12 valve seat pressure

95cummins5.9

95cummins5.9

Old man ***** gossiper
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Jun 18, 2012
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What is a good closed pressure to shoot for? I am in the process of redoing my head, currently have a manely dual valve spring that was used in the old head. They had shims under the springs and I want to avoid that if possible. I have a haisely style keeper and a manely keeper, they are .050" height difference.

This engine turns 4200 rpm max with 55-60 pounds of boost. Street driven, stock cam

Please don't bust my balls too hard, I did search.
Thanks for your time.
 
That's kind of a loaded question. Install height is normally 1.900 on a stock length valve. You need to know what the spring pressure is there. Why do you want to avoid shims?? That's what changes the spring pressure. You need to check the install height on the valve with no spring on it to see how close it is to the 1.900 and go from there. You also have to be careful with to much open pressure on a stock cam because it will start to wear out the cast cam. I would be more worried about open pressure then seat.
 
FYI, seat pressure on 60lb valve springs is ~155lbs IIRC. It took me forever to find it when I was building my motor. The machine shop kept talking about watching the nose pressure on the cam, which would be the same as the open pressure? They couldn't explain it very well, but basically the cam wears into the block if it is too high.
 
So whats seat pressure of 150# springs if 60lbs are 155?

And who has actual experience with aftermarket springs damaging the block or the cam on a street truck?

Are all us performance seekers taking a risk bolting up different springs.?
 
hydroshok said:
FYI, seat pressure on 60lb valve springs is ~155lbs IIRC. It took me forever to find it when I was building my motor. The machine shop kept talking about watching the nose pressure on the cam, which would be the same as the open pressure? They couldn't explain it very well, but basically the cam wears into the block if it is too high.
Click to expand...

Nose pressure would be the spring pressure the cam is seeing at full valve lift. So you need to know valve installed height, max lift of your cam, add your rocker ratio, than compress the spring to that height. This will be your over the nose pressure.
 
Last edited:
Lucas1 said:
So whats seat pressure of 150# springs if 60lbs are 155?

And who has actual experience with aftermarket springs damaging the block or the cam on a street truck?

Are all us performance seekers taking a risk bolting up different springs.?
Click to expand...

150# springs would be 150# seat pressure the 60lbs springs get there name due to being 60lbs more seat pressure than a stock valve.
 
Info I could find:

60lb Intake & Exhaust Valve Springs 89-98 12 Valve Dodge 5.9L Cummins
The seat pressure on these springs is ~115lbs at the installed height of 1.950.
At 400 lift, the spring pressure is ~192-195lbs.
At 500 lift, the spring pressure is ~210lbs.

The factory spring pocket measures about 1.410" ID
Factory Installed Height 1.88-1.9 with stock valve
Stock style seals measure about .750" OD


http://www.competitiondiesel.com/forums/showthread.php?t=145521

http://www.puredieselpower.com/catalog/60lb-intake-exhaust-valve-springs-8998-12v-dodge-cummins-p-633.html
 
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