1972madison

i currently have a 1972 350 rocket in my 72 cutlass and what will i need to change the motor to a 425 super rocket. ?????

ijasond

you'll need a 425 engine, a hoist, and some wrenches.

2blu442

I agree it's an easy swap, but a couple things to watch out for. Use the rubber 350 engine mounts with the 425 or change both the rubber mounts and the metal pads that are bolted to the frame crossmember to 455 parts. Either will work, just don't mix the small block/big block rubber mounts and metal pads. Then the exhaust, the small block manifolds will bolt up but not breath as well as big block. I believe the ideal would be to get a set of the W/Z exhaust manifolds used on 1969-72 big block cars or the X/Z manifolds used in the 73-74ish. These are the dual exhaust manifolds with dividers cast inside. You could use headers but I've found them to be a headache and more often than not needed to "modify" them with a ball peen hammer to make everything fit. Keep all the pullys from your 350 and use the 350 water pump and power steering pump. The pullys will swap between small and big block engines for the 1964-72 and beyond 330 to 455 engines, but try and keep a matched set or you may have trouble getting the belts to line up. Then I would use the 350 fan and fan shroud. I don't remember the years, but some have 19" across fans and some used 19 1/2" fans. On a project in the past I pulled my hair out trying to figure out why the fan hit the shroud! The engine to trannie bolts are the same, but the flexplate or flywheel has a different bolt pattern where it attaches to the crank, be sure you use the one from the 425. That's all I can think of at the moment, the nice thing about this vintage of Oldsmobile engines is that many parts will interchange between the small and big blocks, and the lower part of the engine blocks are the same. The big block (400,425,455) have taller deck heights, then the intake is wider. When you start turning wrenches if any questions come up post them as many people on this site have made similar swaps before. John

ijasond

I'd say that advice was a bit more helpful than my sarcastic remarks.