The Triumph Dolomite Club - Discussion Forum

paulsprint wrote:Jon, the duration is 280deg and full lift is at 108deg ATDC on the inlets based on 32/68 68/32

hope that helps

Thank you kindly Paul, I have done it now and picked the brains on another site as I was told the correct way is add degrees BTDC to degrees ABDC + 180 divide by 2 and take away the degrees BDTC. AS I stated earlier I am never too old to learn

Dolly racer 33 wrote:I would think many people have done that. I do not suppose in the short term it would cause a problem but in the long term the spring would probably fail prematurely. However as most people on here are rebuilding there engines to get the maximum performance from it, you will lose power because the springs are the wrong way up. It will take more pressure to open the valve with the spring installed upside down thus robbing you of a little power.

If it did not matter there would not be a top & bottom.

Only a small amount I know but added together and spun at 6800 rpm and the extra weight of all those coils would be a lot of weight to throw about.

Its about spring rate isn't it. Stiffer at one end than the other. So when the valve is about to come to the end of the spring and change direction there is an increase in resistance to slow it down. Yes?

Yes, and the valve moves slowly to start with up the camshaft ramp then faster as it comes to its peak, then must have good pressure to close the valve again quickly.

Ken.

Yes!

Dolly racer 33 wrote:Yes, and the valve moves slowly to start with up the camshaft ramp then faster as it comes to its peak, then must have good pressure to close the valve again quickly.

Ken.

Hello, is that so? The spring consistansy is alway's the same. Also with progressive one's. When you have two the same progressive springs, one up and the other upside down. You add the same force on both, they will be depressed the same lenght. They both start to depress on the weakest point and than when more force is on they start to depress the harder point. These progressive springs are to get the valves closed quicker but not to have a resonance or bouncing.

I know this was not good english but it does not affect the spring caracteristics how the spring is mounted. The spring alway's starts to depress on the weakest point first and than go into the harder point.

Jeroen Rothman

Think of it as a stiff spring glued to a soft spring. The soft bit will be made to compress more than the stiff bit as the cam lifts it. This means that at the low part of the cam profile there is little resistance. Somewhere in the compression (usually in the bigger bit of the cam profile) the coils of the soft part will touch, which makes that bit like a solid tube. All the compression then goes into the stiff bit, which then gives a good strong return when the camshaft stops lifting it.

but in theory it should work the same either way up.

I would have thought it'd be to do with one end being heavier than the other, you want the heavy end to stay still as it's going to require more force to get the heavy end to accelerate as fast as the lighter end.

triplecustard wrote:but in theory it should work the same either way up.

Ooh hang on, I thought of a reason why it wouldn't. with the "soft" part at the bottom (i.e. the bit that doesn't move) the spring could flap around if it was compressed?

You need to have the spring the correct way around as your moving more mass
Its only grams BUT IT MAKES A DIFFERNECE TO AN ENGINE DESTINED FOR 7000 RPM
most of its life ( dam cap locks)
It can make the valve move around more wearing the guide prematurly
The valve head wont seat correctly and then it may fall off destroying your engine
Not so crittical on a road engine
Soory for the spelling im drunkl

you mAY BE DRUnk but you explAINED THAT VERy well

These show a valve spring in action
http://www.youtube.com/watch?v=_REQ1PUM0rY
http://www.racingsprings.com/movies/test004.avi
http://videos.streetfire.net/video/Beeh ... 155966.htm
This is also a good site just to have a look around
http://www.engr.colostate.edu/~dga/high_speed_video/

trackerjack wrote:

Dolly racer 33 wrote:I would think many people have done that. I do not suppose in the short term it would cause a problem but in the long term the spring would probably fail prematurely. However as most people on here are rebuilding there engines to get the maximum performance from it, you will lose power because the springs are the wrong way up. It will take more pressure to open the valve with the spring installed upside down thus robbing you of a little power.

If it did not matter there would not be a top & bottom.

Only a small amount I know but added together and spun at 6800 rpm and the extra weight of all those coils would be a lot of weight to throw about.

So I was right about the why I just was not aware of a difference until I read it in the book.
DF the "GURU"

DF wrote:You need to have the spring the correct way around as your moving more mass
Its only grams BUT IT MAKES A DIFFERNECE TO AN ENGINE DESTINED FOR 7000 RPM
most of its life ( dam cap locks)
It can make the valve move around more wearing the guide prematurly
The valve head wont seat correctly and then it may fall off destroying your engine
Not so crittical on a road engine
Soory for the spelling im drunkl

You have convinced me. The spring does work the same way upsidedown but when upside down you move the heavier part down. When mounted ok the lighter end does the moving down and the heavy part of the spring sits on its seat.
I had to be sober first to understand it.

Jeroen Rothman