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Lift and intake closing?

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Old Jul 3, 2017 | 07:03 AM
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We use the S&S .583 cams in touring builds from 95" to 107",they work very well in heavy bikes
 
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Old Jul 3, 2017 | 07:12 AM
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To the OP, what is your standard cruising RPM ? That will determine if you want a S&S 509/551/583 type cam or a high RPM (4500) cam. Also, what is your compression ratio ? IMHO, you should be looking for a torque curve that peaks at your cruising RPM, but I could be wrong.
 
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Old Jul 3, 2017 | 10:54 AM
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My cruising RPM is 2800, and my CR is 10.2:1
 
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Old Jul 3, 2017 | 03:22 PM
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Originally Posted by HDSAE60
My cruising RPM is 2800, and my CR is 10.2:1
s&s 570 is your cam then

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Old Jul 3, 2017 | 04:01 PM
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Originally Posted by HDSAE60
It seems like cams with early intake closing all have low or stock lift, why can't I find a cam with a intake closing at 27 ABDC and .585 lift?


My guess would be something to do with early closing is for bottom/mid range. This goes along with valve overlap, duration and cam noise (aggressive lift)
 
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Old Jul 9, 2017 | 02:37 AM
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Originally Posted by HDSAE60
My cruising RPM is 2800, and my CR is 10.2:1
I think my CR is more like 9.5:1. I have the cams out right now and will run a compression test without the cams in it and see what it really is.
 
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Old Jul 9, 2017 | 03:21 AM
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Originally Posted by HDSAE60
It seems like cams with early intake closing all have low or stock lift, why can't I find a cam with a intake closing at 27 ABDC and .585 lift?
Because a higher lift cam needs longer to close the valve than a lower lift cam if you don't want it to be too noisy or slam the valve shut too hard. Basically, there's further for the valve to travel so it needs more time. Plus, at that quadrant, right down near BDC, a few degrees of crank travel does not translate to a lot of piston movement so it does not make a huge difference to working compression etc to let it stay partially open a few degrees more. Live everthing in engine building, it's all compromises.
 
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Old Jul 9, 2017 | 03:30 AM
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You would probably like a CR 570-2 at 9.5. A 31 tooth pulley and a real dyno tune would do it
 
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Old Jul 9, 2017 | 02:32 PM
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Originally Posted by HDSAE60
I think my CR is more like 9.5:1. I have the cams out right now and will run a compression test without the cams in it and see what it really is.
Not a good way to measure compression.. Need the valves working.. Can do a leak test tho..
 
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Old Jul 9, 2017 | 04:34 PM
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Originally Posted by Max Headflow
Not a good way to measure compression.. Need the valves working.. Can do a leak test tho..
I want to measure Static Compression, then with the cams in look at dynamic compression.
 
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