Thread: basic cam questions,`

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76GMC1500, you had me nodding my head until you got to here...

"If you have a 292 duration cam with 110 degrees LSA, both valves will be open for 182 degrees of crankshaft rotation."

Duration and overlap are measured in crankshaft degrees. Lobe Separation Angle is measured in camshaft degrees. You're subtracting apples from oranges.

Both valves can't possibly be open for 182 degrees of crank rotation, not even at zero tappet lift. The motor would never fire and run.

Here's a typical 292 degree cam ground on 107 degree centers and showing 78 degrees of overlap @ 0.004" tappet lift and 18 degrees overlap @ 0.050" tappet lift.
http://www.cranecams.com/?show=brows...tType=camshaft

Here's a 320 degree duration cam ground on 108 degree centers and showing 104 degrees of overlap @ 0.0186" tappet lift and 64 degrees of overlap @ 0.050" tappet lift.
http://www.cranecams.com/?show=brows...tType=camshaft
This is the wildest solid lifter grind that Crane makes for the small block Chevy.

"Wider LSA's, greater than 110 degrees, mean more torque but at a cost of high rpm efficiency."

Sorry to disagree, but just the opposite is true. Narrower LSA's will give more low end torque, but peak sooner and lay down on you on the top.

" Tight LSA's can also be used to bleed off cylinder pressures in high compression engines that have problems with detonation at low rpms."

Sorry again, but it's actually the intake closing point that must be manipulated to alter cylinder pressure.