Frame Engineering and Modification

The bare frame for the project came from a local British auto wrecker. It was sandblasted prior to working on it. All components to be mounted on the frame were acquired ahead of time to study their required dimensionality - the Corvette rear suspension, a 4 spd. muncie transmission, and an empty, cleaned and painted Chevy small block. The new frame components were fabricated and temporarily bolted together, and aligned. Donsco Offroad Vehicles, of Belmont, CA was commissioned to do the welding - my life is riding on those welds.

Stock Spitfire half-shafts cross over the frame. Vette independent rear suspension half-shafts cross underneath the frame. The 1964 Vette rear suspension is a complete assembly comprised of third member, transverse spring, half-shafts, brakes, and various other components. The rear portion of the stock Spitfire frame had to be modified to accept the Vette rear suspension which requires an overhead frame member on which to mount the differential. The rear portion of the stock frame was removed and the Vette rear suspension mounting modifications were added. The stock Spitfire frame is constructed in the shape of an hour-glass with a solid connector between the two frame rails. The connector is used for the rear transmission mount. The hour-glass design of the stock frame would be subject to high forces tending to warp the frame laterally. Therefore, two lengths of 2 inch x 2 inch x 1/8th inch square steel tubing were added that ran from the rear frame mods to the front of the frame modifying the 'hour-glass' frame to an 'H' frame with cross-member for stability under the extreme torque of a V8 engine. The resulting frame was very rigid and has worked flawlessly. The frame was then primed and painted - powder coating was not available. The engine, running gear, and suspension were mounted prior to placing the body on the frame to ensure the best alignment of components. The driveshaft was shortened appropriately.

The first diagram depicts a stock Spitfire frame in the hour-glass design. The second diagram shows a view of the overall modified frame in the 'H' layout. The third diagram shows the detail of the modifications necessary to mount the Vette independent rear suspension.

Stock Triumph Spitfire Frame, circa 1964



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