The camshaft is the last component of my rebuild that I haven't decided upon yet. I'm trying to learn what I can about them so I can make an intelligent purchasing decision. Yes, I know this is a broad topic..
I don't understand the relationship between duration and lift.. what running aspects are changed as a result of increased duration? What aspects are changed as a result of increased lift? At what lift and/or duration should I worry about longevity issues?
There are so many numbers out there and the descriptions that go with each camshaft seem too vague. I can stare at the webcam page all day and still not know how different an 86 will be from an 86a or 86b.. or 494, etc etc etc. Can anyone help me or point me towards some resources that will help me translate these numbers a little better?
Thanks!
Are you an engineer ?? LOL
B
Here you go, this will either enlighten you or put you to sleep
http://www.manleyperformance.com/tech-report.html
I recommend you read the entire page, quiz tommorow
Do you know this guy?
HD Manley
Attached image(s)
That page was helpful, thank you. I understand, in general, how camshafts work.. I guess the question I should've asked was:
Two camshafts claim the same type of performance: improved midrange and strong bottom end for street engines with carbs. One cam has a longer duration and shorter lift compared to the other that has a higher lift and shorter duration. So how are they 'different'? (or which is 'better'?) Perhaps the answer is infinitely more complex than I'm imagining it is..
I am sure someone will chime in but I think high lift short duration cams are designed for high RPM motors. Long duration shorter lift cams make power lower in the RPM band. Or is it the other way around? At any rate, Type 4 motors (unless highly modified) are not known for their High RPM ability.
Part of the equasion is going to depend upon what you are going to use the car for. If you are looking for driveabilty don't put a radical cam in.
Depending on the valve train geometry, the higher lift cam might not work with stock springs before they would bind (compress and have each coil touch)
or piston to valve clearance might be too close and the higher lift valve could hit the piston top unless the piston is machined with a relief.
The high lift/short duration cam is ideal for a turbo motor since the incomming charge could end up going out the exhaust if the duration is too long (overlap)
the longer duration cam will have a weaker vacuum signal but it will be "gentler" on the valve train since it does not have to ramp up so fast to attain the higher lift
did that help or confuse you more
That made sense Mueller; that's what I was looking for. It reaffirmed my original thought that shorter lift/longer duration is gentler on the valve train. I can also see the reason for high lift/short duration on turbo motors.
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