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 you have a 95-99 non-turbo DSM, this information does not apply. There is no six-bolt/seven-bolt distinction on the 420A motor. The same holds if you have a 1.8 SOHC motor.
But if you have a 2.0 DOHC 4G63 motor, read on...
If your car is a 90 or 91 and has its original motor, you have a six-bolt motor.
If you car is a '95 or newer turbo car, you have a seven-bolt motor.
If it's a 92-94, or if your motor might not be the original, you can follow the link below to figure out which motor is in your car. Thanks to Tom Stangl of VFAQ.com for maintaining that wonderful web site.
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