Estimating timing chain wear
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==Adjusting the cam phasing== | ==Adjusting the cam phasing== | ||
| − | Cam phasing is the relationship of the camshaft position to the crankshaft position in reference to TDC. Many timing sets have multiple keyways | + | 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. Many timing sets have multiple crankshaft keyways that allow changes to the cam phasing like seen above on the chain and gear-type timing sets. There are other forms of adjustability like seen on the belt drive above where the cam gear is adjustable (there are chain-type timing sets that use this as well). |
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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. | ||
[[Category:Engine]] | [[Category:Engine]] | ||
[[Category:Adjust valves]] | [[Category:Adjust valves]] | ||
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