# Sticky  Cam Basics



## GM4life (Mar 18, 2007)

*Lift:* Camshafts rotational motion is converted to linear motion by roller lifters following the lobes on the camshaft circumference. Lift designates the maximum distance the valve is lifted from its valve seat and is measured in thousands of an inch.

*Duration:* Duraation is the length of time, measured in degrees of crankshaft roation, that the valve is open. Duration is measured at .050" of valve lift. Another term is advertiszed duration witch refers to a point where lifter movement begains. There is no standard to meausureing adv duration. The standard is .050" what makes comparisons easier.
Increased duration means the valve opens sooner and closes later. Longer the valve is held open(intake valve) the more top-end power the engine will produce because there is more time to fill the cylinder at high rpm. A longer duration cam will make more peak horsepower than a short duration cam. Downsides is a longer duration cam will soften low and mid-range power. This is the later closing intake valve allows air and fuel in the cylinder to escape back into the intake manifold at low engine speeds. This is called reversion: the pressure in the vylinder is greater than the pressure in the intake.

*Lobe Separation Angle(LSA):* is the angular displacement between the centerlines of the intake lobe and its companion exhaust lobe. As lsa is increased overlap is decreased. This is given in cam degrees rather than crank degrees. A wide lsa in the 116 deg. range will provide asmooth idle, a broad torque band and reduce the engine sensitivity to a less than perfect combination. Tightening the lsa to 106 deg. would ultimately provide more power but expense of a narrow power band and a choppy idle. LSA's of 110 to 114 are usually best for engines that will see street dutyas well as the occasional foray at the track. A wider lsa improves idle quality by creating more intake manifold vacuum and allowing less reversion.

*Intake Centerline:* refers to the positon at which the cam is installed relative to the crankshaft. It tells us the angle in crankshaft deg at which max intake valve lift occure relative to Top Dead Center(TDC).
Example: an intake centerline of 106 deg. tells us that the intake valve reaches max lift at 106 deg. after TDC.
*-- Advancing or retarding the cam:* For example if you install a cam stright up at 108 deg. later you decide you want to advance the cam 2deg that will improve bottom end torque. Advancing means moving all opening and closing points two deg sooner. This changes the ICL from 108 to 106 deg. Retarding the cam two degrees from the 108 to 110 deg will open and close the valves later. This will improve top end power at expense of some low end torque. This is how VVT/cam phasing and simular setups manipulate engine output.

*Overlap:* Valve overlap is measure in crankshaft degrees. Occures at the pistion approaches and leaves TDC extending from the exhaust stroke of one cycle to the intake stroke of the next. LSA directly affects overlap. Increasing LSA decreases the amount of overlap. If the intake lobe centerline remains the same then spreading the lsa has the effect of leaving the intake lobe in place and advancing the exhaust lobe centerline. Decreasing LSA incrases overlap. This improves the volumetric efficiency through the engines midrange rpm by allowing better exhaust scavenging. Increasing overlap with a short duration cam is a way to increase torquein the midrange but sacrifices torque at lower ranges.


Work in progress!


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## GM4life (Mar 18, 2007)

*Forced Induction Cam basics*

Reserved...


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## BearGFR (Aug 25, 2008)

Another explanation of Overlap: Period of time, expressed in crankshaft degrees, when intake and exhaust valves are both open. Overlap therefore is determined by the combined effects of both duration and LSA. Shorter overlap cams will generally have good street manners and will produce ample manifold vacuum at idle for operating accessories such as power brake boosters, at the expense of a loss in volumetric efficiency (cylinder filling) at higher rpm. Longer overlap cams will tend to make better power at rpm due to improved volumetric efficiency resulting from the ability to take advantage of higher intake and exhaust flow rates, however low rpm torque and idle manifold vacuum will decrease as the long overlap period at lower flow rates tends to promote reversion, polluting the incoming intake charge with drawn-back exhaust gas. Overlap, more than any other characteristic, is what contributes to that "lumpy" idle we all associated with a 'hot' engine. 

(Good job, GM4Life :cheers)

Bear


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## Falco21 (May 11, 2010)

GrinyukGoat said:


> What would be the highest performance camshaft for an 05 GTO?


No definite answer to that. You should do a lot of searching and reading before asking questions of that nature


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## BearGFR (Aug 25, 2008)

GrinyukGoat said:


> What would be the highest performance camshaft for an 05 GTO?


"It depends"  What exactly do you mean by 'highest performance'? If you mean maximum "horsepower" at the expense of everything else (low rpm torque, street manners, fuel mileage, etc.) then it would be which ever cam moves the engine's point of peak volumetric efficiency (VE) to the highest rpm the rest of the rotating assembly can sustain without coming apart. An engine with such a cam though is going to be no fun to try to drive anywhere except on a race track running at or very near that rpm. Everywhere else it's going to be a dog, barely able to get out of its own way.

Bear


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## GM4life (Mar 18, 2007)

Ahh I need to finish this. Been busy, sorry folks.


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## The_Madcat (Sep 30, 2011)

GM4life said:


> Ahh I need to finish this. Been busy, sorry folks.


No worries, good start on it. I know I have enjoyed reading it and I am somewhat cam spec ignorant.


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## EvdoCommy (Aug 2, 2012)

*Looking for a good cam!*

Hello, i have a 2006 gto, it is magnacharged, has a full exhaust, and is meth injected (for detonation prevention not performance). I am looking to recam. i would like to broaden my power band. however i am having a hard time finding a good cam for a supercharged aplication. any advice on supercharger cams other than keeping overlap to a minimum?? thanks.


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## svede1212 (Nov 1, 2005)

Contact Ed Curtis at Flowtech Induction. He is a guru and custom cam grinder. He'll make sure you get a cam that will fit your use and needs. It will be better than internet advise from people with limited knowledge of cam operations.


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## brigos65 (Mar 28, 2013)

I just did a cam swap in my 06 GTO. New double roller timing gears, lifters, pushrods and, springs, cam .50 219 int. 227 ext lift 607 int. 614 ext @ 112 deg. RPM power band is 1500 to 6500 Comp part. #54-456-11. Well hears the shit storm I have and I could really use some advice!! I installed the cam straight up, reassembled the motor and started it up. I knew I was going to need the car tuned because the size of the lift. She’s running and…she has a very loud taping noise!!! Like not enough oil, a couple of lifters collapsed, or the stock rockers just can’t handle the cam????? I pulled the valve covers off to check if any push rods got bent… Nothing!! I got real good power even without the tune! My oil pressure is 40 to 45 psi. The car has never sounded like this until I installed the cam kit?? Any advice would be HUGELY APPRECIATED!!!!


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