Thread: Cam Lift?

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I was wondering how much of cam lift a 350 with stock heads and Z28 valve springs can handle?

Related to this topic I have a question for Tech1. I now have a Crane 10010 cam in my 350 with specs: 194/204 @0.050" and 260/270 duration, the lift with 1.5 ratio rockers is 0.398"/0.420". My question has to do with what happens if I add 1.6 ratio roller tipped rockers. I note in the flow studies given at the site below:

http://chevyhiperformance.com/techarticles/41598/

that the peak flow in my 882 GM heads peaks out at about 0.400 valve lift on intake so the cam already meets that at top lift. On the other hand with 1.6 ratio rockers the lift will be 0.424"/0.448" which is beyond the peak flow of the heads. Still if the valves go beyond the flow limit on the way up and the way down the valve will be open a little longer and the total flow should be greater? Assuming a linear change in the duration at 0.050" (because I do not know the curved shape of the cam ramp at 0.050"), I get a new lift of about 0.053" at 194/204 so the duration at 0.050" will be longer, but not much; maybe at most 199/205 so I will end up with a higher lift, short duration cam. This will hurt mileage a little but the question is will this hurt or help torque in the 2000 rpm range? The static compression ratio is about 8.9:1 and I have Z28 springs as per the question above. I realize you need to know the shape of the 0.050" ramp on the cam to determine the new duration but I doubt if it is more than 5 degrees? Bottom line, will this help or hurt low rpm torque?

Don Shillady
Retired Scientist/teen rodder