What is the torque specification for engine bolts?
2 Answers
It is necessary to consult the vehicle's maintenance manual or owner's manual, and follow the manufacturer's specifications as the sole standard. For household passenger vehicles, the torque is generally 90-110N, which is approximately equivalent to a one-meter lever with 9-11 kilograms of force. Below is relevant information regarding automotive torque: 1. Definition: Automotive torque refers to the rotational force output from the crankshaft of the engine. Under a fixed power condition, it has an inverse relationship with engine speed—the faster the speed, the smaller the torque, and vice versa. This reflects the vehicle's load-bearing capacity within a certain range. The reciprocating motion of the piston in the cylinder performs a certain amount of work per cycle, measured in Newton meters. The work done per unit distance is torque; 2. Calculation: Torque × transmission gear ratio × final drive ratio × mechanical efficiency.
As an experienced mechanic, I've seen it all when it comes to engine bolts. There are many types: cylinder head bolts need to be tightened to over 100 Nm in a crisscross pattern in two stages; the oil pan drain plug requires less torque, just 20-50 Nm; spark plugs are even more delicate, usually around 30 Nm. Aluminum engines generally require 20-30% less torque than cast iron engines, and requirements differ completely between new Japanese cars and old German models. I recommend using a mechanical pointer-type torque wrench - the digital display ones have greater margin of error. Last time I encountered an owner who snapped a bolt while changing oil, eventually requiring engine casing disassembly to remove fragments. If unsure about parameters, check the owner's manual first. If unavailable, consult the brand's 4S shop to check their repair system. Even slight deviations in engine bolt torque can cause oil leaks or cylinder scoring - never rely on guesswork when tightening.
