well, typical combustion pressure is 1200psi, you if you have a 3" piston, pi R squared says area is 7.06 square inches. so 1200psi times 7 square inches is 8482 pounds... so, divide that weight, by your weight ~175 or so pounds and you would need a breaker bar 48 feet long to exert normal opperating pressure on the cylinder...
Edit:
Yes I know my math is completely wrong, thinking that 8482 ft-lbs is equal to 8482 lbs of force in the cylinder, but the fact is still the same, try to generate 1200 psi on your engine with a breaker bar. It isn't going to happen...