Camshaft question...do you know?

Question

...how the lobe separation angle affects the performance of a cam?

Answer 1

#1. Lobe centers or separation angles are defined as the angle of degrees @ top dead center of the intake lobe and the distance in degrees of top dead center of the exhaust lobe. Smaller overlap creates higher intake manifold vacuum and better throttle response and more torque. 110 degrees of lobe separation is best for street use. There are a bunch of variables to squeeze more power out of the same 109 - 112 degree lobe center camshaft. Some companies grind asymmetrical intake opening and exhaust profiles. This is where roller hydraulic lifters come in to play. Companies such as Comp Cams, Crane, Erson, Crower grind lobe shapes causing the intake and exhaust flank ground with a more aggressive oval ramp shape to get to tdc of the cam lobe faster. #2. A completly seperate issue is camshafts duration of the lobes @ .050 of cam lift. Slightly longer duration cams can gain power. Exhaust duration increase of 10 - 20 degrees increases exhaust velosity and decreases pressure of the gasses do to small poorly designed ports. A well desinged set of headers, big exhaust pipes and the largest inner core mufflers really can help. Duration on a street Chevrolet should'nt exceed 215 degrees on the intake side and 224 in the exhaust. #3.Total valve lift is the third consideration. A 350 can soak-up some added lift without bothering drivability. The GM. # 24502476 has .435 intake and .460 exhaust lift. makes power at the bottom and would make a good automatic trans. cam. For 21 other small block GM cam listings go to the GM 2006 Performance Parts Catalog part # 19157556. The 2007 catalog will be out in early March from any GM parts counter.

Answer 2

I agree with everyone except "dodge man". Lobe separation angle doesn't affect lift or duration. The angle is mearly the separation between the intake and the exhaust valves. The closer the angle, the more "overlap" the cam will have which means both valves are open at the same time. The exhaust is closing while the intake is opening. Close lobe separation is great for high winding race engines but, kinda sucks for street engines. More lobe separation is better for economy and bottom end torque. It's really all in what you are building the engine for. Different strokes for different folks. It's been said that most people over cam their engines and would be much more happy with a smaller cam.

Answer 3

Tighter LSA tends to produce more peak power, over a narrower RPM range. Wider LSA tends to produce slightly less peak power, but the overall powerband is wider. Also look at intake closing event, to compare dynamic compression ratio between cams. Later intake closing bleeds off cylinder pressure, and makes the car more rumpy. You lose low end, but gain midrange. Camshafts are all about tradeoffs. Correct cam is all about the application.

There is no such thing as too big a cam, just not enough motor. -old friend of mine.

Answer 4

Close separation is used for high performance applications, wide separation is for low emission applications. Dont forget, the cam profile is only one factor in how an engine behaves. There are some good books on how and why engines are designed as they are - we can all learn from them.

Answer 5

it's called overlap , the greater the amount of overlap the worse the idle will be , however at high engine speeds you will get better cylinder "scavenging" , the 1/4 mile crowd uses cams like this , a really rough idle but sheer music at 6500 rpm.

Answer 6

yes i do,it affects the lift of it as well as the duration and the timing of when the valves open on it.for instance an RV cam opens and closes less than a stock cam does allowing it to produce more horse power and torque at a lower rpm range,good luck, i hope this answers your question,

Answer 7

i agree with the other answers , of course, but i would like to add
having been in the auto parts business , people like melling,
who is the predominate cam manufacturer will have a customer
service line that can be provided through your local parts store
or if you check with them , perhaps directly. your parts man, whether its melling , trw, or any other line will have performance
specs in his catalog and will usually have extra catalogs available. customer service on the phone can answer any beyond the norm questions you may have. and don't be afraid to ask. this is a service they are expected to perform and should be
happy to. extra catalogs are usually available , with specs, and if not, google the company you like and they will mail you one.
good luck to you.