Just curious what your thoughts are on hp to collapse a spring. I see that they are making single coiled valve springs that will go up to .600 lift. Would it be better to use a dual spring on a roller or use one that doesn't require as much energy to open? BTW, the cam is roughly around .600 lift give or take...
Root, I prefer a single spring with a damper. But I'm not running that much lift on anything I got. If you can get a single spring that is the right spring rate to go with your cam I think that's what you should do. Of course that's just my opinion. I don't have anything scientific to back it up.
I have NO idea if this is based on ANY scientific evidence or not, but it makes sense in my little brain: If you have one spring, to control the weight of a specific valve, and up to a specific rpm, and then put a Double spring, to handle the SAME weight and RPM, then in theory, each spring of the dual pack would be working half as hard, and therefor would last twice as long. Does that sound anywhere close to reasonable to any of you more scientific types? :
It seems to me that you always want to use the least force that will acomplish the task. If a single spring will return the valve quick enough it will perform the task with the least damage to the rest of the valve train and minimize recipicating weight. Dual springs will close the valve faster by exerting more force, but that force is transmitted to the cam as well as the valve face and seat. Desmotronic valve systems like my Ducati do away with valve springs by using a set of lifters to open and close the valves eliminating wear on the cam shaft as well as eliminating weight from the valve train. This system allows for no valve float at any RPM and is why some of the racing twins are running upwards of 16000 RPM. Back to cars motors, my opinion is to use a single spring if it will accomidate both the lift and rpm desired. I am sure there are some people here that can give you a more accurate answer but thought I would throw in my 2 cents worth.
Well see, I was kinda thinking along the same lines, except for this: If a 200 lb/in spring will handle the valve motion, wouldn't TWO 100lb springs do the same, only more efficiently?
I think it's got a lot more to do with RPM range rather than HP. I think it's also got a lot to do with how long the spring will last, dual springs will hold up a lot longer than a single spring will. If it's for a street car dual springs are the way to go.
The valve doesn't know how many springs your running. Only how stiff the springs are,and how far/fast your trying to move it. Lower tension springs will last longer for a given amount of deflection. If you need double or triple springs to get enough tension,so be it. The weight of the springs is almost insignifigant.
The new beehive springs seem to have potential. GM used them on the latest series of motors, and one of the bigger cam outfits has used them as retrofits in earlier motors. From what I read, the shape of the spring makes it self-damping, and valvetrain weight is reduced due to the smaller retainer. It seems to me to be at least worth asking the question to someone with dyno experience on various spring packages.
Another problem you are confronted with,on a higher RPM, higher lift,roller cam,is valve "bounce". The combination spring pressure and closing ramp on tha camshaft,can actually make the valve bounce back open after the valve hits the seat.... Call the camshaft manufacturer and see what THEY recommend
[ QUOTE ] I'm not sure what I believe now...... I'm gonna make a call. [/ QUOTE ] OK be that way. And let us know the skinny. OK?
[ QUOTE ] The new beehive springs seem to have potential. [/ QUOTE ] new? new? hahahaha i have a set of '64 Oldsmobile heads out in the garage with beehive springs on'em from the factory!
I like the comment about two springs equaling the pressure required to run a specific valve train combo at a particular (high) RPM. Very true and like was said, less heat was generated. That said, little brother ran single valve springs on his 500 CID DRCE engine. Shift points were 9200 RPM and he broke a valve spring almost every run. Good quality springs in fact. When he went to a double spring setup that was the end of the problem. The problem being harmonics. Very high speed motion pictures show single springs suffering a series of standing waves that run up and down the spring at varying times. The standing waves - call em vibration to make it easy - broke the springs from simple fatigue. Aside from harmonics, the simple operation of the spring - single or double or single with damper - creates heat. An important consideration for circle burners and especially for NASCAR engines. Said NASCAR engines most times run a spray bar to get a cooling shower of oil over the springs. Harmonics can be very damaging to engines and it doesn't always happen with valve springs. Little brother ran a 498" alcohol 455 Olds stoker once upon a used to wuz, shifted around 6800 RPM and destroyed the engine due to crankshaft harmonics. He ran a simple hub - mainly for timing since the water pump and fan was driven by a small electric motor utilizing a Gilmer belt. He shoulda been running an SFI approved damper, but elected not to. Never have I seen a more destroyed engine. Aside from breaking the crank in to several pieces, the cam was broken and the magneto was blown off the engine and hanging by the plug wires. The only things salvaged were the Batten heads and mechanical fuel injection setup. He got a cool bent aluminum rod out of the deal. Made for a heck of a souvenir....
I have had good results with double springs. Isky cam,flat solids,and double springs. I ran this combo in the early 80's with a 283. Hit almost 9000 rpm a couple of times It skeered me! Sparky
Every spring has a harmonic frequency at which point it will stay compressed even though there is no pressure being applied to it. if a strobe light is used to illuminate a spring during operation and the rpm is increased there will be a point where the spring will seem to stand compressed (it's harmonic frequency). When this happens the spring can no longer control the valve motion. Now pair this spring with one of a different frequency (rpm) and they will cancel each other out and allow the valve motion to continue as per specs. The flat wound inner spring found on any small block Chevy spring is an attempt to dampen that harmonic frequency without resorting to a second spring. Frank
Should have added. CONSULT YOUR CAM GRINDER FOR CORRECT APPLICATION They designed the cam and ALWAYS have spring specs. for each grind. Bench racing and the recommendation of a friend of a friend is the WORST way to pick valve train hardware. Frank
Lotsa truth here. Harmonics are the enemy of any valvespring, and I've seen the same video C( mentioned showing harmonic distortions traveling up and down a coiled valvespring in action. Its also been proven that by running dual springs with differing harmonics, they serve to offset the effects of these harmonics and act as a "shock absorber" of sorts. I choose to run the lightest-possible valve spring capable of doing the job. Overkill springs simply cost power to push. I always talk to a couple cam and spring guys about my choices and get their ideas. Interestingly, we almost always agree on the call. The "right" springs are certainly out there today, as mfrs have been researching them almost more than any other engine component. Once known to be the weakest link in any racing engine, but especially in endurance racing engines, much attention was drawn to them. After extensive research into materials, thicknesses, lengths, and even wire wrapping technique, todays modern performance valve springs (including the beehive springs mentioned earlier), are better and more durable than ever. Do the homework and pay for a good set of springs. The right choice means you'll never have to think about it until the next rebuild...which should be many miles and many smiles down the road. Scotch!~
The new Beehive springs also have a unique wire cross section: it's oval. The wire is wider than it is tall. This lets you run more lift before hitting coil bind, which is another aspect needed to consider when choosing springs. Dual springs will have less coils, or winds, so there is more space between the coils--allowing more lift before hitting coil bind. To explain that, if you have a two inch tall spring, and one has only 4 coils, there would be 1/2-inch between coils. If that 2-inch tall spring had 8 coils, then you'd only have 1/4-inch between coils. (Those numbers are just for easy reading--not an actual spring example). Another thing stiff springs do is keep the valves from floating at higher rpm--that's pretty much all valve float is; the valves fly open, and hang open for an instant because there isn't enough spring to overcome the speed of the cam throwing the valve open. A writer I respect a whole lot as being able to do most anything didn't grasp that, which surprised the hell out of me. He'd install swap meet springs in his motors! On one engine, after he learned about blueprinting spring pressures, he picked up 500rpm and a bunch of horsepower, by simply matching springs to the cam. He attributed his valve float problems to the heavy mass of stainless steel roller rockers and heavy keepers, etc. The inertia generated by heavy valve train parts should be any consideration unless you're running a Pro class in racing or an endurance engine. Now's a good time to talk about blueprinting the valve springs, too--most wiped out cam lobes are caused by valve springs being screwed up. Grab a set of brand new springs, and compress each of them to "X" inches (your installed height). It's common for there to be a variance in pressure by as much as ten pounds or more, across all 16 valves. Now, the more you compress a spring, the more pressure it has. So if you've got one seat pocket that isn't cut quite as deep as the others, there won't be as much space between the spring pocket and the valve tip (this is your installed height), so the spring is going to go in a shorter space than the valve next. The spring is compressed more, and therefore generates more seat pressure. With a set of heads with sloppy machine work, you could easily get the installed height so wrong that you've got maybe 50 more pounds of seat pressure than you're supposed to. Now draw the short straw and install your stiffest spring in the shortest pocket, and you could have 80 pounds or more too much seat pressure! I've seen it. Too much seat pressure equals a dead cam lobe. -Brad
[ QUOTE ] C-9,What setup was it on the OLDS engines that featured rotators in their valvetrain? [/ QUOTE ] 70-72 Olds. The rotater looks like a fat/thick retainer. It has a sprag-like device inside the retainer looking goody to rotate the valve at different points in the spring cycle.
Don't forget that the stiffer springs are much harder on the valves..OK if you tear down a lot but not so good on a daily driver.
Olds used beehives as early as '58. They were having break-in problems in '57, so switched. So I was told by an OCA member, and I have seen the beehives on the '58 heads. Current beehives are surely superior! Here's the theory, as far as I understand it: With a high lift cam and a squareish lobe from lots of high-lift duration, at high RPM the valve wants to hang in the air and can't retract quick enough. Well, that's what stiff springs and high spring pressures do-- get it back quickly. Trouble is, the normal valve spring is stiff through and through, and it winds up slamming the valve back really hard. Also has a lot of seat pressure. This tends to cause a valve job to go away sooner. The beehive is supposed to be really stiff at full lift to start the valve moving ASAP, but then to get a little gentler so as to not slam the valve into the seat quite as hard or to have excess spring pressure. At least that's my understanding. Anyone have different theories?
Actually, it seems to me that the guys at COMP did tell me that as well--makes it sort of a variable-rate spring, that is tunable. -Brad
[ QUOTE ] makes it sort of a variable-rate spring [/ QUOTE ] Kinda like progressively wound coil springs for suspension? Always wondered why valve springs weren't wound that way... Ahhh, just get solenoids to actuate your valves!
Yeah, exactly like progressively wound suspension springs. I used that same analogy with their valve spring guy. COMP's cam engineer is a trained nuclear physicist. The guy across the hall from him designs the valve springs. New spring comes out, the physicist designs a cam lobe profile that will break the spring. Spring guy designs a new spring, and it never ends. I was WAY out of my league talking with those guys!!! Fortunately, they were able to dumb it down a lot for me--and the posts here sorta kick-started it back up. -Brad
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