Camshaft install tips and tricks
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*[http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=CC&Product_Code=159&Category_Code= Comp Cams Engine Break-In Oil Additive] | *[http://www.compperformancegroupstores.com/store/merchant.mvc?Screen=PROD&Store_Code=CC&Product_Code=159&Category_Code= Comp Cams Engine Break-In Oil Additive] | ||
*[http://www.hotrodders.com/forum/assembley-lube-good-anything-174183.html#post1239633 Hotrodders forum thread on cam and assembly lubricants] | *[http://www.hotrodders.com/forum/assembley-lube-good-anything-174183.html#post1239633 Hotrodders forum thread on cam and assembly lubricants] | ||
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| + | ==Adjusting the cam timing or "phasing"== | ||
| + | Cam phasing is the relationship of the camshaft position to the crankshaft position in reference to TDC. A change of 2 degrees at the cam gear equals 4 degrees at the crank. | ||
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| + | {{Note1}}When advancing/retarding the cam, be sure to check valve to piston clearance. Each degree of change effects valve clearance approximately 0.010". Example: If you advance the camshaft 4 degrees, you will '''lose''' about 0.040" clearance between the intake valve and piston, and you will ''gain'' about 0.040" clearance between the exhaust valve and piston. It will be the opposite if the camshaft is retarded. | ||
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| + | The cam timing, or phasing, can be changed at the time of installation by using a multi-keyway timing set, or an adjustable cam gear like [http://www.cloyes.com/HighPerformance/Products/HexAJustTrueRollerSets/tabid/383/language/en-US/Default.aspx Cloyes Hex-A-Just]. | ||
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| + | On timing sets that have no built-in adjustability, the cam phasing can still be adjusted in many cases. This is done by drilling the dowel pin hole of the cam gear oversize in order to use a bushing to advance or retard the cam gear. On engines where this isn't practical, an offset crank gear Woodruff key can often be used instead. | ||
| + | {| | ||
| + | |[[File:Cam bushings.jpg|thumb|center|280px|Cam gear bushing selection]] | ||
| + | |[[File:Offset crank keys.jpg|thumb|center|250px|Crank gear offset key selection]] | ||
| + | |} | ||
| + | In the majority of cases, installing the cam "straight up" (without any advance/retard added by the installer) is the correct way to install the cam and timing set. Many cam makers have already advanced (in most cases) the cam timing when the cam was made to suit the application. Unless the builder has access to an engine dynamometer or has advanced knowledge of the dynamics involved, advancing/retarding a cam is nothing but a shot in the dark as to whether it will result in any benefits at all. And there's the chance the engine output could be adversely affected by indiscriminately changing the phasing of the cam. The piston to valve clearance can be reduced enough to cause damage in some cases. | ||
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| + | ==Effects of changing cam timing== | ||
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| + | ===Advance timing=== | ||
| + | *Open Intake Valve Sooner | ||
| + | *Builds more low-end torque | ||
| + | *Decreases piston to intake valve clearance | ||
| + | *Increases piston to exhaust valve clearance | ||
| + | |||
| + | ===Retard timing=== | ||
| + | *Keeps intake valve open later | ||
| + | *Builds more upper RPM power | ||
| + | *Increases piston to intake valve clearance | ||
| + | *Decreases piston to exhaust valve clearance | ||
| + | |||
| + | ==Effects of changing lobe separation angle== | ||
| + | The lobe separation angle (LSA) is ground into the cam at the time of manufacture and cannot be changed by the installer. | ||
| + | |||
| + | ===Widen (larger) LSA=== | ||
| + | *Raises torque to higher RPM | ||
| + | *Reduces maximum torque | ||
| + | *Broadens power band | ||
| + | *Reduces maximum cylinder pressure | ||
| + | *Decrease chance of engine knock | ||
| + | *Decrease cranking compression | ||
| + | *Decrease effective compression | ||
| + | *Idle vacuum is increased | ||
| + | *Idle Quality improves | ||
| + | *Overlap decreases | ||
| + | *Natural EGR effect is reduced | ||
| + | *Increases piston-to-valve clearance | ||
| + | |||
| + | ===Tighten (smaller) LSA=== | ||
| + | *Moves torque to lower RPM | ||
| + | *Increases maximum torque | ||
| + | *Narrow power band | ||
| + | *Builds higher cylinder pressure | ||
| + | *Increase chance of engine knock | ||
| + | *Increase cranking compression | ||
| + | *Increase effective compression | ||
| + | *Idle vacuum is reduced | ||
| + | *Idle quality suffers | ||
| + | *Overlap increases | ||
| + | *Natural EGR effect increases | ||
| + | *Decreases piston-to-valve clearance | ||
==Roller cams are '''not''' immune== | ==Roller cams are '''not''' immune== | ||
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