What's the formula for overlap? My search button isn't working right now? Thanks.

 

Int. dur + Exh. dur / 4 - LSA *2

 

{(Int dur+Exh dur)/2- (2xlsa)}=Degrees of overlap at .050.

 

Either formula above nets the same end result.

 

Let us say 224/224 114lsa @ .050
so first formula (224+224/4)- (2x114)= -116
Second formula (224+224/2)- (2x114)= -4

How are these results the same??

 

The first formula should read (224+224)/4-(114)*2=-4

 

So, do I want overlap to be closer to zero or further away? With my current cam I'm getting -14*, which performs great and sounds very badass. Then one of the ones I'm looking at for my LS1 (218/222-113) is -6* and the other one I'm looking at (220/224-113) is -4*. The -6* would give more lope of these two, right?

 

http://users3.ev1.net/~black_ops/cam...Calculator.xls

 

The less overlap the less lope.
(-) less lope
(+) more lope

 

Not to sound stupid, so the -6* will lope more than the -14*, right? If so, that makes sense why I kept getting the numbers I did when changing the LSA.

 

Quick and Dirty Cam Calculator Spreadsheet
0.050
Intake Duration - ID 220
Exhaust Duration - ED 224
Lobe Center Angle - LCA (also known as LSA) 113
Intake Centerline - ICL 113


Intake Valve opens - IVO -3
Intake Valve closes - IVC 43
Exhaust Valve Opens - EVO 45
Exhaust Valve Closes - EVC -1
Exhaust Centerline - ECL 113
Overlap -4

Quick and Dirty Cam Calculator Spreadsheet
0.050
Intake Duration - ID 218
Exhaust Duration - ED 222
Lobe Center Angle - LCA (also known as LSA) 113
Intake Centerline - ICL 113


Intake Valve opens - IVO -4
Intake Valve closes - IVC 42
Exhaust Valve Opens - EVO 44
Exhaust Valve Closes - EVC -2
Exhaust Centerline - ECL 113
Overlap -6


Neither should have much lope... The second one will have less though if any...

 

Cool, thanks!

 

What he said. I guess there where 2 diffrent ways of looking at the other guys formula.

 

Some people think that LSA determines overlap.

Overlap is amount of time the exhaust lobe and intake lobe overlap each other. LSA is only a small component of this. Duration counts much more.

For example
210/216 106LSA cam = 1 degree of overlap at .050"
220/226 110LSA cam = 3 degrees of overlap at .050"
230/236 114LSA cam = 5 degrees of overlap at .050"

So even though my LSA got 4 degrees wider in each successive cam, the overlap grew as well. LSA and overlap do not necessarily go hand in hand.