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Manley Valve Locks
7° vs
Super 7° vs 10° Valve Locks
The original stamped 7° valve lock served the industry well until drag racers
discovered the Vasco Jet valve spring in the early 1970's. The use of previously
undreamed-of spring pressures caused periodic failures as the little 7° lock was
vulnerable to extrusion through the retainer.
Drag race engine builders seized upon the evidence of locks pushed through
retainers as proof of the inadequacy of the 7° design. Hence was born the 10°
lock to combat lock extrusion. In realty, the problem with the 7° lock was not
the angle. The 7° lock was simply too skinny to provide enough resistance to
being pushed through the retainer.
Meanwhile, circle track engine builders responded to the same challenge with a
Super 7° lock that maintained the superior clamping properties of the original
7° piece, but overcame the extrusion problem with increased lock thickness.
Conventional Versus Bead Loc Valve Stem Grooves
The groove in a valve stem, seemingly unimportant, in reality is vital to the
success of a valve’s performance. Imperfectly formed grooves,
inferior or mismatched locks, and improper retainers can lead to catastrophic
failure.
The so called “conventional” or square groove design has enjoyed enormous
success. But the success of a “conventional” groove is not a given. First, the
surface finish of the groove must be outstanding to guarantee against failure
due to residual machining marks.
Next, the groove must have a precise .013" radius in the upper corner. Too small
a radius leaves the groove subject to the dangers of a sharp fillet. Too large a
radius leaves open the possibility of the groove being abraded in this area by
the upper inside edge of the tang of the lock. Also, an oversized radius leaves
a reduced horizontal shelf in the groove which is - or should be - the only
contact point with the tang of the lock. Contact by
the lock in the root of the groove is a disaster waiting to happen.
Perfectly formed “conventional” grooves with proper locks and retainers will
deliver good service. However, there are a lot of junk components on the market
that can conspire to destroy a correctly machined groove.
The essence of the Bead Loc® groove is its simplicity and forgiveness. The
groove itself is a straight - forward .110" full radius. The contact points with
a Bead Loc® radius lock are approximately 2:00 and 10:00 o’clock, not at the
root of the groove. This system affords minimal vertical movement, especially
when valve float is present, which means reduced erosion of the valve for
enhanced service life. |
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Stamped locks are recommended ONLY for mild performance engines.