Swap an Evo 9 Cylinder Head onto an Evo 8 Short Block
Understanding the Evo 8 and Evo 9 Engine Differences
The Mitsubishi Evolution series, commonly referred to as just "Evos", feature high performance turbocharged engines. The Evo 8 came equipped with the renowned 4G63 engine, a 2.0L turbocharged powerplant renown for its tuning potential. The Evo 9 received an upgraded engine featuring MIVEC variable valve timing, dubbed the 4G63T MIVEC.
This upgrade brought more power, torque, and improved efficiency. Many Evo 8 owners have sought to swap the Evo 9 head onto their Evo 8 short blocks for these benefits. However, there are some important differences to understand first.
Crankshaft Differences
While the Evo 8 and Evo 9 blocks share the same 81mm bore and 88mm stroke, their crankshafts differ. The Evo 9 received a revised crank design to work with the upgraded head and MIVEC system. Therefore, the Evo 9's crank must be used for head swap projects.
MIVEC System Components
The Evo 9 cylinder head contains the valve components and camshafts to operate the MIVEC variable valve timing system. This means extra oil passages for the MIVEC solenoids must line up. Using the proper Evo 9 timing belt tensioner and oil control valves is critical.
Gathering The Necessary Evo Parts
For DIY mechanics tackling an Evo 8 and 9 head swap, gathering the necessary components takes careful planning. At minimum, you need the complete Evo 9 cylinder head assembly, intake manifold, fuel rail, cams, valvetrain, timing belt tensioner, crank pulley, engine sensors, and crankshaft.
Cylinder Head Considerations
Having the entire Evo 9 head assembly eliminates guesswork for matching MIVEC-related components. Inspect all mating surfaces for damage or wear first. Valve stem seals tend to fail on these engines, so replacing them may be necessary depending on mileage and prior maintenance.
Intake Manifold and Fuel System
The Evo 9 intake must be used to line up with the upgraded head. Fuel injectors, fuel rail, and other lines may also differ from Evo 8 equipment. Using all Evo 9 fuel system components avoids mismatches or leaks.
Performing the Cylinder Head Swap
With all the necessary Evo engine components acquired, it’s time to tackle this upgrade project. As with any major engine work, expect this to take a full weekend even for experienced wrenchers. Having an extra set of hands helps considerably as well.
Step-byStep Head Removal and Installation
Carefully disconnect sensors, fuel lines, intake piping and wiring before unbolting the head. With the valve cover off, cylinder head bolts can then be methodically loosened in sequence and removed. Note the locations of all sensors before removal.
Thoroughly clean the engine block’s mating surface to remove any debris or old gasket material. Lower the upgraded Evo 9 head into place, making sure alignment dowels properly line up.
Thread head bolts by hand several turns before final torqueing down to factory spec in the proper sequence. Triple check all clearance fits before connecting the valvetrain, sensors and cam gears.
Finishing Touches
With the upgraded head torque down and cam timing set, reconnect all fuel system components, intake piping, sensors and wiring. Use new seals/gaskets as needed to prevent vacuum or oil leaks.
Finish by reinstalling the valve cover and accessory components before attempting to fire up the engine. Check for leak downs or odd sensor readings that could indicate problems with the swap.
Properly Tuning the Evo 8 with Evo 9 Head
While this head swap unlocks more performance potential, custom ECU tuning will be required to optimize drivability. The Evo’s sophisticated AWD drivetrain depends heavily on proper engine tuning.
An experienced performance shop with a 4G63T MIVEC dyno tune is highly recommended over off-the-shelf maps. Custom tunes properly tailor timing, fuel maps, boost control and other parameters.
With custom tuning dialed in alongside upgraded injectors, intercoolers and exhaust work, Evo 8 owners can reliably achieve over 400 horsepower from this head swap project.
FAQs
Do I need to upgrade the Evo 8 fuel injectors?
Yes, upgrading to larger Evo 9 fuel injectors capable of handling more power is highly recommended. The OEM Evo 8 injectors will max out quickly with the new head and proper ECU tuning.
What are the key sensors to replace from the Evo 9?
The primary sensors to use from the Evo 9 include the cam position sensor, crank position sensor, manifold absolute pressure (MAP) sensor, mass air flow (MAF) sensor, and knock sensor.
Will my Evo 8 transmission be ok with the power increase?
The stock Evo 8 transmission should hold up fine to moderate power levels around 400hp. If planning much higher output, upgrading internal transmission components is recommended.
Can I install the head myself or do I need a shop?
Ambitious do-it-yourselfers can tackle this swap if they have experience with engine teardown/reassembly. However, having an experienced Mitsubishi performance shop handle the work can give peace of mind.
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