GM Cutlass RWD 1970-1987 Repair Guide

Valve Seats



See Figures 1 and 2

All valve seat reconditioning procedures should be performed by a competent machine shop.

When reconditioning valves and valve seats, clean carbon from cylinder heads and valves, using care not to gouge or scratch machined surfaces. A soft wire brush is suitable for this purpose. Whenever valves are replaced, or new valves installed, the valve seats must be reconditioned.

Narrow the valve seats to the specified width. This operation is done by using a combination of different grinding stones to lower and raise the seat. See chart for valve seat width.

Intake valve seats are induction hardened and must be ground, not cut.

If valve guide bores are worn excessively, they can be reamed oversize. This will require replacement of the valves with oversize valves (stems). The guide bores should be reamed before grinding the valve seats.

Click image to see an enlarged view

Fig. Fig. 1: Cleaning valve guide bores - 263 diesel shown

Click image to see an enlarged view

Fig. Fig. 2: Reaming valve guide bores - 350 Oldsmobile built engine shown

  1. Lightly lap the valves into seats with the fine grinding compound. The refacing and reseating operations should leave the refinished surfaces smooth and true so that a minimum of lapping is required. Excessive lapping will groove the valve face preventing a good seat when hot.New valves should not be lapped under any condition as the nickel-plated surface on the exhausts will be removed.
  3. Test valves for concentricity with seats and for tight seating. The usual test is to coat the valve face lightly with Prussian blue, or equivalent, and turn the valve against seat. If the valve face is concentric with the valve stem a mark will be made all around the face, which if the face is not concentric with the stem, a mark will be made on only one side of the face. Next, coat the valve seat lightly with Prussian blue, or equivalent. Rotate the valve against the seat to determine if the valve seat is concentric with the valve guide, and if the valve is seating all the way around. Both of these tests are necessary to prove that a proper seat is being obtained.
  5. Remove any burrs from valve stem with a fine stone and polish with crocus cloth.
  7. Lubricate valve stems and guides with engine oil and reinstall valves.
  9. Install new intake valve seals. Do not install exhaust valve guide seals.
    1. Start valve seal carefully over valve stem. Push seal down until to touches top of guide.
    3. Use installation tool J-2509 or equivalent to push seal over valve guide until upper inside surface of seal touches top of guide.


Compress Springs Only Enough To Install Keepers. Excess Compression Can Cause Spring Retainer To Damage Valve Seal

  1. Install intake valve springs on the 350 cu. in. with closely-wound coil toward the cylinder head. Exhaust valve springs on the 350 engine and all valve springs for V-6 engine, may be installed with either end up.
  3. Reinstall valve spring, cap and cap retainer, using same equipment used for removal.

  1. Install cylinder head.