Editing Camshaft install tips and tricks (section)
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===Checking clearances=== '''Note:''' More info on checking clearances at '''[[Valve train points to check]]'''. '''8. Failure to check for valve spring coil bind at max lift.''' If you cannot tell by eye, verify by inserting a .010" feeler gauge between the coils. A .010" between five coils would give a total of .050" safety margin before stacking the spring solid. If you cannot pass the feeler gauge between the coils, the spring is either coil bound or dangerously close to this condition, and you have probably over shimmed the spring (the fitted dimension is too short). '''9. Failure to check for retainer to valve guide/seal clearance.''' 1/16"-1/8" (0.0625"- 0.125") clearance at full valve lift is considered sufficient. The valve spring retainer to valve stem seal clearance at maximum lift is the limiting factor with stock L31 Vortec heads. Due to casting and manufacturing tolerances/differences, the retainer to seal clearance has to be checked on each head to determine what the maximum lift is for that head. Reports indicate that 0.450" valve lift is usually no problem, and as much as 0.480" lift has ''reportedly'' been used with nothing more than a different valve stem seal being used. GM says the limit is about 0.420" using all stock parts; this is supposed to allow for 0.030" retainer-to-seal clearance. More on the L31 Vortec heads '''[http://www.crankshaftcoalition.com/wiki/Vortec_L31_cylinder_head here]'''. '''10. Failure to check for binding at the rocker/stud interface with stamped steel rockers.''' Long slot rockers are made specifically to cure this problem. Quality roller rockers with a needle bearing trunnion are as good as it gets with a stud-mounted rocker. '''11. Failure to check for piston/valve clearance''' 0.080" on the intake and 0.100" on the exhaust is considered by many to be the minimum clearance acceptable. You will probably find the closest near-miss at the exhaust valve on overlap, when the piston is chasing the exhaust valve back onto its seat. '''12. Failure to clearance lifters in their bores.''' [[File:Grooved bores.jpg|thumb|550px|Grooved lifter bores]] Lifter clearance should be 0.0012" to 0.002", with 0.0015" (one and one half thousandths) considered close to ideal. Too loose can be as bad as too tight. One way to provide a flat tappet cam and lifters with additional lubrication is to groove the lifter bores. One tool for doing this operation is the Comp Cams p/n 5003 [http://www.summitracing.com/parts/CCA-5003/ lifter bore grooving tool] sold by Summit. Solid lifter flat tappet lifters are available with a small machined hole in the lifter foot that feeds pressurized oil to the interface between the cam and lifter. But having that hole is no guarantee (see photo below)... <br style="clear:both"/> {| |[[File:Bad cam and lifter edm.jpg|thumb|left|center|500px|Bad cam and EDM hole-equipped lifter]] |[[File:Grooving tool.jpg|thumb|500px|center|Lifter bore grooving tool set]] |}
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