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Before final installation of the cylinder heads, several things need to be checked to assure proper engine operation: 1. Piston to valve clearance – Minimum intake valve clearance should be .080″. Minimum exhaust valve clearance should be .100″. The point of minimum intake valve to piston clearance will usually occur somewhere between 5 and 15º ATDC during valve overlap. The point of minimum exhaust valve to piston clearance will usually occur 15º to 5º BTDC during valve overlap. Re-machining of the piston top eyebrows may be required with some pistons. 2. Proper lifter adjustment and rocker geometry – Check Lifter pre-load. Check clearance of push rod to guideplate. Rocker geometry should be checked making sure that the contact point of the roller remains properly on the valve tip and does not roll off the edge. Visual inspection of the rockers, valve springs, retainers, and pushrods should be made to ensure that none of these components come into improper contact with each other. If problems with valve train geometry occur, simple changes such as pushrod length may have to be made. OTHER ASSEMBLY TIPS When installing the sparkplugs and exhaust headers, be sure to use a high temperature anti-seize compound on the threads to reduce the possibility of thread damage in the future. Do not exceed a torque of 25 ft./lbs. on the intake manifold bolts and lubricate the bolt threads prior to assembly. If pushrod to cylinder head contact is a problem, loosen rocker studs and re-position guideplate as needed for clearance. INSTALLATION: Installation is the same as for original equipment cylinder heads. Consult service manual for specific procedures, if necessary. For 350 and smaller engines, use Fel-Pro head gasket #1003. #1003 has a flattened steel O-ring around each bore and will provide an excellent, long lasting seal. However, it will compress the aluminum and you must use #1003 for subsequent gasket changes to get a good seal. For 400 c.i.d. small blocks, use Fel-Pro #1014. YOU MUST DRILL “STEAM HOLES” IN CYLINDER HEADS FOR 400 ENGINES (see Figure 2). Be sure that the surface of the block and the surface of the head are thoroughly cleaned to remove any oily film before installation. Use alcohol or lacquer thinner on a lint-free rag to clean. Apply Loctite PST or suitable thread sealer to head bolt threads. Torque to 65 ft./lbs. in three steps (30-50-65) following the factory tightening sequence (see Figure 1). A re-torque is recommended after initial start-up and cool-down (allow 2-3 hours for adequate cooling)
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Chevrolet Aluminum Cylinder Heads INSTALLATION INSTRUCTIONS
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