat in a notch that will let you move forward a couple of notches after installed. (This will allow your 16 year old son to drive the TC on his first date or to the prom.)

Place the seat bottom with rail attached in the car. Position and adjust the seat to parallel the tunnel. Then move it as close to the tunnel as possible which will allow only enough space for the thickness of the carpet over the tunnel. This would be about ¼ – 3/8” spacing.

  • Next move the seat towards the rear of the car while holding the seat back hinge parallel to the deck lid riser. Stop when the seat back hinge approaches the starting handle clips with ¼” to spare. If you are tall, and need extra leg room then you may consider removing the starting handle clips and repeat this step with a ¼” clearance to the riser only.

  • Check the clearance between the seat and the outside of the car. You should have about 1 ¼” spacing and the outside of the seat should parallel the outside of the car.

  • When satisfied with the clearances for these 3 sides, site and drill your holes for the rails to the floorboard and repeat the process for the other seat. Original fasteners where #8 x ½” slotted countersunk wood screws but through the years many of these have been replaced by other fasteners because the WS have pulled out of the floorboards. A suitablealternative is using #10 machine screws with a T nut under the floorboard.

  • Once the seat rails and bottoms are secure then it is time to fasten the hinge sleeves to the back of the seat. Some words of caution:Sometimes the seat hinges are not symmetrically installed per set. Therefore, measure the center of the hinge sleeve from the center of the tunnel and then site the same measurement on the back of the seat from the center of the back seat tunnel scallop. Install the bottom of the sleeve tangent to the bottom of the seat back. (This assumes that the tunnel was installed at the longitudinal center of the car, which you should also check). Use a #6 x ¾” slotted round head wood screw for the sleeves except for the bottom 2 screws and then use a shorter 3/8” long screw due to the reduced thickness

  • Next site the seat back adjustment brackets by first holding them in place with the wing nut to the wheel arch bracket. Make sure the washer/spacer is installed between the 2 brackets. Now let the seat rest against the brackets to determine the correct placement of screws into the seat back. Use tape to outline the perimeter of the bracket instead of marking up your new upholstery. When satisfied, position the tonneau bar with its top tangent to the top of the upholstery on the seat back. The bottom screw holes of the tonneau bar should be no higher than level with the top holes of the adjustment bracket or within ½” (see photo on page 18). Fasten brackets and tonneau bar to the seat back using #8 x 1” slotted oval head wood screws.

  • Finally, slide the seat back hinge sleeves onto the seat hinges and check the final fit.

Showing positioning of tonneau bar fixing relative to adjustment brackets

There may be other techniques or tips or suggestions which are always welcome. Please provide comment to Doug(at)

Doug Pelton

Doug Pelton, Proprietor
Mesa, Arizona, USA