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Old 11-20-2008, 07:33 AM
How fast is fast enough?
 
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Hyd. Roller cam question

What is the recomended maximum spring pressure for hyd. roller lifters? Standard chevy .842". I'm being recomended valve springs with 190 pounds of seat pressure and that seems a bit high.

Does anyone have expierence with this? What is the most spring pressure anyone has ran on hyd. roller lifters?

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Old 11-20-2008, 02:33 PM
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That does seem a bit high, I think I recall that 170#s was about the max to stay reliable. What is the open seat pressure? If your using a mild cam you may be ok, but if your going max lift I think I'd steer towards something a little softer. Lunati makes a solid roller that will stand up to just about anything you can throw at it.
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Old 11-20-2008, 02:55 PM
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They have another rec. for one with 170, but I won't be able to run 1.7 rockers, I'll just stick with 1.6's and go that route I think. I'll be running .595" with 1.6 rockers, which is probably more than I need anyway.
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Old 11-20-2008, 03:13 PM
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There's an article in October 2007 CarCraft where they did a 3-way cam shootout, Hyd F/T, Hyd Roller & Solid Roller with close to the same specs taking in to account for lash etc. Steve Brule' from Westech reccomends>>
Lifter Style-------Seat Pressure-------Open Pressure---Camshaft----------
Hyd F/T* ------------150*--------------350*----------284XE F/T*-------
Hyd Roller-----------200---------------400------------294XE roller--------
Solid Roller----------220---------------575------------286XER Mech. Roll
Too much spring pressure does not really force the hydraulic lifter piston down as commonly thought. What really happens is that higher spring pressures tend to deflect the pushrod, which causes valvetrain separation at higher engine speeds when the pushrod pole vaults the valve past the nose of the cam. This clearance in the valvetrain allows the lifter piston to pump up. .080" wall pushrods are needed.
*After Cam breakin.* It is advisable to remove the inner spring on any dual-spring package when breaking in a new F/T cam. Not neccesary with rollers.*
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Old 11-20-2008, 03:19 PM
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Ap72, those 170# will be fine , it'll take a little load off those needle bearing & pushrods. #'s above are more for race/dyno setup anyway.
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Old 11-20-2008, 03:42 PM
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Ok, that really helps relieve some pressure (no pun intended). I never heard of a standard for hyd. rollers but I knew what hyd. flatties were maxed out at and I was afraid that due to their simmilar design it would be the same. Also the standard "roller cam" spring packages were coming in with around 130 seat pressures and it kind of made me think i was getting into solid roller territory.
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Old 11-21-2008, 04:54 AM
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springs

There is way more to chosing the correct spring for a hyd roller then just seat pressure. Hyd rollers are fussy about the rate of the spring. What you need is a spring that is light enough at the seat to keep the rollers from clacking at idle but at the same time control the heavy valve train at higher RPM'S.


Keith
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Old 11-21-2008, 06:32 AM
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Well, i trust they know what they're doing when they spec me a set of springs, I was just worried about them being to stiff.
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Old 11-21-2008, 08:07 AM
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springs

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Originally Posted by ap72
Well, i trust they know what they're doing when they spec me a set of springs, I was just worried about them being to stiff.

If you trust them why did you ask???
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Old 11-21-2008, 08:37 AM
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It never hurts to ask. Besides, its good to have a guideline for future reference.
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Old 11-22-2008, 05:20 AM
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Spring Rate

Spring Rate is very important. The spring rate is the amount of load in pounds created for every inch on travel the spring is compressed. If you know the load at both the closed and open points, you can determine the rate. Subtract the installed load from the open load and then multiply by the lift ratio. (lift ratio = 1 divided by the max valve lift). Using Comp 939 springs as an example: 420 - 167 = 253 X 1.85 [1/0.540lift = 1.85] = 468 pounds per inch (lb/in) spring rate.
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Old 11-22-2008, 08:48 AM
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What RPM range do you have in mind for this engine? I'm running 155 on the seat and 340 open with a comp XE282R and 1.6 rockers in a boat and I think that is too much, if I could find springs that fit my heads with about 130 on the seat and 320 open I'd use those. Who is recommending the 190 pound springs, the cam company or the machine shop?
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Old 11-22-2008, 09:36 AM
How fast is fast enough?
 
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the cam company. Its a cam with considerabley steep lobes though, 1.6 rockers are compounding the problem. I'll be at .595" lift at 242 duration at .050".
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Old 11-23-2008, 11:20 AM
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Generalizations are OK, but remember that the rocker arm ratio multiplies the spring pressure to the lifter.

Stock factory hydraulic roller lifters should be limited to 300# over the nose actual spring pressure.

When lightening the valve train components a little goes a long way towards valve control.

Just because a lifter will run at a specific poundage doesn't mean that it will control pushrod deflection, rocker arm deflection, roller bounce, and/or LAST with all that pressure on the roller bearing.

I'd almost bet that the cam company did not ask you about valve weights, pushrods, etc... and that they gave you a catch-all spring rate to make sure all the variables are covered. Even if it wears out your lifter bearings.

Always keep in mind is that when spring pressures get high, so does replacement maintenance. Springs wear out, roller lifter bearings wear out, rocker arm trunion bearings wear out, push rods wear/deflect. Many of those high power engines won't run 7,000 street miles without replacement maintenance.

JMO

Last edited by ScoTFrenzel; 11-23-2008 at 11:36 AM.
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