Cal Grinding, Inc. Typical Tolerances For Engine Valve Remanufacturing |
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You can view/download copies of the drawing in Adobe Acrobat® (PDF) or picture (JPG) formats.Overall Length (A): The total length of the valve, as received.Same Length (T): Our remanufacturing process allows us to provide you with valve sets that are the same length (as measured from the face to the tip) to help you adjust for heads that may have been decked or milled. This eliminates problems associated with different valve lengths, such as improper rocker arm geometry or improper lifter preload.Pre Grind Length Before Chrome (R): Standard sized valves have their stems pre-ground undersize in preparation for the hard chrome plating. This ensures that you have at least 0.0015 in. of hard chrome per per side after electroplating and finish grinding. Proper length must be maintained for plating purposes.Pre Grind Length After Chrome (C): After chrome plating, embrittlement baking and adhesion testing, each plated valve is pre-ground. This step, although more time consuming, brings the valve close to its finished size, allowing us to control our finish grinding operation more accurately. Proper length must be maintained for finish grind purposes.Minimum Chrome Length (Q): The minimum length of hard chromium applied to the valve stem as measured from the valve tip.Finish Grind Length (B): The minimum length, as measured from the valve tip, for which we maintain our finish grinding specifications of surface finish, stem diameter, and lobing.Minimum Clean Up (P): The absolute minimum finish ground stem length.Minimum Margin (L): The minimum length of the head at its major O.D. (lip thickness) may be affected by face grinding and is therefore monitored as needed.Head Diameter (J): The major O.D. of the valve remains unchanged.Face Angle (K): The face is finished to the exact angle you need to ensure proper seating with the seat.Original Stem Diameter (F): The outer diameter of the stem as received.Taper (E): When specified, the finished diameter of the valve may be larger at the tip end and smaller at the head end very accurately. Typically taper is only provided on certain exhaust valves to allow for thermal expansion at the head end.Finish Grind Diameter (H): The final stem diameter that is achieved throughout the finish grind length.Pre Grind Diameter After Chrome (I): The initial stem diameter that the valve is ground to following hard chrome plating. This diameter is maintained throughout the entire Pre Grind Length After Chrome.Plated Diameter (G): As the valve stems are hard chrome plated, their diameters are monitored to ensure that the proper thickness of chrome is applied.Tip To Chrome (D): The length of valve that is not plated such that the keeper grooves are not affected.Minimum Tip Hardness (U): We verify the tip hardness on 100% of all exhaust valves or any valve known to have a history with hardness problems. Any valve not meeting your minimum specification is rejected.Pre Grind Diameter Before Chrome (S): The initial stem diameter that the valve is ground to prior to hard chrome plating. This diameter is maintained throughout the entire Pre Grind Length Before Chrome.Stem Type (M): Refers to the keeper groove style. The groove area is cleaned and inspected and is otherwise unchanged from the as-received condition. Grooves are not plated or repaired in any way. Any part found to have worn grooves is rejected.
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