Our MAP valves feature black oxide nitrating (a superior hardening process) which penetrates into the ultra-EV8 stainless steel core material, forming a super-hard outer layer. This "Black Diamond" finish adds surface hardness as well as a smoother exterior coating which greatly reduces friction. This reduction in friction allows for tighter tolerances (fit) and provides long-lasting durability.
These valves are vastly superior to factory valves and other so-called "performance" finishes such as hard chrome.
Our induction welded, heat-treated tip prevents mushrooming and eliminates the need for lash caps.
Our oversized valves (OS) are flow tested for maximum performance.
Oversized valves can also be used to rejuvenate sunken valve seats while correcting valve geometry.
The OS valve features relocated keeper locations to accommodate hi-lift racing cams and springs. This saves additional machining expense.
NOTE: Always be sure to check piston clearance before installing oversize valves.
1964-73, 650cc T120 Bonneville and TR6 Trophy/Tiger models (from engine number DU 5825)
1973-82, 750cc T140 Bonneville and TR7 Tiger models.