Different Spring rates intake and exhaust
01-14-2006, 11:32 AM
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Different Spring rates intake and exhaust Playing around with some numbers stock exaust valves have an area of about 1.88 sq inches. Intake have about 3.1 sq inches. Now For example lets use 7 psi of boost. That seven psi times 3.1 = 21.7 pounds trying to push the intake valve open. Some high mileage stock springs are barely holding 85 lbs
leaving 63.3 lbs seat pressure. about half of what is desired. Now the exhaust is different, most of us are probably running between a 2:1 and 3:1 pressure ratios. At 2:1 that would be 14 psi times 1.88 = 26 pound trying to open the exhaust valve, and at 3:1 its 21 psi times 1.88 = 40 lbs. So I'm looking at the Comp Cams springs 26915-16 @ 105 lbs and 26918-16 @ 130 lbs. I was thinking of running the 105's on the intake and the 130's on the exhuast, what do you guys think? Or just stick with one or the other?
leaving 63.3 lbs seat pressure. about half of what is desired. Now the exhaust is different, most of us are probably running between a 2:1 and 3:1 pressure ratios. At 2:1 that would be 14 psi times 1.88 = 26 pound trying to open the exhaust valve, and at 3:1 its 21 psi times 1.88 = 40 lbs. So I'm looking at the Comp Cams springs 26915-16 @ 105 lbs and 26918-16 @ 130 lbs. I was thinking of running the 105's on the intake and the 130's on the exhuast, what do you guys think? Or just stick with one or the other?
