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Chevrolet Equinox Service Manual: Valve and Seat Grinding Seats

Chevrolet Equinox Service Manual / Body / Seating / Valve and Seat Grinding Seats

Valve Measurement and Reconditioning OverviewProper valve service is critical to engine performance.Therefore, all detailed measurement procedures must be followed toidentify components that are out of specification.If the measurement procedures reveal that the valve or valveseat must be reconditioned, it is critical to perform themeasurement procedures after reconditioning.Valve Seat Width Measurement Procedure

Valve and Seat Grinding Seats

Measure the valve seat width in the cylinder head using aproper scale.

Valve and Seat Grinding Seats

Measure the seat width-(b) on the valveface-(1) using a proper scale.

Note:The seat contact area must be at least0.5-mm-(0.020-in) from the outerdiameter, margin-(a), of the valve. If the contact areais too close to the margins, the seat must be reconditioned to movethe contact area away from the margin.

Compare your measurements with the specifications listed inEngine Mechanical Specifications.If the seat widths are acceptable, check the valve seatroundness using the Valve Seat Roundness MeasurementProcedure.If the seat width is not acceptable, you must grind the valveseat using the Valve and Seat Reconditioning Procedure to bring thewidth back into specification. Proper valve seat width is criticalto providing the correct amount of valve heat dissipation.Valve Seat Roundness Measurement ProcedureMeasure the valve seat roundness using a dial indicatorattached to a tapered pilot installed in the guide. The pilotshould have a slight bind when installed in the guide.

Caution:The correct size pilot must be used. Do not use adjustablediameter pilots. Adjustable pilots may damage the valveguides.

Compare your measurements with the specifications listed inEngine Mechanical Specifications.If the valve seat exceeds the roundness specification, youmust grind the valve and valve seat using the Valve and SeatReconditioning Procedure.If new valves are being used, the valve seat roundness mustbe within 0.05-mm (0.002-in).Valve Head O.D. and Chamfer Measurement Procedure

Valve and Seat Grinding Seats

Measure the valve head O.D. and chamfer-(a) usingan appropriate scale. Refer toEngine Mechanical Specifications.If the valve head O.D. and chamfer is within specification,test the valve-(1) for seat concentricity using theValve-to-Seat Concentricity Measurement Procedure. Reinspect thevalve head O.D. and chamfer after completing the concentricitymeasurement if valve seat reconditioning is performed.Valve-to-Seat Concentricity Measurement Procedure

Note:

Checking the valve-to-seat concentricity determines whetherthe valve and seat are sealing properly.You must measure the valve face and the valve seat to ensureproper valve sealing.

Valve and Seat Grinding Seats

Coat the valve face-(3) lightly with bluedye-(1).Install the valve in the cylinder head.Turn the valve against the seat with enough pressure to wearoff the dye.Remove the valve from the cylinder head.Inspect the valve face.If the valve face is concentric, providing a proper seal,with the valve stem, a continuous mark-(2) will be madearound the entire face.

Note:The wear mark MUST be at least 0.5-mm(0.020-in) from the outer diameter, themargin-(a), of the valve. If the wear mark is too closeto the margin, the seat must be reconditioned to move the contactarea away from the margin.

Note:Do not grind or condition the intake valve. If the intakevalve is out of specification, replace the valve.

If the face is not concentric with the stem, the mark willNOT be continuous around the valve face. The valve should berefaced or replaced and the seat must be reconditioned using theValve and Seat Reconditioning Procedure.Valve and Seat Reconditioning Procedure

Valve and Seat Grinding Seats

Note:

If the valve seat width, roundness or concentricity is beyondspecifications, you must grind the seats in order to ensure properheat dissipation and prevent the build up of carbon on theseats.It is necessary to reface the valve if seat reconditioning isrequired unless a new valve is used.Grind the valve seating surface-(a) to the properangle specification-(2) listed inEngine Mechanical Specifications.Grind the valve relief surface to the proper anglespecification-(1) listed inEngine Mechanical Specifications, to correctly position thevalve seating surface-(a) to the valve.Grind the valve undercut surface to the proper anglespecification-(3) listed inEngine Mechanical Specifications, to narrow the valveseating surface width-(a) to the specifications listedinEngine Mechanical Specifications.

Note:Do not grind or condition the intake valve. If the intakevalve seat has been reconditioned, replace the corresponding intakevalve.

Replace the intake valve if it is out of specification. RefertoEngine Mechanical Specifications.If the original exhaust valve is being used, grind the valveto the specifications listed inEngine Mechanical Specifications. Measure the valve headO.D. and chamfer again after grinding using the Valve Head O.D. andChamfer Measurement Procedure. Replace the exhaust valve if it isout of specification. New valves do not require grinding.When grinding the valves and seats, grind off as littlematerial as possible. Cutting valve seat results in lowering thevalve spring pressure.Install the valve in the cylinder head.If you are using refaced exhaust valves, lap the valves intothe seats with a fine grinding compound. The refacing and reseatingoperations should leave the refinished surfaces smooth and true sothat minimal lapping is required. Excessive lapping will groove thevalve face and prevent a good seat when hot.Be sure to clean any remaining lapping compound from thevalve and seat with solvent and compressed air prior to finalassembly.After obtaining the proper valve seat width in the cylinderhead, you must re-measure the valve stem height using the ValveStem Height Measurement Procedure.If the valve stem height is acceptable, test the seats forconcentricity using the Valve-to-Seat Concentricity MeasurementProcedure.Valve Stem Height Measurement Procedure

Valve and Seat Grinding Seats

Note:To determine the valve stem height measurement, measure fromthe valve spring seat to the valve spring retainer.

Install the valve-(1) into the valve guide in thecylinder head-(2).Ensure the valve is seated to the cylinder head valveseat.Install the valve stem oil seal.Install the valve spring retainer and valve stemlocks.Measure the distance-(a) between the valve seallip to the bottom of the valve spring retainer. Refer toEngine Mechanical Specifications.If the maximum height specification is exceeded, a new valveshould be installed and the valve stem height re-measured.

Caution:DO NOT grind the valve stem tip. The tip of the valve ishardened and grinding the tip will eliminate the hardened surfacecausing premature wear and possible engine damage.

Caution:DO NOT use shims in order to adjust valve stem height. Theuse of shims will cause the valve spring to bottom out before thecamshaft lobe is at peak lift and engine damage couldresult.

If the valve stem height still exceeds the maximum heightspecification, the cylinder head must be replaced.
Valve and Seat Grinding Seats
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