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heretic
09-16-2007, 06:04 PM
Does anyone know the how much valve clearance a stock 1990 automatic sc has?

With a change in cam and 1.73 ratio roller rockers is there a formula to calculate the new clearances other than checking by hand?

stock cam intake: .445" 192 degrees @ .050"
exhaust .457" 198 degrees @ .050"
lobe seperation 108 degrees

new cam options intake: .480" 204 degrees @ .050"
exhaust .480" 216 degrees @ .050"
lobe seperation 114 degrees

intake: .500" 210 degrees @ .050"
exhaust .500" 226 degrees @ .050"
lobe seperation 114 degrees

CMac89
09-16-2007, 07:50 PM
These motors have hydraulic lifters, which do NOT have lash. These lifters use PRELOAD.

Every cam that you can use should be preloaded .050". I means from zero lash the pushrod should collapse the plunger fifty thousandths of an inch.