Project Overview: The goal of this engine build was to make the maximum power possible within the limits of vintage racing rules, which usually keep modifications and upgrades to a minimum and as close to original as possible. The customer also wanted to have an engine with good mid range torque.
Getting the maximum displacement possible out of the motor was the first thing we focused our energy on. We accomplished this by combining the block of a Mercedes 230 4-cylinder engine that has a 94-mm bore with the crankshaft from a Mercedes 220 engine, which has a 92.4-mm stroke. The combination of the block and crankshaft yielded a displacement of 2,566-cc. The block was rebuilt with forged racing pistons with a relatively high 10.25:1 compression ratio. The internal components were also dynamically balanced. To prevent oil starvation at high RPMs and around fast corners, special oil baffles were installed in the oil pan. An aluminum flywheel with a Tilton racing clutch finished off the engine.
The 190SL cylinder head was flow tested both with and without the intake manifold and carburetor installed. This information was used in our engine simulation program to help determine camshaft profiles for the intake and exhaust systems. Additionally, all of the valves, seats, guides and valve train parts were replaced with brand new items. Intake port dividers were installed for better airflow and the head itself was ported for better air flow.
After careful assembly, the engine was installed on a DTS dyno and carefully broken in before we could begin running it under load at higher RPMs. After that, several dyno runs were performed in order to find the best combination of carburetor tuning and ignition advance that would produce the most possible horsepower and torque.
The result was an impressive 165-hp and 175 lb-ft of torque. This is a significant gain over the stock power rating, which is 105-hp and 105 lb-ft of torque.
Once it was installed back in the car, the engine raced successfully for many seasons in local vintage races, performing very well along the way.