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Superior Millennium Cylinder Complete Assemblies SL36006N-A20P Narrow Deck

Select Cylinders:
Single Cylinder4 Cylinder Kit6 Cylinder Kit


Complete New Millennium Cylinder Assemblies contain the following new parts: head, barrel, valves, valve seats, valve guides, piston, rings, gasket kit, seals, springs, rotocoils, and rocker shafts. The cylinders will not include piston pins or rocker arms.

#1 Aftermarket Cylinder in the World!

With well over 100,000 currently in service around the world and millions of flight hours behind them, Superior’s Millennium Cylinders® are without question, the most popular FAA-approved, PMA aftermarket cylinders in all of general aviation.

But Superior is not just the world’s #1 dedicated cylinder supplier we are also the leader in cylinder design and performance innovation.

Each Millennium Cylinder is an engineering and manufacturing masterpiece. From its advanced computer generated head fin configuration, to its 3-D port contour and increased wall thickness, to its advanced aluminum alloy heads and through hardened AMS 6382 steel barrel, Millennium Cylinder’s deliver performance and quality benefits far surpassing anything else in the air.

Looks great. Performs better.

Put any Millennium Cylinder side-by-side with any other OEM or aftermarket cylinder and the difference in quality, craftsmanship and attention to detail is strikingly obvious.

And while it looks really great, it performs even better. Millennium Cylinders resist cracking, run cooler, last longer and generally out perform the standard cylinders available from Lycoming, Continental or any other aftermarket supplier.

We’re so confident in the Millennium Cylinder’s performance that it’s covered by a full 25-month/TBO* (whichever comes first) warranty. It’s one of the best in the business.
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Features / Benefits

Advanced Aluminum Alloy Heads
Millennium cylinders are manufactured from the most advanced alloys available. That means their structural strength exceeds the latest aerospace industry requirements for air-cooled cylinder heads. In addition, our head castings meet, or exceed, the industry’s more stringent standards for porosity and shrinkage.

Increased Port Wall Thickness
The Millennium cylinder’s unique design also features increased port wall thickness to eliminate problems with premature warpage and cracking. In addition, the exhaust and intake ports are volumetrically matched to maximum output and performance.

Computer-generated Head Fin Configuration
Millennium cylinders feature new and advanced computer-generated head fin configuration that provides more consistent head fin thickness and spacing – that means they deliver more uniform heat transfer and fewer “hot” spots.

Improved Cooling
Millennium cylinders also have aerodynamically smoother surfaces to reduce wind resistance, which enables ambient air to more rapidly draw heat away. Bottom line: Millennium cylinders run cooler and cooler cylinders last longer.

Very high quality casting
Millennium cylinders perform better because they are made better. Our extremely high-quality castings create aerodynamically smoother surfaces to improve overall airflow and cooling.

Through hardened steel barrels
The barrel of each Millennium cylinder offers uniform hardness all the way through the steel walls allowing the barrel to provide even wear while withstanding extreme cylinder temperatures and pressures. This means Millennium cylinders typically reach and often exceed, recommended TBO times.

Ams6382 steel barrels
Millennium cylinders are manufactured with ams6382 steel barrels ensuring complete control of all critical manufacturing processes from the grain size of the steel to the elimination of both micro-impurities and defects in the alloy.

Advanced cylinder barrel choke
Our advanced manufacturing techniques also enable us to craft the Millennium cylinder’s barrel choke from 10 to 13 thousandths of an inch, allowing the rings and pistons to work more efficiently throughout the normal operating temperature range.

Volumetrically matched ports
The intake and exhaust ports on each Millennium cylinder are volumetrically matched for maximum output and performance.


Engine Configurations
HIO-360 -B1A
HO-360 -B1A, -B1B
IO-360 -B1A, -B1B
IO-540 -C1B5, -C1C5, -C2C, -C4A5, -C4B5, -C4B5D , -C4C5, -C4D5D, -D4A5, -D4B5, -D4C5, -N1A5
O-360 -A1A, -A1C, -A1D, -A2A, -A2D, -A2E, -A3A , -C2A, -C2C, -C2D
O-540 -A1A, -A1A5, -A1B5, -A1C5, -A1D, -A1D5, -A2B, -A3D5, -D1A5, -E1A, -E4A5, -E4B5, -E4B5D, -E4C5, -G1A5, -G2A5
TIO-540 -G1A


Parts per Assembly

  • 1 - Guide, Int. Valve (SL61681A)
  • 1 - Insert Intake Valve Seat (SL72057A)
  • 1 - Insert Exhaust Valve Seat (SL72058A)
  • 1 - Guide, Exhaust Valve (SL74230A)
  • 1 - Elbow (MS20823-8D)
  • 2 - Helicoil (MS9018-05/2-52)
  • 2 - Insert, Helicoil 1/8-27 Npt (SL-STD-1872)
  • 2 - Plug (MS49005-2)
  • 2 - Stud, 5/16 In Dia, Coarse Thrd (SL31C-12)
  • 1 - Stud (SL25C-9)
  • 4 - Bushing, Rocker, Shaft (SL66610)
  • 1 - Cylinder Stud (SL36006N-A1)
  • 1 - Cap (MS13998-3)
  • 2 - Key (MS13997-3)
  • 1 - Seat, Valve, Spring (SL10077)
  • 2 - Inner Valve Spring (SL11795)
  • 2 - Spring (SL11800)
  • 1 - Seat, Valve Spring (SL13323)
  • 1 - Seat, Valve Spring (SL16475)
  • 1 - Valve, Exhaust (Rotor Type) (SL19001A)
  • 1 - Valve, Int. (SL73938)
  • 2 - Key, Valve (SL60009)
  • 1 - Spring Seat (SL65441)
  • 1 - Lock Plate (SL12272)
  • 2 - Seal - Shroud Tube (SL18661)
  • 2 - O-Ring (SL70310)
  • 1 - Ring, Oil Seal, 4.84 Id X .04 (SL71481)
  • 1 - Gasket (SL71973)
  • 1 - Gasket (SL75906)
  • 1 - Shaft, Rocker Valve (SL13790A)
  • 2 - Thrust Button (SL12892)
  • 1 - Spring (SL14995)
  • 1 - 235/360/540 Valve Cover (SL61247)
  • 2 - Ring, Piston (SL74241A)
  • 1 - Ring, Oil Control (SL73857A)
  • 1 - Piston (SL75089A)
  • Frequently Purchased With
  • Customers Also Viewed


Norm P Verified Purchase


October 4, 2023

In stock, quick shipping, and a 25month warranty- this a no brainer. This is the 2nd I’ve had to install this year due to exhaust valve leakage on my 700hr o-360. Planning on replacing the remaining 2 for a complete millennium top end.

Jason S Verified Purchase


September 24, 2023


Deed P Verified Purchase


December 23, 2022

Cylinders are in good shape, received promptly but paper work is a mess. Non was received with the parts and efforts to get correct paperwork is still stalled

Robert U
May 5, 2018

Super disappointed. Just bolted one of these on, only to find out that Superior doesnt make them with a bayonet style CHT input. This seems to be the preferred method for modern EIS.

Chris P
March 16, 2023


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: What is the difference between this part number and Part # 08-11749?

The difference is W=Wide Deck and N=Narrow Deck. 08-11745 (SL36006N-A20P) is narrow deck and 08-11749 (SL36006W-A20P) is wide deck.

Q: Is this Superior Millennium cylinder high compression or low? Alternately, what is the compression ratio?

This is a high compression piston with a compression ratio of 8.5:1.

Q: What is the difference between the A20P and the A21P?

These are intended for different engine applications. Please review the engine applicability guide for the correct cylinder for your engine.

Q: Are the Pistons weight matched in a set of 4?

Yes, the sets are matched and shipped within a weight tolerance. If you require a specific tolerance or an exact match, please notate in the special instructions at the time of order.

Q: When we purchase this Superior cylinder do you issue an 8130 all together?

8130 forms can be furnished with new Superior cylinders. Please request at time of order.

Q: Does this cylinder come tapped for a CHT bayonet probe? One of the reviews says it does not and I find it hard to believe Superior would make a new cylinder without it.

Yes, these are tapped for a CHT.

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