high seat pressure or high open pressure?
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high seat pressure or high open pressure?
Looking at some .700-.750" lift applications, which is better? 220 seat and 675 open or 250 seat and 600 open. I was thinking lower seat and higher open, but i dont really know. What have you guys seen?
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flyin ryan
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Re: high seat pressure or high open pressure?
keep it up on the seat.dbusch wrote:Looking at some .700-.750" lift applications, which is better? 220 seat and 675 open or 250 seat and 600 open. I was thinking lower seat and higher open, but i dont really know. What have you guys seen?
Re: high seat pressure or high open pressure?
Well if it bounces off the seat you lose cylinder pressure
If it floats off the top of the lobe you gain cylinder pressure
Not a hard one to figure out.
If it floats off the top of the lobe you gain cylinder pressure
Not a hard one to figure out.
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David Redszus
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Re: high seat pressure or high open pressure?
The spring rate, free length, installed height, and lift will determine seat force and nose force.
What spring rate do you contemplate using?
Re: high seat pressure or high open pressure?
How aggressive are the ramps?
"Anyone who thinks the low RPM engine will be faster just does not have as much experience as the rest of us" -The late, great Joe Sherman.
You wont beat anyone if you do everything the same as everyone.
You wont beat anyone if you do everything the same as everyone.
Re: high seat pressure or high open pressure?
16 year old thread. He has probably changed cams twice in that engine and is now on his third engine combo by now. 
Paul
Paul
"It's a fine line between clever and stupid." David St. Hubbins
Re: high seat pressure or high open pressure?
David I would prefer to use an air spring actually. Just like F1
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David Redszus
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Re: high seat pressure or high open pressure?
The spring seat FORCE divided by the seat contact area equals the spring seat PRESSURE.
Suppose we have a 2.0" valve with a seat width of .063" and a seat force of 120 lbf.
The seat contact area would be 0.500 sqin, and the spring seat PRESSURE would be 240 lb/sqin.
When the valve is lifted off the seat, there is no spring PRESSURE although the spring
FORCE will increase with lift.
Determining the spring forces (seat and nose) are useful for understanding valve/lobe contact control.
Determining the seat pressure is useful for proper gas sealing of the valve.
Suppose we have a 2.0" valve with a seat width of .063" and a seat force of 120 lbf.
The seat contact area would be 0.500 sqin, and the spring seat PRESSURE would be 240 lb/sqin.
When the valve is lifted off the seat, there is no spring PRESSURE although the spring
FORCE will increase with lift.
Determining the spring forces (seat and nose) are useful for understanding valve/lobe contact control.
Determining the seat pressure is useful for proper gas sealing of the valve.
Re: high seat pressure or high open pressure?
Being in control of the valvetrain is critical, and as mentioned earlier in this thread years ago, "lofting" the valves can increase flow just like a larger cam and it needs to land "in control" which generally requires more seat pressure.
Heat is energy, energy is horsepower...but you gotta control the heat.
-Carl
-Carl