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SBC roller cam

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dreracecar:
WAY over- thinking this :o

Roller speed is reduced by using a small base circle
Sky high spring pressure has more effect on twist then a slightly smaller shaft dia. and is why you go with the tool steel billet material.
 I broke 2  small base cams over the years and both at the same spot (#8 exhaust), just bad material for the cores, went to a tool steel and never another problem

Roger:
Over-thinking? This is what happens when you’re retired and have time on your hands while you’re waiting for your turn in the chassis shop. Or maybe I’ve been hanging around some NHRA comp eliminator guys too much :)

I agree that roller speed is reduced with a small base circle cam but the reduced base circle increases the ramp acceleration rate of the lobe resulting in an increased unit load for cams as compared with a regular base circle with the same specs. For example, at some point during the intake cycle we find the lobe has raised the lifter 0.300”. If you have a regular base circle cam and move the cam 1 additional degree, we might find the lifter has now risen to 0.310”. If we take a reduced base circle cam and move it 1 additional degree we might find it has raised the lifter 0.320” along with an accompanying increase in spring pressure compared to the regular base circle. The same overall load exists on both cams but the reduced base circle has less area (rotations) to disperse that same load so the load per revolution will be higher. At least that’s my understanding.

dreracecar:
I have lunch with Ed Iskedarian every day, I ask him

Roger:
Great! I’m sure The Camfather will have some good input. And if you & he have time, ask him about the valve timing for a 383 SBC with 13.9-1 compression making 530# @ 5200rpm and 615hp @ 7200rpm. The fly in the ointment here is that this N/A gas burning engine will use zoomie headers. Can’t run collector headers, it’s against my religion. Not trying to make up all the horse power lost using zoomies with the valve timing, just trying to minimize the loss with proper valve timing for my application.

ricardo1967:

--- Quote from: Roger on August 18, 2016, 12:34:28 PM ---Great! I’m sure The Camfather will have some good input. And if you & he have time, ask him about the valve timing for a 383 SBC with 13.9-1 compression making 530# @ 5200rpm and 615hp @ 7200rpm. The fly in the ointment here is that this N/A gas burning engine will use zoomie headers. Can’t run collector headers, it’s against my religion. Not trying to make up all the horse power lost using zoomies with the valve timing, just trying to minimize the loss with proper valve timing for my application.

--- End quote ---

We share religion ;). Of course I respect all denominations though.

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