Internal Combustion engine - evolution regarding parasitics

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The evolution of internal combustion engines, particularly the SB2 small block Chevy, involved significant design changes to improve performance and reduce parasitic drag. In the early 1990s, builders increased the cam bore diameter to 60mm for roller bearings, addressing camshaft twisting and optimizing timing in rear cylinders. This shift, along with the introduction of lightweight titanium valves, allowed engines to reach higher RPMs of up to 9000 while reducing valve spring pressures. The weight reduction from transitioning to titanium valves contributed to a notable decrease in reciprocating weight and parasitic drag. These advancements collectively resulted in a power increase of 30 to 50 HP over competitors.
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I wrote this a while back

Mechanical design - cam timing chain versus gear-driven (1 Viewer)​


  • Thread starterpnorm91
  • Start date Sep 12, 2013
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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