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MG TD TF 1500 - valve spring length

Hello,
Changing my valve seals today. Quite a tricky affair !

I was wondering about the springs. There seems to be a standard type and an extra-strong type for Stage II tuning.

It is impossible to test the spring without a special bench. And the uncompressed length is not indicated on the workshop manuel.

Does someone know the standard spring length.

My free length measurements read :
Inner : 71 mm
Outer : 77 mm

What type of spring is it ?
Laurent.






LC Laurent31

I am rebuilding a early TD engine, I do not know if the springs are the earlier or later springs, but they do measure the same as yours.
My customer has requested a Roller camshaft, so if any one needs the springs, lower locators, or oil deflectors, I will send for only the cost of postage from NY USA.
laf48@aol.com
914 420 8699
Len Fanelli

I think the stronger springs are standard on the TF 1500. As the XPAG likes to eat cam followers, stronger springs just exacerbate the problem. (The original upper & lower locators can be reused with the roller cam, with just a simple modification to both, so they're well worth getting. I used my originals & local springs on my roller cam installation). I believe the only way to test the effectiveness of a valve spring is by using a spring tester such as a Rimac. Cheers
Peter TD 5801
P Hehir

Peter, I don't understand your answer to Laurent's question. How does your response answer Laurent's question about what type of springs that he has? Bud
Bud Krueger

Bud I have no idea what the standard spring length is but I suspect that the standard & 1500 springs may well be a very similar length. I should have said that measuring the spring length isn't the most reliable way of determining "What type of spring it is". It's possible that well used 1500 springs may even be identical in length to fairly new 1250 springs. The 1500 had the stronger springs & they were often fitted by owners of the 1250 to increase RPM before valve bounce. A Rimac is the only way that I know of to correctly identify a valve spring. Once tested Laurent should then be able to find the answer to his question by comparing the published 1250 & 1500 spring pressures. Hope this clarifies things. Cheers
Peter TD 5801
P Hehir

Okay. So, I guess the answer is that we can't say what they are by the length measurements alone. But, Len has a matching set that he's willing to give away. Is a Rimac a very common instrument? Don't recall having seen one. Bud
Bud Krueger

Bud here's a Rimac valve spring tester in use. This was used to check the springs from Performance Springs in Brisbane that I installed with the roller cam. The scale on the right measures the compressed length of the spring & the dial reads the spring pressure at that length. Cheers
Peter TD 5801

P Hehir

To test springs without a valve spring tester I use a drill press and a bathroom scale. Must put ply wood under spring to spread load and wife doesn't know I used her scale. PS set stop on drill press to get same travel on all springs.
Forrest Rubenstein

May be able to identify spring by measuring wire diameter of springs. TDC/26679
Forrest Rubenstein

Thganks for your answers.
The wire diameters is easy to measure :
2.7 mm for the inner spring and 3.78 for the outer one.

I tried a measurement with a bathroom scale but it is digital and really dislikes the progressive strength of the hydraulic press. But it seems that the inner one was the TF ones : strong.

Laurent.

LC Laurent31

Forgot about digital bathroom scales. You need a old spring type scale. Can maybe find one at a yard sale or second hand store for cheep. Drill press works good because they have a stop you can set. The amount you compress the springs will then be same for all the springs. Stronger springs that are the same length will have larger dia. wire then standard springs. Maybe some one that has both types on hand can measure wire dia.for us all. TDC/22679
Forrest Rubenstein

I'm also doubtfull about the strong springs from the TF.
The data super tuning book of WKF wood gives the valve crash speeds for both spring types
6000 RPM for the TD springs and 6500 RPM for the TF

But safe speed is 5700 RPM for both.
Apart for race engines nobody rev at 6000 RPM. No matter reving upto 6500 RPM with the stronger springs.

Laurent.

LC Laurent31

I found an answer.
In the book "Tuning and maintenance of MGs" from P. Smith.
It states that free length of springs for TD and TF are the same :
Inner : 65.15 mm
Outer ; 74.35 mm

So free length does not allow to identify spring type.

And mines are longer... Maybe an after market part.

Laurent.
LC Laurent31

This thread was discussed between 11/12/2015 and 17/12/2015

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