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TR3 engine & box re-build


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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

 

Steves engine title3.jpg

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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 by Ian Vincent
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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

Newman PH1.jpg

Edited by BlueTR3A-5EKT
Learning to count!
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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

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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 by Lebro
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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

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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

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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

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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

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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.

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31 minutes ago, RAHTR4 said:

Hi Bob,

The differences between the collar types can be seen in the photo below

Regards, Richard

1.jpg

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.

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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 by Lebro
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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.

527495452_Valvespringmeasuremnt3.thumb.jpg.bfd45029ea6519fd70117a8b1f9df3fd.jpg  2106571425_Valvespringmeasuremnt2.thumb.jpg.75637ab214cbcb20c3d325574de5aa30.jpg  1335175364_Valvespringmeasuremnt1.thumb.jpg.9fb9f1aa7425a99ba710472c70d6b96a.jpg

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 by Lebro
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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.

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