Hello Malc,
For years I rallied a 1968 Mercedes (W114) sedan with a W113 (280-SL) engine which I installed and modified. I ran it in the SCCA Pro Rally Series some of which were FIA events. Saving weight is a big advantage. Lightening up the car will increase its performance and durability. No major modifications were made to the engine. I did port and polish the cylinder head ports, which made a slightly noticable increase in power at high rpms.
A super heavy duty skid plate is critical. A four speed transmission was used with a full race metal clutch disc and double sprung pressure plate. The ignition was standard but the electronic units of today would be better. We used the original plastic covers for the distributor, coil and ignition points to help keep everything waterproof. Only the rear muffler was used to save weight, it also sounded great. I installed a 4:08 differential for acceleration. We also welded the rear differential solid for better traction on those wet slippery forest roads. A posi-traction rear diff. was available if you could find one.
I used only an electric radiator fan and removed the engine fan to conserve power. Other minor changes were heavy duty Bilstien shocks, heavier duty motor mounts (from MB V-8), alloy wheels, lighter Recaro seats, lightened body panels (fiberglass), factory trunk spoiler (500-SL) etc. The battery was relocated under where the back seat once was, for better weight distribution. Of coarse this type of rallying did require a full roll cage (used on several occassions) fire suits, etc. I added a fuel pressure guage, an oil temperature guage, vaccuum gauge, and volt gauge to the dash.
Navigational equipment was a Halda Twinmaster and Speedpilot, although computerized equipment was beginning to be used by the factory sponsored teams. The car would do 0 to 60mph in six seconds flat. It was very durable and competative. Lighting was critical, since most US performance rallies are held at night. We used higher voltage bulbs in the regular headlights and added two Hella flood lights pointed outward for cornering, also added two spotlights for long range one being a "pencil beam" with a range of nearly two miles. I forgot to mention we did install a larger Bosch alternator also.
I know you do not plan to run these stage rallies, but some of these preparations may be useful to you. Good luck.
Joe Alexander
Blacklick, Ohio
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