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I wrote this a while back
I have since found some new updates. Back in the early 1990s when the SB2 small block chevy engine was coming into play, they engine builders when to a 60mm cam bore diameter so commercially available roller bearings could be used. The reasoning was the camshaft was twisting during operation and timing was not optimum in the rear cylinders. Also the engine had a lot of parasitic drag from very high valve spring loading. About the max you could go was 8000 RPM with current 1990s technology. So they went to roller bearing camshafts and timing belts (see above old post )
Between these two changes you could pick up 30 to 50 HP over the competition. Later the engine builders went to super light weight titanium valves with 8 mm valve stems ( vs. 11/32" stems). You could up the RPM to 9000 RPM and run lighter valve spring pressures and still go 500 miles.
The weight difference between the old stainless steel 11/32" stem valve and titanium 8mm stem valves add up to reduction of over 1.6 pounds reciprocation and a reduction in contact are (parasitic drag) of .34" diameter reduced to .31 diameter times 16 valves.
Little things add up.
Mechanical design - cam timing chain versus gear-driven (1 Viewer)
- Thread starterpnorm91
- Start date Sep 12, 2013
I have since found some new updates. Back in the early 1990s when the SB2 small block chevy engine was coming into play, they engine builders when to a 60mm cam bore diameter so commercially available roller bearings could be used. The reasoning was the camshaft was twisting during operation and timing was not optimum in the rear cylinders. Also the engine had a lot of parasitic drag from very high valve spring loading. About the max you could go was 8000 RPM with current 1990s technology. So they went to roller bearing camshafts and timing belts (see above old post )
Mechanical design - cam timing chain versus gear-driven
Between these two changes you could pick up 30 to 50 HP over the competition. Later the engine builders went to super light weight titanium valves with 8 mm valve stems ( vs. 11/32" stems). You could up the RPM to 9000 RPM and run lighter valve spring pressures and still go 500 miles.
The weight difference between the old stainless steel 11/32" stem valve and titanium 8mm stem valves add up to reduction of over 1.6 pounds reciprocation and a reduction in contact are (parasitic drag) of .34" diameter reduced to .31 diameter times 16 valves.
Little things add up.
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