Thread: Cam duration

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Anyone care to take a stab at explaining cam lift and duration and the corrsponding numbers? I am a novice first time motor builder and have limited knowledge on the cam. I know what it does and have the basic principles down. I have replaced on before, but do not understand the calculations and how to correlate them to the differant types of performance. Anyone care to elaborate. thanks for helping someone learn!

Send for some of the Cam catalogs,Crane And Isky and others have a lot of good info in them,good thing to have for referance too!

Read this and you will be well on your way to understanding the camshaft and how it affects the engines power .
http://www.popularhotrodding.com/tec...ics/index.html

Originally Posted by 65Fairlane

Anyone care to take a stab at explaining cam lift and duration and the corrsponding numbers? I am a novice first time motor builder and have limited knowledge on the cam. I know what it does and have the basic principles down. I have replaced on before, but do not understand the calculations and how to correlate them to the differant types of performance. Anyone care to elaborate. thanks for helping someone learn!

To save a lot of studying and confusion, pick a cam company, fill out the spec sheet accurately and completely and go with the experts recomendations. Many seem to have the misconception that the cam is the most important thing in any build.....Actually it's a combination of many things with the cam being important but not the only thing that makes the car perform the way you want it too. For the ultimate cam, pay for the blank and the grinding, let the cam experts, and not the dummys on the phone bank at Jeg's, design a build the cam for your engine. Nothing wrong with learning more about cams, but unless you are a cam grinder yourself, not really a lot of reason to obtain a Doctorate in Camshaftology!!!!!

there's lot of good info at compcams tech page

i was going to add something but i guess i know nothing

i have my hand full working on my 2 helping of cherry apple sauce it good

i will give you a cookie pat if you say it....

the more i think i know about this the less i know and there is so many ways to get there from here. on the way lobe is formed. now they tell me with out the use of the old masters every thing is ground off computer. i wanted to go to one of them cam tech sems but never have the time . so if i can get the lsa were i want it and the dur @050. and lift . i gusse that will work but when i ask for a lobe pro file i want they tell me they not have a master like that ?????????

well that seams to be the way it is now days .this is what we have and if you do not like it tough and we do not want to talk to you about any of are cams . the only one that seam s to know any thing is erson cams and some others but the list is getting small

i just wanted to shine some light on *Lobe Separation Angle* (LSA)

You have the intake opening @ .050" and the intake close @ .050". Together these items make duration @ .050" and the intake center (IC).

You have the exhaust opening @ .050" and the exhaust close @ .050". Together these items make duration @ .050" and the exhaust center (EC).
Anyone how grinds camshafts goes about it from this avenue. They may look at different aspects of the engine in the designing phase by looking at velocity, pressures, cylinder pressure, etc, but in the simplest of terms, this is how it starts.

Basic math here.
The (IntakeCenter) + the (ExhCenter)/(2) = LSA
the average of the centers is the LSA. When you speak of camshafts in terms of LSA, When a person says LSA, what is he really saying?
Example.
I design a camshaft and I feel as though the events at .050" need to be:
IO = 15
IC = 55
EO = 66
EC = 14
Now put these together. The in @ .050" = 250* and the ex @ .050" = 260*. These events make the IC = 110 and the EC = 116. Thus.......
110 + 116 = 226.......226/2 = 113 LSA
In the above example, those EXACT opening & closing events yield the specs above. Period. Now when a guy comes along and says that a 113 LSA is a NOS cam, a motor cam should have tighter LSA (or more common going from motor to NOS) that ALL you need to do is change the LSA, you cannot just magically change the LSA. Its impossible.

Backwards. 116 + 110 = 226/2 = 113 EVERYTIME. But if I come at it and say I want a 113 LSA, how many different combinations of numbers can you have and get to 113? infinate amount... remember that all events of a cam happen in 180* cycles. with the ivo,ivc,evo,evc numbers you can tell the cam spec's other then lift. the other thing to consider is lifter acceleration rate. thats how fast the valve is opening.

Originally Posted by pat mccarthy

the more i think i know about this the less i know and there is so many ways to get there from here. on the way lobe is formed. now they tell me with out the use of the old masters every thing is ground off computer. i wanted to go to one of them cam tech sems but never have the time . so if i can get the lsa were i want it and the dur @050. and lift . i gusse that will work but when i ask for a lobe pro file i want they tell me they not have a master like that ?????????

so if the computer does it.... that means the old man with the bench grinder retired eh? i guess its the end of odd running cams