Wiseco ArmorGlide 86mm Bore Pistons for K20A2/K20Z1/K20Z3

Wiseco ArmorGlide Forged Pistons - K20A2/K20Z1/K20Z3 (86mm Bore)

You're building an all-motor K20 and you need pistons that can handle 8,500 RPM and compression ratios high enough to make real power on pump gas or E85. Stock cast pistons crack under high RPM and high cylinder pressure. You're also dealing with piston slap on cold starts because the stock pistons have loose piston-to-wall clearances. Wiseco's ArmorGlide forged pistons are built specifically for high-compression K20 builds. These are 86mm bore pistons for K20A2, K20Z1, and K20Z3 engines. They're available in two compression ratios: 11.6:1 and 12.2:1. The 11.6:1 pistons are for street builds on 93 octane pump gas or conservative all-motor builds. The 12.2:1 pistons are for serious all-motor racing on E85 or race gas. Wiseco forges these pistons in-house from 2618 aluminum. They're stronger and lighter than cast pistons. The skirts are coated with ArmorGlide which reduces friction, quiets down piston slap, and lets you run tighter piston-to-wall clearances for better ring seal. Each set comes with four pistons, four wrist pins, four pin locks, and four ring sets. You're boring the block to 86mm, honing it, installing these pistons, and you're done.

Here's Why You Need Forged Pistons for High-Compression Builds

Stock K20 pistons are cast aluminum. Casting's a cheap way to make pistons but the material's not as strong as forged aluminum. Cast pistons are fine for stock engines making stock power at stock RPM. They're not fine for high-compression all-motor builds that rev to 8,500 RPM and make peak cylinder pressures of 1,200+ PSI. Cast pistons crack at the ring lands or the wrist pin bosses. The cracks propagate and eventually the piston breaks. You get a hole in the block and the engine's done. Wiseco forges these pistons from 2618 aluminum billet. Forging compresses the aluminum under extreme pressure which aligns the grain structure and makes the material way stronger than cast aluminum. A forged piston can handle higher cylinder pressures, higher RPM, and higher temperatures without cracking. If you're building an all-motor K20 with 11:1 or 12:1 compression and you're revving to 8,500 RPM, you need forged pistons. Stock pistons won't last.

11.6:1 vs. 12.2:1 Compression Ratio

Wiseco makes these pistons in two compression ratios. Here's when you'd run each one. The 11.6:1 pistons are for street builds on 93 octane pump gas or for conservative all-motor builds that see track use on pump gas or E85. With 11.6:1 compression on a K20, you're making around 220-230 whp with bolt-ons, cams, and a good tune. You can run 93 octane pump gas without detonation if your tune's dialed in correctly. You can also run E85 and make a bit more power (maybe 240-250 whp) because E85's octane rating is way higher than pump gas. The 12.2:1 pistons are for serious all-motor racing builds. With 12.2:1 compression, you're making 240-260 whp on E85 or race gas. You can't run pump gas with 12.2:1 compression. You'll detonate and destroy the engine. E85's the minimum fuel for 12.2:1. If you're running race gas (like VP C16 or Sunoco 260 GT), you can push the tune harder and make even more power. The 12.2:1 pistons are for race cars, time attack builds, and engines that get torn down regularly. If you're building a street car that sees occasional track use, stick with 11.6:1.

ArmorGlide Skirt Coating Reduces Friction and Piston Slap

Wiseco coats the piston skirts with ArmorGlide. That's a dry film lubricant coating that reduces friction between the piston and the cylinder wall. Lower friction means less parasitic drag and more power gets to the wheels instead of being lost to heat. ArmorGlide also lets you run tighter piston-to-wall clearances. Stock cast pistons need loose clearances (around 0.003-0.004 inch) because the pistons expand a lot when they get hot. Forged pistons with ArmorGlide can run tighter clearances (around 0.0015-0.002 inch) because the coating prevents scuffing during cold starts and the tighter fit gives you better ring seal. Better ring seal means less blowby, more cylinder pressure, and more power. Tighter clearances also reduce piston slap noise on cold starts. If you've ever heard a high-compression all-motor build with loose piston clearances, you know what piston slap sounds like. It's a loud knocking noise when the engine's cold that goes away once the pistons warm up and expand. ArmorGlide and tighter clearances quiet that down significantly.

Armor Plating on Ring Grooves and Wrist Pin Bores

Wiseco uses Armor Plating on the top of the piston and the wrist pin bores. That's a hard anodized coating that increases the hardness of the aluminum. The coating's bronze-colored so you can tell these are Armor Plated pistons just by looking at them. Armor Plating does a few things. It hardens the ring grooves so the piston rings don't wear into the grooves and cause blowby. High-RPM engines put a lot of side load on the piston rings and uncoated aluminum ring grooves wear out over time. Armor Plating prevents that. The coating also prevents micro-welding between the piston rings and the ring grooves. Micro-welding happens when the rings get hot and start to fuse to the aluminum. That causes the rings to stick and you lose ring seal. Armor Plating prevents micro-welding. The coating also resists carbon buildup on the piston crown and it protects against corrosion from detonation. If you're running E85 or you've got a tune that occasionally touches light detonation, Armor Plating gives you some insurance against piston damage.

Complex Dome Shape and Valve Pockets for K20 Head

Wiseco designs these pistons specifically for the K20 cylinder head. The dome shape's optimized for the K20 combustion chamber. The valve pockets are machined to clear the intake and exhaust valves with aggressive cam profiles. If you're running aftermarket cams with more lift and duration than stock, these pistons have the clearance you need. The piston crown's also textured. Wiseco machines a rough texture into the top of the piston to improve flame propagation. The texture creates turbulence in the combustion chamber which helps the air-fuel mixture burn more completely. Better combustion means more power and better fuel economy. The pistons also come with ring sets. Wiseco includes steel top rings with a nitride coating and a napier second ring. The top ring's designed to seal at high RPM and high cylinder pressure. The second ring's designed to control oil and prevent blowby.

What You Get

• Wiseco ArmorGlide forged pistons - 86mm bore (set of 4)
• Compression ratio: 11.6:1 or 12.2:1 (select when ordering)
• 2618 aluminum forgings (in-house forging process)
• ArmorGlide skirt coating (reduces friction, quiets piston slap)
• Armor Plating on piston crown and wrist pin bores (bronze-colored hard anodized coating)
• Complex dome shape optimized for K20 combustion chamber
• Valve pockets machined for clearance with aftermarket cams
• Textured piston crown for impro