charlieb Posted April 24, 2009 Share Posted April 24, 2009 It has been mentioned before & in John's "Engine post mortem" thread that TT yellow valve springs (which I think are Kent?) are too strong. So what do people use with fast road cams? I remember GT mentioning Jag springs but there must be something more easily available, can you get away with standard springs? I'm interested in the 1500 but the same applies to other Triumph engines. Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted April 24, 2009 Share Posted April 24, 2009 Witor Springs seemed a sensible tension. Those Kent springs are WAY to hard. I was using some "terry" springs from the 60's, came off a Ford Crossflow 1500? Just use normal ones, check they dont go bound? I doubt reving to 6000rpm will stress them out, yes maybe 7000-7500. Link to comment Share on other sites More sharing options...
lordleonusa Posted April 25, 2009 Share Posted April 25, 2009 Witor Springs seemed a sensible tension. Those Kent springs are WAY to hard. I was using some "terry" springs from the 60's, came off a Ford Crossflow 1500? Just use normal ones, check they don't go bound? I doubt revving to 6000rpm will stress them out, yes maybe 7000-7500. I have purchased a set of Chris Witor's Valve Springs (red) to replace my TT1207 toilet tune springs (yellow) = 206 lbs & 35 lbs. I agree that these yellow springs are way too hard and cause undue wear on cam followers and valve seats. I had considered using the Jaguar Springs, but have been quite unable to source any original Jaguar Springs. (Jaguar AJ6 (1990-92, 4.0 Litre) Valve Springs: Part # EBC4871). The specification of valve springs is critical to the correct functioning of any engine. The spring rate is the amount of load the spring applies to close the valve. It has to cope with the weight of the valve and cap, and significantly, in a very brief space of time. At 6,000 rpm, each valve opens and closes 50 times per second. It also has to do so for the correct period of time as per camshaft requirements. Lastly, sufficient clamping pressure must be available to seal the combustion chamber while combustion takes place between 8 and 11: 1 compression ratios. The rates have to be kept as low as possible to reduce camshaft and follower (tappet) wear. The spring height and wire thickness enables a variety of camshaft profiles to be coped with. As you may notice from the figures above an uprated spring doesn't necessarily mean increased rate. A modern method in use to control valve closing is 'interference' valve springs, i.e. where there is friction between the inner and outer spring. This damps the valve movement without resorting to heavier springs. The springs and ratios listed are based on original specifications (including uprated springs) in use during production, (1967 to 1976), The critical areas are installed height to give 'closed' load and full lift load with adequate clearance to allow 'working clearance'. Coil binding is to be avoided at all costs, so allow a working clearance between coils, fully compressed of at least 0.030". Check when installed. Failure to check this at each valve could result in smashed springs, damaged rocker gear, damage to camshaft/followers, damage to rocker studs and locating studs - but more likely bent push rods. Don't recall exactly where those notes came from but they seem pertinent in this thread. L Link to comment Share on other sites More sharing options...
JohnD Posted April 25, 2009 Share Posted April 25, 2009 Using spring interference may be a desperate measure. The need for two springs is related to harmonics. A spring will have a base frequency, the one you hear if you strike it. Push that spring at that frequency and it will resonate, like a child on a swing, the response getting greater and greater as energy is added to the system in precise phase with the base frequency. Such base frequencies will be higher than the 50 cycles per second (Hertz) that leon quotes (50H is a low note, not the 'ting' of a struck spring) but as long as the base frequency is an exact multiple of the input frequency, this resonance will still occur. Push the child on the swing every two or three swings - it'll still go higher. If the spring's ocillation is being amplified by resonance, then it will not seat the valve correctly, as it will press it down then let it off as the sping contracts in it's own oscillation. A system of two springs of different base frequencies will have a base frequency that is the multiple of the two springs' frequencies. Thus the input frequency must be different and much higher to achieve resonance. I realise that this is different from damping - ideally, there should be damping in such an oscillating system to prevent the natural frequency being imposed on the output frequency. Interference springs can achieve this, but such springs are usually made from steel ribbon, rather than wire, so that the inner spring present s flat surface to the inner surface of the outer coil of wire. I've never seen a Triumph with springs like that. John Link to comment Share on other sites More sharing options...
spitNL Posted April 25, 2009 Share Posted April 25, 2009 To combat harmonics you could use a different spring design with no fixed harmonic frequency. Never seen one of these on a Triumph either, though. http://www.z4build.com/Base/Images/Products/350_BeehiveValveSprings.jpg Link to comment Share on other sites More sharing options...
charlieb Posted April 30, 2009 Author Share Posted April 30, 2009 Measured some used standard 1500 & TT yellow springs at my local machine shop today. Rate: Std: 330 lb/in TT: 219 lb/in TT quote 206+35=241 lb/in so mine may have weekened a little, unless TT are quoting load at compressed height not rate (they weren't clear) in which case its closer to the mark. edit: that last bit is crap! Pressure at install height of 34mm: Std: 37 lb TT: 70 lb Pressure at max lift 9.1mm (std cam 1.5:1 rockers) spring height 24.9mm: Std: 155 lb TT: 149 lb Pressure at max lift 11.0mm (R83 cam 1.5:1 rockers) spring height 23.0mm: Std: 180 lb TT: 165 lb So the std springs are stiffer than the TT springs but the TT springs are installed with a much greater preload. I presume the TT springs are weaker so as not to overload higher lift cams at max lift. This was not what I expected but I've never given any thought to valve springs before Link to comment Share on other sites More sharing options...
DaveNotSoSideways Posted April 30, 2009 Share Posted April 30, 2009 Do you really think there is any science gone into this? I wonder what original factory springs were?! Link to comment Share on other sites More sharing options...
Nick Jones Posted April 30, 2009 Share Posted April 30, 2009 Science? No. Lots of bs though. On my original 1200 engine (and the SAH head that followed), I had those funny push on valve caps and soft springs. That engine used rev to god-knows-what (no tacho, ignorance is bliss ;D) without valve bounce. Then, recently I saw someone working on the cylinder head of a modern sports bike with a redline somewhere in the low teens and that had single valve springs that looked like they'd come from a ballpoint pen - could compress them between finger and thumb. Ok, so the valves are pretty small and light but even so..... Presumably if you use lightweight tubular push rods, less spring pressure is needed. Trouble with installing springs with greater preload is that they will go soft quicker. I believe the TT ones are known for this? NIck Link to comment Share on other sites More sharing options...
lordleonusa Posted April 30, 2009 Share Posted April 30, 2009 I am about to dump my yellow toilet tune springs and fit the red witor ones. L Link to comment Share on other sites More sharing options...
GT6 Mike Posted May 1, 2009 Share Posted May 1, 2009 Originally fitted the Wittor / County red strpie springs with Wittor alloy seat for the inner spring. This worked fine but the engine wouldn't rev above 6750 rpm, checked the rate of various springs (yellow's / standard / red stripes) in different combinations, after several calculations I ended up with the red stripe springs and the original pressed steel spring seat, which in theory should have let me rev to 7300 rpm without losing control, actually now revs to 7400 so wasn't too far out. If using a high lift cam you will need to check that the springs are not going coil bound at max lift, I think this is the reason CW sells the inner alloy spring seats, increases the fitted / compressed length of each spring by approximatley 1mm. I have a chart somewhere of the various spring combinations measuring the spring force at fitted length (think I used 35mm) and max valve lift which I think from memory was 11mm, I'll try and sort it out. Link to comment Share on other sites More sharing options...
gt5r Posted May 1, 2009 Share Posted May 1, 2009 TT are crap - don't like county stuff - but probably best off the shelf road springs for budget though I've used Isky springs without a problem - not cheap - will hold 8000rpm + Pay your money http://iskycams.com/index.php Link to comment Share on other sites More sharing options...
GT6 Mike Posted May 1, 2009 Share Posted May 1, 2009 Spring Info Link to comment Share on other sites More sharing options...
willcolumbine Posted May 1, 2009 Share Posted May 1, 2009 Has anyone ever seen a broken standard valve spring? I bought a head a few years back and when I was stripping it down I discovered one of the outer springs was in two peices. What would cause that? Manufacturing fault? Link to comment Share on other sites More sharing options...
AJ.Lintern Posted May 1, 2009 Share Posted May 1, 2009 I suffered a broken valve spring in my Porsche - or rather my wallet did :'( I just hope the other 15 don't go the same way or I'll be thinking V8 transplants ;D Link to comment Share on other sites More sharing options...
charlieb Posted May 1, 2009 Author Share Posted May 1, 2009 Spring Info Thanks Mike that's great, I take it the ones you settled for are the green text, 46.5 lbs fitted, 138 lbs at 11mm lift? How did you decide how much force is enough? I ended up with the red stripe springs and the original pressed steel spring seat, which in theory should have let me rev to 7300 rpm without losing control How did you work that out? I wonder why the standard 1500 springs seem to be so much harder than your red springs which I understand are standard 6 cylinder jobs? Link to comment Share on other sites More sharing options...
gt5r Posted May 1, 2009 Share Posted May 1, 2009 So what do people use with fast road cams? Not a lot wrong with the standard OEM TR5/6 double springs Link to comment Share on other sites More sharing options...
Toby Posted May 1, 2009 Share Posted May 1, 2009 One of the springs broke on my Spitfire while in the fast lane on the M11... Link to comment Share on other sites More sharing options...
charlieb Posted May 1, 2009 Author Share Posted May 1, 2009 Ok I think I have a plan. What I need is a slight increase in seat pressure from the 37 lbs of the std springs but not as much as the TTs 70lbs. I also don't want the large increase in full lift (nose) pressure that the std springs would give if I shimmed them with my higher lift cam. So I can use the std outer springs with the TT inners: Springs Instal 34 Full lift std cam 9.1 Full lift R83 cam 11.0 Std 37 lb 155 lb 180 lb TT 70 lb 149 lb 165 lb Std/TT 50 lb 149 lb 170 lb Any flaws in my logic? Link to comment Share on other sites More sharing options...
lordleonusa Posted May 1, 2009 Share Posted May 1, 2009 Originally fitted the Witor / County red stripe springs with Witor alloy seat for the inner spring. This worked fine but the engine wouldn't rev above 6750 rpm, checked the rate of various springs (yellow's / standard / red stripes) in different combinations, after several calculations I ended up with the red stripe springs and the original pressed steel spring seat, which in theory should have let me rev to 7300 rpm without losing control, actually now revs to 7400 so wasn't too far out. If using a high lift cam you will need to check that the springs are not going coil bound at max lift, I think this is the reason CW sells the inner alloy spring seats, increases the fitted / compressed length of each spring by approximately 1mm. I have a chart somewhere of the various spring combinations measuring the spring force at fitted length (think I used 35mm) and max valve lift which I think from memory was 11mm, I'll try and sort it out. Please do, I will have to recheck my parts on hand, not sure if I have any of these mentioned inner alloy spring seats? L Link to comment Share on other sites More sharing options...
charlieb Posted May 1, 2009 Author Share Posted May 1, 2009 Leon, see reply no 11, very interesting (are we sad?) Link to comment Share on other sites More sharing options...
lordleonusa Posted May 1, 2009 Share Posted May 1, 2009 Spring Info Erm, I cannot see it. the attachment did not load L Link to comment Share on other sites More sharing options...
AJ.Lintern Posted May 1, 2009 Share Posted May 1, 2009 It's an Excel spreadsheet - you have to click the link to see it. Link to comment Share on other sites More sharing options...
charlieb Posted May 1, 2009 Author Share Posted May 1, 2009 Leon, you have mail. Link to comment Share on other sites More sharing options...
GT6 Mike Posted May 1, 2009 Share Posted May 1, 2009 Charlieb Measuring the springs and coming up with the various scenario's was fairly easy, I cant take credit for the predicted RPM limit for the setup I used. I work with some pretty talented engine development engineers who make it sound very easy when they do the calculations, I'll see if I can dig out the paperwok. Link to comment Share on other sites More sharing options...
lordleonusa Posted May 2, 2009 Share Posted May 2, 2009 Many thanks, and in the nick of time. I will be attending to my car in June. The head will be coming off for the first time since 2003. Major stuff. L Link to comment Share on other sites More sharing options...
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