Key Specifications
-
Part Number: K666M855AP
-
Engine: 4G63
-
Bore Size: 85.50mm
-
Oversize: +0.020″
-
Compression Ratio: 9.5:1
-
Forged aluminum construction
⚠️ Requires proper machine work to match 85.50mm bore.
Product Overview:
– Wiseco Pistons Compatible With Mit-Subishi Evo – Hd2 Asymmetric Skirt – 4G63 Evo 4-9, Bore 3.366 (85.5Mm), Stroke 3.465 (88Mm), Rod Length 5.906 (150Mm), Compression Height 1.373 (34.875Mm), Dish -9.5Cc, Pin 22Mm, Set Of 4 Pistons
Product Info:
– Wiseco Mitsu Evo 4-9 4G63 Asymmetric Skirt Bore 85.50Mm – Size +.020 – Cr 9.5 Piston Set
Manufacturer Part Number:
– Part Number: K666m855ap
Why +.020 Overbore?
A +0.020” overbore:
-
Cleans up worn cylinder walls
-
Restores cylinder geometry
-
Supports fresh rebuilds
-
Improves ring sealing
Always measure block before selecting piston size.
Product Features:
– 2618 Aerospace Alloy For Superior Strength
– Hd2 Severe Duty Forging Available For Heavy Horsepower Applications
– Armorglide Skirt Coating Is A Standard Feature
– Armorplating Available On Select Applications
– Strutted Forging For Improvised Strength
– Pin 22Mm
– Performance Piston Ring Set Included
Product Specifications:
– Set Of 4 Piston
– Bore Size: 3.366
– Crankshaft Stroke: 3.465
– Rod Length: 5.906
– Piston Type: Dish
– Compression Height: 1.373
– Piston Material: Forged
– Wrist Pin Size: 22Mm
– Compressions Ratio: 9.5: 1
Why 9.5:1 Compression?
A 9.5:1 ratio provides:
-
Strong spool response
-
Good midrange torque
-
Better off-boost drivability
-
Compatible with moderate boost setups
Balanced for responsive turbo builds without sacrificing reliability.
Why Forged Wiseco Pistons?
Forged pistons offer:
-
Higher strength under boost
-
Better detonation resistance
-
Improved heat tolerance
-
Stronger ring lands
-
Higher RPM durability
On a 4G63 build, forged internals are foundational.
Ideal Applications
-
Street turbo 4G63 builds
-
Fresh engine rebuilds
-
Moderate to high boost setups
-
DSM and Evo applications
Pair with forged rods, ARP hardware, and proper tuning for best results.
Installation Notes
-
Machine block to 85.50mm precisely
-
Verify piston-to-wall clearance
-
Gap rings according to boost level
-
Balance rotating assembly
-
Follow proper break-in procedure
Because piston clearance isn’t “close enough” territory.
Important information
Legal Disclaimer
This product is an aftermarket product. It is not OEM and is neither manufactured nor sold by the vehicle manufacturer listed. We are not affiliated with the vehicle manufacturer.
Final Verdict
The Wiseco K666M855AP Piston Set (85.50mm +.020 / 9.5:1) is a strong foundation for rebuilt or performance 4G63 engines. Forged strength, balanced compression, and ready for boost.
Because if you’re building it once, build it properly.
There are no reviews yet.