Cometic StreetPro Top End Gasket Kit - 1991-1994 Nissan KA24DE | 90mm Bore, .051" MLS Head Gasket (C4514-051)

Rebuild your KA24DE's top end with confidence using the Cometic StreetPro top end gasket kit. Designed for the 1991-1994 Nissan KA24DE (S13 240SX), this complete kit includes all necessary gaskets and seals for a top end rebuild, centered around a .051" Multi-Layer Steel (MLS) cylinder head gasket in a 90mm bore — ideal for stock bore or mildly overbored KA24DE builds.

Key Features:

• Complete top end gasket kit
• .051" Multi-Layer Steel (MLS) cylinder head gasket
• 90mm bore diameter
• Cometic StreetPro quality materials throughout
• MLS, AFM, Aramid Fiber, and Armor Clad materials included
• All gaskets and seals needed for top end rebuild
• Fits 1991-1994 Nissan KA24DE (S13 240SX)
• Cometic Gasket quality and engineering

Kit Contents and Materials:

• Cylinder Head Gasket: .051" Multi-Layer Steel (MLS)
• Additional Gaskets: AFM (Advanced Fiber Material), Aramid Fiber, and Armor Clad materials as required
• Seals: All top end seals included
• Complete Kit: Everything needed for a full top end rebuild

Specifications:

• Brand: Cometic Gasket
• Part Number: C4514-051
• Kit Type: StreetPro Top End Gasket Kit
• Head Gasket Thickness: .051" (1.30mm)
• Head Gasket Type: Multi-Layer Steel (MLS)
• Bore Diameter: 90mm
• Weight: 2.4 lbs (complete kit)
• Barcode: 191070025311

Fitment Information:

• 1991-1994 Nissan 240SX S13 (KA24DE)
• Engine: KA24DE 2.4L DOHC inline-4
• Bore: 90mm (stock bore or up to 90mm overbore)
• Note: Verify your engine's bore diameter is 90mm before ordering
• Note: Stock KA24DE bore is 89mm - this kit is for engines bored to 90mm
• Note: Head surface finish must meet MLS gasket requirements before installation
• Installation: Professional engine building experience recommended

What's Included:

• Cometic MLS cylinder head gasket (.051" / 90mm bore)
• All additional top end gaskets (intake, exhaust, valve cover, etc.)
• All top end seals
• Note: Bottom end gaskets sold separately if needed
• Note: Head bolts/studs sold separately - replace at time of rebuild

Installation Notes:

• Professional engine building experience strongly recommended
• Deck surface must be properly prepared for MLS gasket - minimum Ra 60 microinch surface finish required
• Clean all mating surfaces thoroughly before installation
• Do not use sealant on MLS head gasket
• Replace head bolts or upgrade to ARP head studs at time of rebuild
• Torque head fasteners to manufacturer specifications in correct sequence
• Allow engine to reach operating temperature and re-torque if using head bolts (not required with ARP studs)

Cometic StreetPro Kit - What It Is:

The Cometic StreetPro series is designed for the budget-conscious engine builder who needs a complete, quality top end gasket kit without the premium price of Cometic's top-tier offerings. StreetPro kits include all the gaskets and seals needed for a complete top end rebuild, using quality materials appropriate for street and mild performance applications. The kit uses a mix of Cometic's proven gasket materials — MLS for the critical head gasket, and AFM (Advanced Fiber Material), Aramid Fiber, and Armor Clad for the remaining gaskets — providing the right material for each application in the kit.

Multi-Layer Steel (MLS) Head Gasket:

The .051" MLS head gasket is the centerpiece of this kit. Multi-Layer Steel head gaskets use multiple layers of embossed stainless steel to create a reliable, high-performance seal between the cylinder head and engine block. MLS gaskets provide superior sealing compared to traditional composite gaskets, particularly under the elevated temperatures and pressures of modified engines. The embossed layers create a spring-like sealing effect that maintains consistent clamping force across the gasket surface, even as the engine thermally cycles. MLS gaskets are the industry standard for performance engine builds and are required for any KA24DE build running elevated boost or compression.

.051" Thickness - Compression Ratio Considerations:

The .051" (1.30mm) head gasket thickness affects the engine's compression ratio. A thicker head gasket increases the combustion chamber volume, reducing compression ratio, while a thinner gasket reduces combustion chamber volume and increases compression. For a stock-displacement KA24DE, the .051" thickness provides a moderate compression ratio suitable for street use with pump fuel. If you are building a high-compression naturally aspirated KA24DE, a thinner gasket may be appropriate. For turbocharged builds, the .051" thickness helps manage compression ratio at elevated boost levels. Consult with your engine builder to determine the correct head gasket thickness for your specific build targets.

90mm Bore - Stock vs. Overbore:

The stock KA24DE bore diameter is 89mm. This kit is designed for engines that have been bored to 90mm — a common overbore for KA24DE rebuilds that allows the use of oversized pistons to restore cylinder dimensions after wear, or to increase displacement slightly. If your KA24DE has not been bored, verify your bore diameter before ordering. Using a head gasket with an incorrect bore diameter can result in the gasket overhanging into the combustion chamber or leaving the cylinder bore partially unsealed, both of which are serious engine-damaging conditions. Always measure your bore diameter before selecting a head gasket.

MLS Gasket Surface Finish Requirements:

MLS head gaskets require a properly prepared cylinder head and block deck surface to seal correctly. The surface finish must be smooth enough for the MLS layers to conform and seal — a minimum Ra 60 microinch (1.5 micron) finish is typically required, with Ra 30-60 microinch being ideal. Rough or damaged deck surfaces will not seal properly with an MLS gasket and can result in coolant or combustion gas leaks. If your KA24DE has been previously rebuilt or has a damaged head surface, have the head and block decks resurfaced by a machine shop before installing the Cometic MLS gasket. Do not use gasket sealant with MLS gaskets — they are designed to seal without sealant.

Complete Top End Rebuild:

When performing a top end rebuild on a KA24DE, replace all gaskets and seals in the kit simultaneously. Reusing old gaskets when replacing the head gasket is a false economy — the labour to access the top end is already done, and old gaskets are likely near the end of their service life. The StreetPro kit provides everything needed for a complete top end refresh, ensuring all sealing surfaces are renewed at the same time. Additionally, replace the head bolts (or upgrade to ARP head studs) at the time of rebuild — head bolts are torque-to-yield fasteners that should not be reused.

Why Cometic Gasket?

Cometic Gasket is one of the most respected names in performance engine gaskets, trusted by professional engine builders, race teams, and enthusiasts worldwide. Their MLS head gaskets are used in championship-winning race engines and high-power street builds across all motorsport disciplines. Cometic's StreetPro kits bring their quality materials and engineering to budget-conscious builders, providing reliable sealing for street and mild performance applications. Cometic's extensive coverage of Nissan applications, including the KA24DE, ensures their gaskets are engineered to the correct specifications.

Perfect For:

• 1991-1994 Nissan 240SX S13 KA24DE top end rebuilds (90mm bore)
• KA24DE builds requiring MLS head gasket for elevated boost or compression
• 240SX engine rebuilds needing a complete top end gasket kit
• Budget-conscious KA24DE builders wanting Cometic quality
• Any KA24DE build bored to 90mm needing a complete top end gasket set

Perfect For: 1991-1994 Nissan 240SX KA24DE engine builders seeking Cometic StreetPro top end gasket kit with .051" MLS head gasket for a 90mm bore rebuild.

Pro Tip: Upgrade to ARP head studs at the same time as the gasket kit — ARP studs provide more consistent clamping force than factory head bolts, don't need re-torquing after heat cycling, and are reusable for future rebuilds.

Complete Top End Kit: .051" MLS head gasket. 90mm bore. MLS, AFM, Aramid Fiber, and Armor Clad materials. Fits 1991-1994 KA24DE S13. Deck surface preparation required. Do not use sealant.

Rebuild your KA24DE's top end with Cometic StreetPro — .051" MLS head gasket, 90mm bore, complete kit, proven Cometic quality for the 240SX platform.