Performance of I. C. engines at different compression ratios is an interesting characteristic. Keeping this in mind, we developed a variable compression petrol engine, which possess a variable ignition timing also. Thus, it presents a wide range of experiments, to evaluate the performance at various speeds, various compression ratios and various ignition timings. The range of compression ratio is 5.5 to 10 and range of ignition timing is 28 O BTDC to 10 O ATDC. The engine comes with rope brake or electrical dynamometer.