doug791

allright i have a bunch of questions about cam selection and im going to post them up one by one so i can get answers and im sure ill be coming up with new questions with every answer i get.
btw anyone else feel free to pop up their questions up here too

okay #1 two different cams from comp cams
.050 1.5:1 lift
210/220 .480/.480
210/220 .500/.510


As i understand this this means the ramp angle is the same for both cams but the peak of the second one goes a little higher and therefor causes greater lift....how is this going to effect the way the engine performes?

Black6SpdTA

Cam 1 and Cam 2 have the same duration so they will obviously stay open the same lenth of time. For the split second that came 2 is at full "opening capacity," it is going to let a little more fuel and air in causing increased hp. Cam 2 *should* give you better overall RPM performance because at the same angle (angle of the cam lobe in relation to 360* total) it will be higher, opening the valve more. Im not sure what RPM range which would be better for. Maybe someone can enlighten? Man doug you got me all confused now!
-Rippin

doug791

i think basically the second one does the exuivalent of putting on larger rockers? It will merely increase lift at said duration meaning the valves would be open wider.

Next question
how do people say oh this cam is at 230 degrees at .050 duration. Most cams are different for the intake and exhaust so should you have numbers for both. Is it to be assumed the that the cam would be a single patern cam then?

Also im thinking theoretically that if your cam has higher lift the way that this could be a bad thing if the cam was lifting higher then the head has the capability to flow??? then youd just have a certain set of your duration that isnt accomplishing anything and is just hanging open.

doug791

also i dont understand what .050 is a relationship of
you talk about how many degrees at .050 and your lift goes all the way to .5++ so i dont see how .050 could be related to lift. So what is .050 a measure of and why is it of god like importance

EDIT : it has something to do with "tappet lift". What is that?

Black6SpdTA

I'm pretty sure tappet is flat tappet which is nowhere near as good as Hydraulic Roller

doug791

this is the quote from a chevyhiperformance tech article "The problem with advertising numbers was that not everyone used the same lobe-lift figure to determine duration. This led to significant confusion when it came time to compare numbers. Legend has it that Harvey Crane suggested that all the cam manufacturers use 0.050 inch of tappet lift as a common lobe-lift point that all cam manufacturers would use so that we could compare the cams. This is the number that most people use when referring to duration specs since it uses a common data point. For example, a Crane PowerMax 278 flat-tappet hydraulic has an advertised duration of 278 degrees on the intake and 290 degrees on the exhaust side. The duration at 0.050-inch tappet lift is 222 degrees on the intake lobe and 234 degrees on the exhaust."

here is the link to the tech article click me