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post #1 of 4 (permalink) Old 03-19-05, 02:27 PM Thread Starter
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Cam Selection Confused

When selecting a solid cam the manufacturers quote advertised duration and lift. Some quote their figures at 0.020 lobe lift and others do not make any reference to their advertised numbers. Do advertised figures count or should one only look at 0.050 numbers? As an example the crane F238 advertised readings are far bigger than the F246, (overlap 89 compared to 71deg)! Also valve lift would always be less the lash clearance!

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post #2 of 4 (permalink) Old 03-19-05, 04:33 PM
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Re: Cam Selection Confused

Look @ the 0.050 numbers. It's quite common to use them for comparison. Other figures such as lift and lobe separation are to be considered also. The cam needs to suit the heads. Otherwise the time/figures won't happen.

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post #3 of 4 (permalink) Old 03-19-05, 06:07 PM
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Re: Cam Selection Confused

Quote:
Originally Posted by northiam
When selecting a solid cam the manufacturers quote advertised duration and lift. Some quote their figures at 0.020 lobe lift and others do not make any reference to their advertised numbers. Do advertised figures count or should one only look at 0.050 numbers? As an example the crane F238 advertised readings are far bigger than the F246, (overlap 89 compared to 71deg)! Also valve lift would always be less the lash clearance!
Like benx said, the 50 thou duration is important, as that is when the airflow realy starts, or is comparable between camshafts. Also, dont worry about subtracting the lash to look at lift on solid cams. Look at the lift that is advertized by the cam manufacturer. Most people have an idea of what sort of lifts they are after for their application.

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post #4 of 4 (permalink) Old 03-20-05, 02:12 AM
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Re: Cam Selection Confused

Some years back cam grinders recognised that their advertised duration figures were confusing to buyers and collectively began using .050" lobe lift as a common measurement. "Advertised duration" is exactly that and little notice need be taken of it.

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