THO – A Small Company with Big Ambitions
Horiuchi Shoten Co., the owner of the THO brand, was established in Japan in 1957. It is a producer of seals and gaskets for machinery, household appliances, and internal combustion engines. In its home country, the brand is renowned for manufacturing high-quality gaskets (for cylinder heads, oil pans, and valve covers), crankshaft and camshaft seals, and valve stem seals. THO spare parts are popular not only among everyday drivers but also within the tuning community. In Japan, the company also offers customised gasket kits designed for engines equipped with turbochargers, including decompression head gaskets. These specialised kits are also sold through tuning shops in the USA.
THO operates as a relatively small-scale manufacturer based in Misato, on the outskirts of Tokyo. Despite employing fewer than 100 people and producing all products in a single facility, its components are available worldwide. The company’s low production capacity means it focuses almost exclusively on parts for Japanese cars and motorcycles.
This specialisation and dedication to quality create a combination that makes THO crankshaft system gaskets and seals a top choice among enthusiasts of Japanese automotive engineering.
THO Gaskets and Seals – Precision Technology
THO seals used in crankshafts, timing systems, and cylinder heads are crafted from advanced polymers such as fluorocarbon rubber (FKM), which is resistant to high temperatures and pressure, with low ageing rates and excellent elasticity, as well as nitrile butadiene rubber (NBR) known for its outstanding oil resistance. These materials are also used by larger sealing manufacturers, ensuring that THO products meet the performance standards of top-tier brands.
Thanks to small-batch production, each gasket is meticulously crafted under the supervision of an experienced technician, using modern automatic and semi-automatic machinery. Every part is securely packaged to protect against moisture and mechanical damage.
By choosing THO, you can be confident in the quality and perfect fit of components for your engine.
THO – A Sealed Engine is a Functional Engine
Maintaining the integrity of an engine's sealing systems is crucial for its proper operation. This prevents oil loss, excessive air intake, maintains cylinder pressure, and stops coolant leaks.
When you choose a THO cylinder head gasket, you can trust that the seal between the head and the engine block will be flawless, ensuring separation of oil channels from water channels during engine operation. Valve seals prevent oil from entering the cylinder, a common issue in older Japanese engines. This minimises oil consumption and reduces harmful deposits in the combustion chamber that can damage cylinder walls.
O-rings and crankshaft and camshaft seals retain oil in the bearings, preventing it from being expelled by pressure and centrifugal force in the event of a leak.
Valve cover and oil pan gaskets prevent leaks, helping to keep your engine clean, maintain oil levels between changes, and stop environmental contamination by engine oil.
THO gaskets are available for a wide range of Japanese vehicles, including rare, older models and those originally sold primarily in the Japanese domestic market. The brand's catalogue even includes seals for Honda and Toyota models from the 1970s and 1980s, which are often unavailable in authorised service centres, as well as older generations of popular sports models like the Honda Civic and CRX performance variants. This is a significant advantage for the growing number of fans of classic Japanese cars. THO products undoubtedly simplify the restoration and repair of these vehicles.