How to choose a camshaft
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===Lift=== | ===Lift=== | ||
| − | Lift is a number that is best matched to your cylinder heads. Head flow for common domestic head castings can be found | + | Lift is a number that is best matched to your cylinder heads. Head flow for common domestic head castings can be found [http://users.erols.com/srweiss/tablehdc.htm '''here''']. Heads are flow tested at different lift levels, and at different amounts of "depression" (usually measured in in/Hg). When comparing heads, be sure the depression is similar, or be prepared to convert the results from one depression to another depression, using a calculator. Another difference that can be found when comparing head flow, is the size of the cylinder the head is sitting over, and yet another thing is whether an intake manifold is in place (rarely done), or if an exhaust tube is in place (more common), or is clay is used to radius the openings (fairly common). |
| − | More lift is generally better provided two things are addressed: the valves, retainers, and springs are capable of the lift you plan without binding, and the heads flow more as the valve is lifted higher. If a head port starts decreasing flow above 0.500" lift, there is no reason to try to use a 0.700" lift cam, but in most cases more lift is better up to the point where the heads start losing flow. Since the aftermarket has different rocker ratios available for most engines, the lobe lift of the cam can result in more lift than the stock ratio rockers would give. | + | More lift is generally better provided two things are addressed: the valves, retainers, and springs are capable of the lift you plan without binding, and the heads flow more as the valve is lifted higher. If a head port starts decreasing flow above 0.500" lift, there is no reason to try to use a 0.700" lift cam, but in most cases more lift is better up to the point where the heads start losing flow. Since the aftermarket has different rocker ratios available for most engines, the lobe lift of the cam can result in more lift than the stock ratio rockers would give. |
===Ramp speed/lobe intensity=== | ===Ramp speed/lobe intensity=== | ||
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