90-99 Mitsubishi Eclipse Engine Internals
The 4G63 engine comes in two varieties, and they're distinguished by the number of bolts that hold the flywheel to the crank. The older six-bolt block had thicker rods and some other internal differences. The seven-bolt block replaced it sometime around mid-1992 build date.
If your car is a 90 or 91 and has its original motor, you have a six-bolt motor.
If your car is a '95 or newer turbo car, you have a seven-bolt motor.
92-93 cars are tricky, Mitsubishi used the seven bolt motor in the 1G chassis at this point. Mitsubishi supposedly produced the six bolts up until April, 1992. Telling the 6 bolt from the 7 bolt is tricky. Please verify either through a dealership or certified Mitsubishi mechanic which type you have before you order.