TOMEI ENG O H KIT FULL BL5 BP5 93.5-1.5 FOR SUBARU IMPREZA WRX STI EJ20 1964493151

 

TOMEI ENG O H KIT FULL BL5 BP5 93.5-1.5 FOR SUBARU IMPREZA WRX STI EJ20 1964493151

The TOMEI ENGINE O/H KIT Full for EJ20 BL5/BP5, 93.5 mm bore × 1.5 mm head-gasket thickness, P/N 1964493151 is essentially a comprehensive engine-rebuild gasket/sealing package, rather than a horsepower-producing engine kit. 

TOMEI lists it specifically for the EJ20 used in the Subaru Legacy B4 BL5 and Legacy Touring Wagon BP5. 

🔧 What the kit contains

According to TOMEI, the Full Kit combines:

• TOMEI metal head gasket
• Timing belt
• Timing-belt guide
• Oil filler cap
• Various gaskets and seals required during an engine overhaul
• Full-kit components that are not included in the cheaper pulley-less version 

The important specification is:

Specification	1964493151
Engine	Subaru EJ20
Application	BL5 / BP5
Kit	Full O/H Kit
Head-gasket bore	93.5 mm
Head-gasket thickness	1.5 mm
Part number	1964493151
Current TOMEI list price	¥198,000 incl. tax
Kit weight	~6.4 kg

TOMEI currently lists the 1.5-mm version alongside 0.7, 1.0, 1.2 and 1.8-mm alternatives. 

🧠 Why the 1.5-mm gasket matters

The 1.5 mm specification isn’t simply “thicker = stronger.” Head-gasket thickness affects the EJ20’s assembled combustion-chamber geometry and compression ratio.

Conceptually:

Thicker gasket → greater piston-to-head clearance → slightly larger combustion volume → lower compression ratio

while:

Thinner gasket → smaller clearance → slightly smaller combustion volume → higher compression ratio

So the 1.5-mm gasket should be selected according to the actual piston, block/head machining and desired compression ratio, rather than simply choosing it because the engine is modified.

🏁 Why the Full Kit is attractive for an EJ20 rebuild

The clever part of this package is that TOMEI isn’t only supplying a head gasket. It packages many of the consumables that are normally replaced when an EJ20 is opened up.

Think of the rebuild as:

EJ20 teardown → machining/inspection → new sealing system → timing system renewal → reassembly

The kit helps eliminate the situation where a rebuilt engine receives fresh internal components but retains a collection of old seals and timing components.

TOMEI describes the product specifically as a combination of its metal head gasket, timing belt, belt guide and oil filler cap together with the gasket/seal set required for an overhaul. 

⚙️ Full Kit vs Pulley-Less Kit

This is an important distinction:

Full Kit — 1964493151
→ includes the additional pulley-related components

Pulley-Less — 1964493152
→ same 93.5 × 1.5 mm gasket specification, but omits the pulley components.

🔬 Engineering interpretation

For a serious EJ20 rebuild, I’d classify this as:

OEM refresh kit: ★★★★☆
Performance potential: ★★★☆☆
Reliability contribution: ★★★★★
Track-build usefulness: ★★★★★
Direct horsepower gain: ★☆☆☆☆

The key point is that the kit itself doesn’t create big power. Its value is in creating a known, fresh sealing and timing foundation around which you can build the rest of the EJ20.

For a high-output EJ20, the important engineering decisions then become piston-to-wall clearance, ring gap, bearing clearances, deck/head flatness, compression ratio, cylinder sealing, fastener strategy and ECU calibration. The TOMEI kit is one part of that much larger system.

Bottom line: 1964493151 is the 93.5-mm × 1.5-mm Full O/H Kit, and it makes particular sense when you’re doing a genuine EJ20 teardown/rebuild rather than merely replacing a head gasket. 

TOMEI ENG O H KIT FULL BL5 BP5 93.5-1.5 FOR SUBARU IMPREZA WRX STI EJ20 1964493151