Re: Pushrods
Valvetrain geometry is spot on if the rocker contact point is at the center of the valve stem at half lift. Of course this will vary somewhat with deck height tolerance and gasket thickness, and it may vary quite a bit if the decks and heads are machined for maximum compression. That's why some race engines use different than OE length pushrods to correct the geometry. In fact you can have pushrods made to your specified length.
For most road engine rebuilds that don't involve significant material removal, the geometry is probably okay, but it should be checked prior to buttoning up the engine.
The rocker "rolls" across the valvestem if the radius of the tip is the same at the distance from the fulcrum to the center of the tip.
The limitation of the OE stamped rockers is when sustained revs over 5000 is normal service, which can cause the balls/rockers to burn/gall. This was a problem with the early Trans-Am engines since the normal rev range was 5000-8000 with stiffer than OE valve springs, and it's a problem with vintage racers where the rules require OE rocker arms, but for a road engine, even one that will occasionally see 7000+ revs, the OE rockers are simple, light weight, and pretty much bulletproof.
As a historical footnote, it was Pontiac that came up with the stamped rocker/ball design for their new V8 that went into production concurrently with the Chevy small block for the 1955 model year. Ed Cole "borrowed" the design for the SB, and for all but the most highly tuned racing engines, it's a simple, inexpensive, elegant design.
Duke
Valvetrain geometry is spot on if the rocker contact point is at the center of the valve stem at half lift. Of course this will vary somewhat with deck height tolerance and gasket thickness, and it may vary quite a bit if the decks and heads are machined for maximum compression. That's why some race engines use different than OE length pushrods to correct the geometry. In fact you can have pushrods made to your specified length.
For most road engine rebuilds that don't involve significant material removal, the geometry is probably okay, but it should be checked prior to buttoning up the engine.
The rocker "rolls" across the valvestem if the radius of the tip is the same at the distance from the fulcrum to the center of the tip.
The limitation of the OE stamped rockers is when sustained revs over 5000 is normal service, which can cause the balls/rockers to burn/gall. This was a problem with the early Trans-Am engines since the normal rev range was 5000-8000 with stiffer than OE valve springs, and it's a problem with vintage racers where the rules require OE rocker arms, but for a road engine, even one that will occasionally see 7000+ revs, the OE rockers are simple, light weight, and pretty much bulletproof.
As a historical footnote, it was Pontiac that came up with the stamped rocker/ball design for their new V8 that went into production concurrently with the Chevy small block for the 1955 model year. Ed Cole "borrowed" the design for the SB, and for all but the most highly tuned racing engines, it's a simple, inexpensive, elegant design.
Duke
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