Spring pressure and Lifter limit
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Spring pressure and Lifter limit What is the limit of stock lifters with the spring pressure needed for huge cams/lift.....3xx-4xx? LSx motors
Last edited by Spinmonster; Nov 5, 2005 at 11:45 PM.
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This is a very good question,i have always felt it was around 140 seat/350 open. I have friends/connections with access to latest technology who say it is much higher than once believed. Hi seat tension helps to give lifters the Fast Bleed action at low rpms, helping cam seem more driveable, at high rpms there isn't time for this bleed down allowing most of the lift and duration of the lobe design to be functional.
Im about to do a cam swap and thats the main thing im worried about. I want to run a 918, but the cost of thoes titanium retianers to go with them makes me want to run duals.
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Originally Posted by LSwonderfull
This is a very good question,i have always felt it was around 140 seat/350 open. I have friends/connections with access to latest technology who say it is much higher than once believed. Hi seat tension helps to give lifters the Fast Bleed action at low rpms, helping cam seem more driveable, at high rpms there isn't time for this bleed down allowing most of the lift and duration of the lobe design to be functional.
Personally, I'm partial to the sound of solids!
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Originally Posted by 383ss
who makes a spring with 450lb open and 140ish seat pressure? for an install of stock height?
He said 350 and what difference does it make what install height is used where lifter limits are concerned?
Originally Posted by Spinmonster
He said 350 and what difference does it make what install height is used where lifter limits are concerned?
he said 350? what are you talking about?
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Chris
Chris
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Originally Posted by MadBill
Ummm... Unless they're talking about the very latest lifter designs, that's contrary to what top tech writer David Vizard says. He has measured lift losses of up to one hundred thous on big cams with heavy springs! Some newer lifter designs, e.g. Morrel and the latest Crane, are apparently much better, due to extra-close tolerances and more particularly due to stiffer shells to resist leak-inducing distortion from the high side loadings of aggressive roller lobes. Even with light springs, there is always some bleed down, plus 0.006" to 0.010" or more due to compressibility of the small amount of air always entrained in the oil. Seems like a light spring together with the AFR Hydra Rev, which applies additional spring pressure direct to the lifter's outer shell, should be the way to go...
Personally, I'm partial to the sound of solids!
Personally, I'm partial to the sound of solids!
I have spent some time recently researching this by looking at valve train setups that have had lifter problems and those that have not including running high lift with heavy springs, using 1.8 rockers, etc. The conclusion I came to was that people seem to run up to 625 lbs. open pressure on the lifter successfully (spring pressure open times the rocker ratio), between 625 and around 650 or so start seeing intermittent lifter ticking and much more pressure seems to result in lifter failure. I have been assembling and plotting this information to guage what type of spring pressure I can run with my Crane 1.8's and the stock lifters by shimming the Crane 832's. Again, this is my own research based on doing searches here and on a couple of other forums but there does appear to be a trend developing.
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Thats interesting. The Comp. engineers i met at PRI show this year were convinced lift and duration bled down at high rpm effectively reducing cam specs. I always felt this happened at low rpm but had no idea it was a problem as you revved motor up. The way i understand it now is that we are giving up a good bit of power not running solid roller cams, even for street/strip combos.
