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Valve spring pressures
Legitimate question, I am curious to what guys are running for spring pressures, on their big block marine hydraulic roller engines, and how many rpm you turn?
I have catalogs from crane, comp, lunati, crower, isky, elgin, howards, etc. When looking thru their books, most give a spring part number, to go with the cam. Across the board, it seems pretty common, to see a spring setup that comes in around 150ish closed, and 400-450 open pressure for a bbc hyd roller. For example, the every so popular crane "741" and "651" cams, are spec'd with a crane 99896 spring. Mine are setup at 165/450ish, pretty consistantly run 5500-5700 wide open, and turned to 6200 on the dyno with no signs of valve float. Icdedppl is running 225/575 on his crane 651 cams. I know the morel hi rev lifters call for that spring pressure, but , they also are supposed to support 7,000+ RPM, which he will never ever see. Besides avoiding loss of control, what is the purpose of running high spring pressures? And what are the negatives of too much pressure? Lets just say theoretically, a 160/460 would keep his valvetrain under control at 6000RPM, what benefit is there to having an extra 100psi of force over the nose, if it isnt needed? What's everyone running for springs? |
Im from the camp of less is more spring pressure wise , as long as maintains control at target rpm. Especially with a flat tappet. And lighter valvetrain components.
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Joe,
I'm not a cam or valve spring expert.... Spring pressures, installed heights, coil bind, lobe designs, ramp speeds, weight of the valve, retainers, psi on bottom side of intake valve are all considered ( meaning forced induction ) along with RPMs. It's a open question, all is specific to the build..... that goes along with pushrod wall thickness, tip material and material of pushrod.. My 525 build application; Isky 8205 plus spring, lightweight retainers @ 1.870 163# .070 from stack 470#, keep in mind, 3/8 valve stems "TREE STUMPS" if I had to replace 32 guides, I would of installed 11/32 valves with guides.in both engines... Do lighter weighted lifters help YES, like the Jessel's , the weight on the opposite side of the fulcrum of the rocker arm has to be considered, retainer, locks, valve weights. I have used a lot of titanium retainers over the years and bead locks, made from titanium.. same goes from valves used in BIG symmetrical port cylinder heads DART, Profiler 12, 14, 18 degree, stainless and inconel in those sizes equates to weight (MASS)... |
my 540's w/Dart Pro1 Alum. Heads are 155# closed, hyd. roller cams, no problems at all with mine,
Too much spring pressure puts stress on the complete valve train, beats up the valves , rocker arms, etc. much faster. |
Mine was set up for 200 closed and 600 open pressures when I redid my builds, I found out later that is not good for long term so when I had to fix some issues I took them down to 170 seat and about 560 open, hope I get some life out of it also have 680 lift I am worried about longevity now also...
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Any more spring pressure then needed is just bad. It is harder on seats, valves, push rods, lifters... It also takes away power with parasitic lose. Most hydraulic lifters will float over 450#'s
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I thought cams had matching springs?
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Originally Posted by MER Performance
(Post 4358993)
My 525 build application; Isky 8205 plus spring, lightweight retainers @ 1.870 163# .070 from stack 470#
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Great find.... Exactly as I said too much spring robs power. Mild when do you have time to work? you seem to spend a ton of time doing research, which is great for everyone on OSO but your wife must never get any time to .. well you know.... LOL
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Originally Posted by Bawana
(Post 4359689)
Great find.... Exactly as I said too much spring robs power. Mild when do you have time to work? you seem to spend a ton of time doing research, which is great for everyone on OSO but your wife must never get any time to .. well you know.... LOL
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Originally Posted by MILD THUNDER
(Post 4359709)
it doesnt take me long to get things done :)
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I run a moderate lift/ duration hyd. roller with 175-442 springs all i need to keep the valvetrain intact.we run for extended periods at 6k and above. My belief is that you must be able to close the valve gently enough not to damage it but with enough authority to keep in on the seat at higher RPMs I also believe that the closing pressure is engine specific to what you are trying to accomplish. I>E> n/a, turboed, Supered, NOS, etc. (as Mark expliained in his post)
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I run 190 seat/490 open but at 14 psi of boostwe are adding extra to acct for area of valve x boost trying to force intake open
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Originally Posted by 10x
(Post 1123714)
Yeah... That's what they all say, but only to extend the life of the lifter.
I tried 140# on the seat and about 385# at 600 lift, and with a mild (230-235) duration cam everything was fine till 5600 rpm. No matter what I did, the engines fell flat at 5800. End of the season I pulled the engines to make a few changes.When I lifted the heads to check the valve springs, cause I found signs of valve float, I found almost half of my valves were being pushed through the retainers. Some stems were flush with the locks. Bottoms of some of the roller rockers were hitting the retainers. What a F'n mess. Bottom line here is no one expects you to run more than 5450 rpm. I think that's what the mercruiser rev limiters are set for at the factory. When you start going over those rpm's, those light v/s combinations can't handle it. I had valve float so bad, it's a miracle i did'nt lose a valve. After many lenghty conversations with a marine (offshore) technication at Crane, he finally gave up the truth on spring pressures, rpm's and longivity of hyd. roller lifters. And if you want to turn 6000+ rpm's and make the bigger hp, you CAN'T expect your valve train and especially hyd rollers to last. It cuts their life in half, at the best. Now we run 175# on the seat, and 490# at 650 lift, and hav'nt had any valve train issue in 2 seasons.
Originally Posted by Reed Jensen
(Post 1131384)
There is a common misconception that the energy to compress the springs is lost.. not so.. the majority of it is returned on the back side of the camshaft. The energy that is lost is called hysterisis, which is internal friction in the spring itself. This is what causes the spring to heat up. If you were to graph the opening and closing rates on a linear graph.. then it becomes obvious that the valve is lifted off the seat, accelerated to full opening.. and then decelerated and slowly lowered onto the seat... The spring pressure isn't as big a factor on wear as you would think. But.. having the valve not follow the cam,,, the valve then "crashes" onto the seat.. This is much more damaging. Also it tends to hammer the keeper into the valve spring retainer. If you are using light weight retainers, they will begin to expand in the area of the keepers and quickly fail. Sometimes they will fail when not even running the engine hard. They have just give up and let the valve keepers slide through.
Mikes @ High Flow likes higher spring pressures, I forget his explanation but I trust his expertise. Your valves and seats are probably TIRED from all that bouncing around with that low seat pressure. |
Originally Posted by ICDEDPPL
(Post 4359726)
Mikes @ High Flow likes higher spring pressures, I forget his explanation but I trust his expertise. Your valves and seats are probably TIRED from all that bouncing around with that low seat pressure.
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Originally Posted by ICDEDPPL
(Post 4359726)
Mikes @ High Flow likes higher spring pressures, I forget his explanation but I trust his expertise. Your valves and seats are probably TIRED from all that bouncing around with that low seat pressure.
However, my cams are not overly aggressive lobes. I wouldnt try running .400+ lobes, 240* duration, and with light springs. Merc 525s have similar cams as me, and run less than 120lbs on the seat, and less than 400lbs open if i recall. My springs, a certainly not "light " in comparison to the majority of hyd roller springs out in the field that running successfully. While 6000 rpm is alot, its still a long way from 7500-8500rpm bbc stuff that gets built daily. When a cam has a big lobe, and short duration, the lifter wants to ski jump off the nose of the lobe much easier, so it needs lots of spring. These are things that separate a drag race camshaft profile, from an endurance engine camshaft. If it didnt matter, we would all be running .750 lift with little 240* duration cams. |
Originally Posted by abones
(Post 4359720)
I run a moderate lift/ duration hyd. roller with 175-442 springs all i need to keep the valvetrain intact.we run for extended periods at 6k and above. My belief is that you must be able to close the valve gently enough not to damage it but with enough authority to keep in on the seat at higher RPMs I also believe that the closing pressure is engine specific to what you are trying to accomplish. I>E> n/a, turboed, Supered, NOS, etc. (as Mark expliained in his post)
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Fyi, im not suggesting what i think is right or wrong. I can only attest to whats worked for me, and trying to see what has actually worked for others in the field, long term wise.
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Originally Posted by articfriends
(Post 4359724)
I run 190 seat/490 open but at 14 psi of boostwe are adding extra to acct for area of valve x boost trying to force intake open
This is what i'm refering to if you take away the 14# boost pressures would be 176/476, so we can't say what the perfect presure is for a hyd roller. it should be engine specific. |
Originally Posted by MILD THUNDER
(Post 4359732)
I can atttest to your boat being bad azz and runs !!!
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Heres another article on springs. He doesnt mention specifics, but he does mention any serious bbc drag racing engine, should have 220lbs of seat pressure. I dont know too many serious bbc drag racing engines that shift at 6000rpm these days though, or too many using a hydraulic lifter setup
http://rehermorrison.com/tech-talk-3...ngs-the-thing/ Another article where he mentions how a mild camshaft for an endurance engine, can have a smooth valvetrain, but wont win at the dragstrip. http://rehermorrison.com/tech-talk-4...n-revelations/ |
In response to whomever mentioned it, A lower rate spring does not close the valve easier.
===================================== An impact gun is effective because of the impacts/ blows, much more than the torque it has. Sure way to beat up your valve, valve seats, and rest of the valvetrain is too let it turn into an impact gun. ====================================== Valvesprings have mass. A lighter valvespring usually controls a valve better than a heavier spring, even if the heavier spring has a tad more pressure. ====================================== Only real negative effect a valvespring that has a little more prssure than yoiu actually need is increased heat from the valvespring itself. ====================================== Did you know that a valvesprings rate declines the hotter it gets and can/will go back to normal pressure when cooled off...obviously if you didn't beat the spring into submission. Therefore, your psi's may be a good amt less while running than you think. There's a chart I put up the other month on here, I forget where it is. |
Originally Posted by SB
(Post 4359824)
In response to whomever mentioned it, A lower rate spring does not close the valve easier.
===================================== An impact gun is effective because of the impacts/ blows, much more than the torque it has. Sure way to beat up your valve, valve seats, and rest of the valvetrain is too let it turn into an impact gun. ====================================== Valvesprings have mass. A lighter valvespring usually controls a valve better than a heavier spring, even if the heavier spring has a tad more pressure. ====================================== Only real negative effect a valvespring that has a little more prssure than yoiu actually need is increased heat from the valvespring itself. ====================================== Did you know that a valvesprings rate declines the hotter it gets and can/will go back to normal pressure when cooled off...obviously if you didn't beat the spring into submission. Therefore, your psi's may be a good amt less while running than you think. There's a chart I put up the other month on here, I forget where it is. |
Here's the sheet from PAC Springs that has a ton of info in it, including that of heat vs spring psi.
http://www.racingsprings.com/Multime...b/kb513103.pdf |
Originally Posted by SB
(Post 4359837)
Here's the sheet from PAC Springs that has a ton of info in it, including that of heat vs spring psi.
http://www.racingsprings.com/Multime...b/kb513103.pdf |
This is all way to much for me ... I am going to get some stock 330 hp motors, and just idle around.:rolleyes::rolleyes:
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Originally Posted by Bawana
(Post 4359865)
This is all way to much for me ... I am going to get some stock 330 hp motors, and just idle around.:rolleyes::rolleyes:
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In fact, too little spring pressure is almost always the root cause of valvetrain failures. We spent a year studying valve springs using an Optron, a sophisticated electronic device that can precisely record valve motion and reveal valve float. We learned some shocking truths about valvetrain behavior at high rpm. Even with a relatively mild camshaft profile, the valves bounce on their seats before they close. If the spring is too light, the valve bounces uncontrollably. The valve hits the seat, rebounds, hangs in the chamber awhile, and the bounces erratically several more times. Imagine how hard this is on the valve and the rest of the valvetrain! Once they heat up it`s probably more like 115, I think you need some spring oilers I like my spring pressure like a like my mountains.. HIGH! and I like my springs like I like my Beer .. COLD |
Ice - in fact, some manufacturers are starting to use deeper spring pockets and/or 'cages' (my term) for the lower prt of the springs to hold oil. Helps keep temps down and controls harmonics a little better. As most know now, Cup and some other forms of endurance racing go one step much further, and that is to 'flood' the valve covers with oil.
Your choice of having spring oilers can only help...that's for sure. |
Originally Posted by SB
(Post 4359943)
As most know now, Cup and some other forms of endurance racing go one step much further, and that is to 'flood' the valve covers with oil.
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I like what Reher says here.... "In my experience, an extremely smooth profile is unlikely to win drag races. It might be suitable for a NASCAR stock car engine or an endurance racing application...."
We're certainly not drag racing here and not stock car racing or endurance racing----but obviously the engines need to live/survive in everyday normal wear and tear......and I know I am not saying anything profound here, but what I have observed over the years is that aggressive valve opening/closings will hardly make any noticeable difference in a hi-perf offshore boat engine. |
I'm guessing that having a lifter out of adjustment (i.e. too loose) or collapsing would also hammer the valvetrain the same way that valve float would, since the clearance ramps can't do their jobs. Am I on the right track with my thinking?
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Originally Posted by ICDEDPPL
(Post 4359937)
See I told you your seats are getting beat up with that wimpy 140# pressure.
Once they heat up it`s probably more like 115, I think you need some spring oilers I like my spring pressure like a like my mountains.. HIGH! and I like my springs like I like my Beer .. COLD We can talk about high or low spring pressures all day, but whats high? Whats low? Whats high? For example, a GM truck big block, might have 90lbs of seat pressure. Merc 525's, had what like 120lbs of seat pressure? Crane/comp/howards/lunati, etc, normally seem to recommend anywhere from 140-160lbs of seat pressure on a bbc hyd roller off the shelf cam. Then all of a sudden, we are talking 225lbs of seat pressure, and nearly 600 over the nose on a hyd roller. At one time, that was serious solid roller spring territory. I guess its simply a guess, unless you take you engine combo to a spintron, and see what it really needs for adequate valvetrain control with your combination of parts. Or, take a chance, and tear it down after couple hundred hours, and see what things look like. Like seats, lobes, lifters, etc. I think most cam companies, do the majority of the testing for us, and hence why they may recommend xxx part number springs, with xxx cams. I am sure they arent pulling those numbers out of thin air. I certainly don't know more than the guys at crane, crower, or comp cams. I can only take their word for it. My guess is when you really start getting into stuff like 55mm+ cam cores, big body lifters, custom designed lobes, higher lifts, larger pushrod diameters, big valves, different valve materials, untraditional style springs, and so on, a trip to the spintron, is worth the money. My gut feeling, is a basic traditional, mild lobe, off the shelf hydraulic roller from crane, designed for marine applications, isn't requiring 600lbs of spring over the nose, at 6,000 RPMs, to keep the valve train under control. But, thats just a guess, and I certainly dont know that for sure. I do know, there are lots of guys who've ran those cams, with much less spring here on oso, for lots of hours without issue since the late 90's. |
Originally Posted by Keith Atlanta
(Post 4359976)
"flood the valve covers with oil" How can that have a positive effect for us? Wont that just cause more problems? Plus, cup cars are runnind a 2000++ RPM higher than we ever see.
Was not suggesting the Cup Car deal. |
Read Grumpy's response to the first question:
http://garage.grumpysperformance.com...gine-oil.6491/ Chris Osborn from PAC springs: http://speedtalk.com/forum/viewtopic.php?f=1&t=4595 |
Originally Posted by abones
(Post 4359736)
This is what i'm refering to if you take away the 14# boost pressures would be 176/476, so we can't say what the perfect presure is for a hyd roller. it should be engine specific.
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Originally Posted by MILD THUNDER
(Post 4360001)
Mine are 165 at the seat. Maybe this winter we will tear mine down, and see what things look like in there. But you're right on about the temps, that certain can change the pressures as the spring heats up. One of the reasons I cringe when i see guys saying "my oil temps are 260, but its ok, my 12 dollar a quart oil can take it". I dont care about the oil, I care about the engine parts!
We can talk about high or low spring pressures all day, but whats high? Whats low? Whats high? For example, a GM truck big block, might have 90lbs of seat pressure. Merc 525's, had what like 120lbs of seat pressure? Crane/comp/howards/lunati, etc, normally seem to recommend anywhere from 140-160lbs of seat pressure on a bbc hyd roller off the shelf cam. Then all of a sudden, we are talking 225lbs of seat pressure, and nearly 600 over the nose on a hyd roller. At one time, that was serious solid roller spring territory. I guess its simply a guess, unless you take you engine combo to a spintron, and see what it really needs for adequate valvetrain control with your combination of parts. Or, take a chance, and tear it down after couple hundred hours, and see what things look like. Like seats, lobes, lifters, etc. I think most cam companies, do the majority of the testing for us, and hence why they may recommend xxx part number springs, with xxx cams. I am sure they arent pulling those numbers out of thin air. I certainly don't know more than the guys at crane, crower, or comp cams. I can only take their word for it. My guess is when you really start getting into stuff like 55mm+ cam cores, big body lifters, custom designed lobes, higher lifts, larger pushrod diameters, big valves, different valve materials, untraditional style springs, and so on, a trip to the spintron, is worth the money. My gut feeling, is a basic traditional, mild lobe, off the shelf hydraulic roller from crane, designed for marine applications, isn't requiring 600lbs of spring over the nose, at 6,000 RPMs, to keep the valve train under control. But, thats just a guess, and I certainly dont know that for sure. I do know, there are lots of guys who've ran those cams, with much less spring here on oso, for lots of hours without issue since the late 90's. |
Originally Posted by KAAMA
(Post 4359985)
I like what Reher says here.... "In my experience, an extremely smooth profile is unlikely to win drag races. It might be suitable for a NASCAR stock car engine or an endurance racing application...."
We're certainly not drag racing here and not stock car racing or endurance racing----but obviously the engines need to live/survive in everyday normal wear and tear......and I know I am not saying anything profound here, but what I have observed over the years is that aggressive valve opening/closings will hardly make any noticeable difference in a hi-perf offshore boat engine. |
Great info from all parties here. If nothing else, great tech conversation :coolcowboy:
I don't know why I havent put spring oilers on yet, looks like another add on this winter coming |
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