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iTrader: (12)

LS7 cam - 505 HP - 28 mpg

211 - intake duration @ .050

230 - exhaust duration @ .050

120 - LSA (lobe separation angle) camshaft degrees

120 - intake/exhaust lobe centerline straight up in crank degrees

123 - ILC (intake lobe centerline) factory installed @ 3 degrees retard

.591 - intake valve lift

.591 - exhaust valve lift

As opposed to a dual camshaft setup, a single cam's LSA will be fixed at birth, it cannot be altered. The ILC/ELC can be advanced or retarded with one affecting the other. Advancing the ILC, retards the ELC.......retarding the ILC, advances the ELC, but the 120 LSA relationship will never change or will the overlap.

The factory installs the LS7 in the 3 degree retarded position:

123 - ILC - (Intake Lobe Center)
117 - ELC - (Exhaust Lobe Center)
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Quick overlap calc:

Add the in/ex duration
Divide by 4
Subtract the LSA
Multiply by 2

Example:

211 + 230 = 441

441 / by 4 = 110.25

110.25 - 120 = -9.75

-9.75 x 2 = -19.5

Overlap = -19.5 degrees of negative overlap
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Wide SLA = low, zero or negative overlap for good gas milage and emmision control

Wide SLA = relatively early exhaust valve opening for restrictive exhaust systems

Wide SLA = relatively late intake valve closing for controlling dynamic pressure with 11:1 CR

Massive intake port flow capability allows relatively low 211 intake duration combined with .591 lift

Increased exhaust duration of 230, combined with early exhaust opening and .591 lift helps combat restrictive street exhaust system.
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LS7 Cam profile @ ILC/ELC 120 straight up - 211/230 duration

IO......... -14.5 atdc

IC......... 45.5 abdc

EO......... 55 bbdc

EC......... -5 btdc

Overlap = -19.5 and 120 LSA
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LS7 Cam profile @ ILC/ELC 123/117 - 3 degree retard - 211/230 duration

IO......... -17.5 atdc

IC......... 48.5 abdc

EO......... 52 bbdc

EC......... -2 btdc

Overlap = -19.5 and 120 LSA
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Intake Timing calcs:

intake duration = 211

divide by 2 = 105.5

LSA = 120

subtract 120 from 105.5 = -14.5 IO

subtract -14.5 from 180 = 165.5

subtract 165.5 from 211 = 45.5 IC

Intake timing = IO -14.5 atdc --- IC 45.5 abdc
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Exhaust Timing calcs:

exhaust duration = 230

divide by 2 = 115

LSA = 120

subtract 120 from 115 = -5 EC

subtract -5 from 180 = 175

subtract 175 from 230 = 55 EC

Exhaust timing = EO 55 bbdc --- EC -5 btdc
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IO - -14.5 atdc

IC - 45.5 abdc

EO - 55 bbdc

EC - -5 btdc
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To advance the cam, subtract the amount of advance in degrees from the intake and add to the exhaust.


To retard the cam, add the amount of retard in degrees to the intake and subtract from the exhaust.


Straight up 120 - ILC/120 - ELC

IO - -14.5 atdc

IC - 45.5 abdc

EO - 55 bbdc

EC - -5 btdc


Example: 3 degrees advance becomes 117 - ILC/223 - ELC


IO - -11.5 atdc

IC - 42.5 abdc

EO - 58 bbdc

EC - -8 btdc
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Straight up 120 - ILC/120 - ELC

IO - -14.5 atdc

IC - 45.5 abdc

EO - 55 bbdc

EC - -5 btdc


Example: 3 degrees retard becomes 223 - ILC/117 - ELC


IO - -17.5 atdc

IC - 48.5 abdc

EO - 52 bbdc

EC - -2 btdc