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Subaru valve seat machining services

Valve Seat Machining Services

The valve seat area is one of the most critical when it comes to airflow. This is especially true at lower valve lifts since your valves spend most of their time there, not at maximum lift. Average flow increases as high as 10% are obtainable with a valve seat cut alone, when the appropriate seat profiles are employed. These numbers are even more impressive knowing that they refer to modern four stroke motorcycle engines that see over 14,000 rpm regularly, with ports that are comparable to modern Formula 1 technology. Also be aware that all flow bench data numbers are taken before the valve seat cut operation is performed.

Super Street Valve Seat Machining

subaru engine cams
Machining is performed using a Sunnen Valve seat cutter: the same milling machine accuracy and repeatability of the famous Serdi. Multi angle cutter capabilities allow for dramatic increases in the cylinder port flow. Precise concentric cutter/machining operation makes for near perfect valve sealing without the need for grinding or lapping pastes that can reduce thermal transfer contact area. These pastes can be detrimental to satellite coated valves common in Japanese engines.

High Output Valve Seat Machining

subaru valve seat machining
Machining is performed by hand using a Peg grinder micrometer-fed, electric valve seat grinder. This machine oscillates about a vertical shaft and is fed into the valve seat with a micrometer feed on the top of this shaft. It allows for almost an infinite number of angles to be employed since the stones used are shaped and trued on the power head to a user defined shape or angle. Each angle is cut separately unlike the Sunnen or Serdi that cut all (usually three) angles at once. This requires significant operator skill so we use one of the best "superbike" head builders in the business. We also use this equipment to determine proper cutter angles for Sunnen valve seat cutter to reduce cost for the more common valve seat angle combinations.

Noticeable power increases across the entire power range correlate directly to improved sealing and flow.


Description Unit # Price* (US)
Valve Seat Machining   Per cylinder
* Super Street 2-Valve Head 00-SS-vsm-002 $ 35
** High Output 2-Valve Head 00-HO-vsm-002 $ 47
* Super Street 4-Valve Head 00-SS-vsm-004 $ 63
** High Output 4-Valve Head 00-HO-vsm-004 $ 75
* Super Street 5-Valve Head 00-SS-vsm-005 Call
** High Output 5-Valve Head 00-HO-vsm-005 $ 87
Contact us for more information
* 3 angles intake/exhaust   ** 5 angle intake/ 4 angle exhaust

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