"110# springs"
- Thread starter Texashighways
- Start date
Texashighways
Comp Diesel Sponsor
hahah, Jory, I am afraid you need to step up your protein intake or get some rogaine. .002?
As far as valve size that is relative to your setup. A good place to start is pressure X surface area =force. Look at the surface area of your valve multiply that times your boost or drive pressure, that will equal the force being applied to your valves trying to open against spring pressure. That is fairly straight forward and has nothing to do with nose pressure that has to keep all of the mass in check without float. The bigger tha valve, the more mass on the fast side of the valvetrain. That is why bigger valves try getting dished faces, hollow stems, undercut stems, Titanium retainers and locks etc. At a certain point there is so much mass in the valvetrain that a flat tappet will not support all of the pressure needed to keep it from floating at higher rpm.This is where people go to extreme pressures and kill the flat tappet cam, go to Titanium valves or take the easy road out and go roller with the HP penalty that ensues. If you really want to know how much spring pressure you need to counteract all of your mass, you will need to calculate all of your mass and factor for acceleration which is the change in lift per degree and jerk which is the change in acceleration per degree. Then you could have a good idea where you need to be spring wise. And don't forget that springs have mass too
If spring pressure is equal, choose a spring with less mass and a higher natural frequency.
As far as valve size that is relative to your setup. A good place to start is pressure X surface area =force. Look at the surface area of your valve multiply that times your boost or drive pressure, that will equal the force being applied to your valves trying to open against spring pressure. That is fairly straight forward and has nothing to do with nose pressure that has to keep all of the mass in check without float. The bigger tha valve, the more mass on the fast side of the valvetrain. That is why bigger valves try getting dished faces, hollow stems, undercut stems, Titanium retainers and locks etc. At a certain point there is so much mass in the valvetrain that a flat tappet will not support all of the pressure needed to keep it from floating at higher rpm.This is where people go to extreme pressures and kill the flat tappet cam, go to Titanium valves or take the easy road out and go roller with the HP penalty that ensues. If you really want to know how much spring pressure you need to counteract all of your mass, you will need to calculate all of your mass and factor for acceleration which is the change in lift per degree and jerk which is the change in acceleration per degree. Then you could have a good idea where you need to be spring wise. And don't forget that springs have mass too
If spring pressure is equal, choose a spring with less mass and a higher natural frequency.
murphy41
New member
Easy enough to figure out. Once surface area is measured, would it be better to multiply it by the higher pressure reading, whether it be boost or drive ? Say you use boost at 65psi and figure out force and get springs rated to support that. But drive is in the 70-75psi range. So taking the higher pressure number to get a force number would be the ideal way to go I assume? Or am I looking at this wrong? Once springs are picked its easy enough to get nose pressure numbers, and so.
Texashighways
Comp Diesel Sponsor
Exhaust valves are usually smaller on competition builds so that will offset the higher pressures in the exhaust. With 1.87" intake valves that are popular these days, there is 2.74 sq. in. 75 psi is not uncommon these days which would mean 206lbs pushing the valves open. This is why 60# springs don't cut the mustard. At full lift 206lbs of the nose pressure the rocker sees is being offset. Spring pressure is a big deal to power production on competition engines. On street trucks, too much is not cool.
Jory, I need a measurement on raccoon hair for posterities sake.
Jory, I need a measurement on raccoon hair for posterities sake.
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12vriviera
That Guy with that car
The sad part is, Zach can rattle all this off talking face to face, without blinking, pausing or otherwise.. lousy smart people!
4x4dually
Moderator
It isn't sad. It is actually nice to see a manufacturer explain stuff instead of giving everyone the "proprietary" bull crap. :clap:
I always learn something from Zachary's threads.
murphy41
New member
This is where I'm still learning to find that happy medium and not over kill the truck with too much spring. With a lot of the research I've been doing, your THE only one that's posted solid "understandable" information, without a sales pitch. Which is why I will be running your springs, cam, and pushrods with the current build.
And I second getting the Raccoon hair measurement...
Craig_C
Resident Smartass
See, you say there is 206lbs of pressure pushing the valve open....but you seem to be forgetting that there is pressure on the opposite side of that valve.
Intake stroke the valve is open, so pressure pushing it open only helps the valvetrain.
Compression stroke the pressure under the valve will go from near nothing to what, 5-600lbs?
Power stroke there is ALOT of pressure under the valve
And exhaust stroke there is still pressure in the cyl.
So with a 60psi spring, at what boost level would the valve actually push open, during actual engine operation, and not on a test bench with 0psi under the valve??
The way the logic in my head works, since drive pressure (aka backpressure) is usually higher than boost, the exhaust valve would be the valve more in danger of being pushed open, and this would only happen on the intake stroke.
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murphy41
New member
But the valve spring wouldn't be the component holding the valve open against that force. Wouldn't the rocker, pushrod, and cam be "holding" the valve open at full lift. Right ? And springs hold it closed against full boost/drive pressure.
Craig_C
Resident Smartass
True, if I understand what you are saying. But I am talking about needing heavier springs to keep the valves from being blown open.
Texashighways
Comp Diesel Sponsor
I will answer you at a later time, but I need you first to do some math for me. Please tell me how much pressure is on the other side of the valve and calculate the diminishing effects of this offsetting pressure.
I think two things will come of this
-your arguments have merit to a lesser degree
- you will struggle to fully find data as a function of rpm, factoring for boost/drive pressure, factoring for valve surface area, factoring for inertia and mass etc.
All that aside, practical application of simple concepts will take you a long way. That is my favorite tool, thought experiments using practical concepts. Sit on top of the piston and watch what is going on 42 times per second and then sit on the piston and watch the same thing at 15 times per second.
Craig_C
Resident Smartass
Im not all that good at math, just trying to bring up converstation!
And sitting on top of the piston....well thumping my noggin on the cyl head 42 times a second is prolly gonna hurt a bit!!
This is something that was brought up in a conversation by the ex owner of Total Engine Airflow....that guy knows a thing or two about the cylinder head area of an engine!