BlueTR3A-5EKT Posted November 25, 2020 Report Share Posted November 25, 2020 I cannot find the sheet I wrote it all on. It was well within the Newman requirements - something like under 100lb at fitted length, so the cam lobe load is less than that at the rocker due to ratio of 1.5. (push 100 at the cam = 150 at the valve spring.) This is the spec sheet I sent with that TR2 engine which the photo of the spring test is of. It forms the title page of an engine build photo book I produced. Those springs were as supplied by Classic & Modern on a rebuilt head. We will do brother's springs in a week or so and can report then on the springs used by Pete Burgess. Cheers Peter W Quote Link to post Share on other sites
Lebro Posted November 25, 2020 Author Report Share Posted November 25, 2020 (edited) The PH1 cam has .280 lift these days. No it doesn't - I was reading the duration of 280 ° 0.270" is correct Bob. Edited November 25, 2020 by Lebro Quote Link to post Share on other sites
Ian Vincent Posted November 25, 2020 Report Share Posted November 25, 2020 (edited) Just looking at your post Peter. If you have a cam ratio of 1.5:1 you need more shove at the pushrod end to achieve whatever you are trying to deliver at the valve end so whatever your valve spring compression force is, multiply by 1.5 for cam bearing pressure. And similarly, if your cam has .280" lift that translates to 0.420" at the business end. Rgds Ian Edited November 25, 2020 by Ian Vincent Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 25, 2020 Report Share Posted November 25, 2020 (edited) 1 hour ago, Lebro said: The PH1 cam has .280 lift these days. Where did I go wrong with my calculations? Quoted lift at valve is 0.405" Divide that by 1.5 and you get 0.270" Newman quote 0.270" lift at the cam See attached. Have we used the wrong rocker ratio? If you use 1.45 it comes to 0.280" (0.2793") 280 is the degrees duration. Advise please I fear my maths just went west. Peter W Edited November 25, 2020 by BlueTR3A-5EKT Learning to count! Quote Link to post Share on other sites
Ian Vincent Posted November 25, 2020 Report Share Posted November 25, 2020 Hi Peter, I’m not querying the rocker ratio, that is what it is but I was querying your calculation of the cam load. if you take moments about the point of rotation, the force on the short side multiplied by the length of that side must be equal to the force on the long side multiplied by the force on that side. So if one side is 1.5 times longer than the other, the force on the other side must be 1.5 times greater. Rgds Ian Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 25, 2020 Report Share Posted November 25, 2020 Thanks Ian Peter W Quote Link to post Share on other sites
Lebro Posted November 25, 2020 Author Report Share Posted November 25, 2020 (edited) See above for my correction I mistook Cam lift for duration(280°) my goof. Agree with Ian though, 100LB force on the springs would need 150LB on the cam. Your figure of 100LB seems a lot different to the 175LB I measured today with standard exhaust springs minus the third one. Was the spring compressed to equivalent of "max lift" (o.405") Bob. Edited November 25, 2020 by Lebro Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 25, 2020 Report Share Posted November 25, 2020 1 minute ago, Lebro said: See above for my correction I mistook Cam lift for duration(280°) my goof. Agree with Ian though, 100LB force on the springs would need 150LB on the cam. Bob. Yes I agree. My maths are wrong. The spring rate of under 100 still sets the load on the cam less than the Newman recommended. Peter W Quote Link to post Share on other sites
Lebro Posted November 25, 2020 Author Report Share Posted November 25, 2020 Was that 1 spring or double ? (& see my edit above) Bob. Quote Link to post Share on other sites
Ian Vincent Posted November 25, 2020 Report Share Posted November 25, 2020 FWIW I went for the same springs as you Peter, TR4a ones. They are quite soft but not a problem for me because I don't rev the engine hard. It has plenty of low down torque and delivers all the grunt I need at quite modest revs. Rgds Ian Quote Link to post Share on other sites
Lebro Posted November 25, 2020 Author Report Share Posted November 25, 2020 I did wonder about just fitting the outer spring, but could not think of a way to measure (I weigh too much !) Bob Quote Link to post Share on other sites
Ian Vincent Posted November 25, 2020 Report Share Posted November 25, 2020 11 minutes ago, Lebro said: Your figure of 100LB seems a lot different to the 175LB I measured today with standard exhaust springs minus the third one. Was the spring compressed to equivalent of "max lift" (o.405") Bob. You definitely don't want the third spring when you are using a Newman PH1 cam. If you do use it, you will almost certainly get coil binding on your exhaust valves. That is why I went for the TR4a valve springs and I picked up a set of S/H TR4a spring caps for not a lot of money from Revington. Rgds Ian Quote Link to post Share on other sites
Lebro Posted November 25, 2020 Author Report Share Posted November 25, 2020 How are the caps different for the later springs ? Quote Link to post Share on other sites
Ian Vincent Posted November 26, 2020 Report Share Posted November 26, 2020 I haven’t done a comparison but they have different part numbers. 105803 for the TR3 and 142137 for the later cars. Rgds Ian Quote Link to post Share on other sites
BlueTR3A-5EKT Posted November 26, 2020 Report Share Posted November 26, 2020 9 hours ago, Lebro said: How are the caps different for the later springs ? Spring diameters are different from the larger TR2-4 triple set up to the smaller diameter twins on late TR4& all 4A. Hence the caps have different diameter seat areas for the spring location. The collets do not change. Cheers Peter W Quote Link to post Share on other sites
Lebro Posted November 26, 2020 Author Report Share Posted November 26, 2020 Do you think it would be feasable to modify the earlier ones to fit the later springs ? Bob. Quote Link to post Share on other sites
Lebro Posted November 26, 2020 Author Report Share Posted November 26, 2020 Just been searching for info on here about valve springs etc, From Rogers experience the Moss "uprated" TR4A springs supplied with the new head he used were much stronger than his originals, which he reverted to using. The Moss current offering for 4 / 4A spring sets are described as "better than the original" - does this mean stronger, if so they are not what I need. is there any reason why I can't use only the outer spring from my existing TR3 set (I will attempt to measure the rate of that setup today.) Or, if not does anyone have a set of original rate TR4A springs / caps ? Bob. Quote Link to post Share on other sites
Ian Vincent Posted November 26, 2020 Report Share Posted November 26, 2020 I don’t see why not, you just need a set of the later springs for dimension purposes. After all you can buy alloy caps if you want extra bling so the strength required can’t be an issue. Rgds Ian Quote Link to post Share on other sites
Lebro Posted November 26, 2020 Author Report Share Posted November 26, 2020 Why would I need later springs if I were to use my TR3 outer springs only with my TR3 caps ? BoB Quote Link to post Share on other sites
RAHTR4 Posted November 26, 2020 Report Share Posted November 26, 2020 Hi Bob, The differences between the collar types can be seen in the photo below Regards, Richard Quote Link to post Share on other sites
Lebro Posted November 26, 2020 Author Report Share Posted November 26, 2020 Thanks Richard, smaller dia then. Bob Quote Link to post Share on other sites
John McCormack Posted November 26, 2020 Report Share Posted November 26, 2020 31 minutes ago, RAHTR4 said: Hi Bob, The differences between the collar types can be seen in the photo below Regards, Richard I had this problem with my long door low port head. I assumed I could use the collets from the high port head I was replacing, but it had been modified and had the 4A caps. Stuffed me around for ages as I couldn't find a supplier for the right collets. Quote Link to post Share on other sites
Lebro Posted November 26, 2020 Author Report Share Posted November 26, 2020 (edited) Ironicaly I have what you wanted, & you had what I may need ! To further this complex issue, if the late 4's & 4A's had smaller diameter springs, which it appears that they do, then presumably the spring seat machined into the cylinder head was also of a smaller diameter. If so an early head would really need a reducer of some kind ? Bob Edited November 26, 2020 by Lebro Quote Link to post Share on other sites
Lebro Posted November 26, 2020 Author Report Share Posted November 26, 2020 (edited) It's all gone very quiet ! Anyway, more measurements this morning. Removed springs, & setup to measure the force till coil bound using a luggage scale. The small spring came out at 53LB, & the large at just on the limit of the scale which is 110LB adding together = 163LB yesterdays tests gave 175 not a million miles out considering the crude method used. So the 2 BIG questions are: 1) Is 110LB a reasonable spring rate to use on a slightly tuned engine which won't be going above 5K, 2) Is using only 1 spring acceptable. A further thought - if either answer to above is "NO" the inner spring could be shortened by up to 1½ coils (at the bottom) & still leave it in compression when valve closed, this would reduce its rate considerably, but still act as a locating piece for the outer spring (if it needs one). I know I'm probably in uncharted waters here, but others opinions would be helpfull. Bob. Edited January 16, 2021 by Lebro Quote Link to post Share on other sites
Lebro Posted November 26, 2020 Author Report Share Posted November 26, 2020 Answered some of my questions (wonderful thing the internet) Double springs is a good idea because: 1) If one breaks, the other will prevent carnage 2) One spring rubbing against the other acts as a damper for oscillations A quick test on the lathe shows that my TR3 valve caps could easily be modified to take the 4A springs. The current Moss offering of these states that they are uprated - if this means high poundage then they are not what I need. Bob. Quote Link to post Share on other sites
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