install 425 super rocket

1972madison · 08-13-2007, 05:51 PM

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 · 01-18-2008, 06:30 PM

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

2blu442 · 01-18-2008, 07:39 PM

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 · 01-18-2008, 08:02 PM

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

08-13-2007, 05:51 PM	#1 (permalink)
1972madison Member Join Date: Jun 2007 Posts: 38	install 425 super rocket 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. ????? __________________ -1972 442 with a 425 super rocket-

01-18-2008, 07:39 PM	#3 (permalink)
2blu442 Senior Member Join Date: Sep 2006 Location: Medford, Oregon Posts: 865	350 to 425 Swap 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 __________________ 1964 Cutlass Factory 4spd 1965 442 4spd 1967 442 Auto 1967 Cutlass Convertible 1968 442 Auto 1969 442 W30 Auto 1970 442 4spd 1971 Cutlass Flat Top Wagon 1973 Che*vy 3/4 Ton 454/TH400 Tow Vehicle Only the tow vehicle is finished!

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01-18-2008, 06:30 PM	#2 (permalink)
ijasond Senior Member Join Date: Feb 2007 Posts: 95	you'll need a 425 engine, a hoist, and some wrenches.

01-18-2008, 08:02 PM	#4 (permalink)
ijasond Senior Member Join Date: Feb 2007 Posts: 95	I'd say that advice was a bit more helpful than my sarcastic remarks.