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MG Midget and Sprite Technical - Single or double valve springs

Hi
My brother and myself are finishing off a project 1500 midget that my dad had been doing for years.
We have sorted out the engine parts he had done over several years it has had a full bottom rebuild and balanced. The head has been modified to stage 2!!! And is fully built and never used.

We need some advise on the valve springs at present they are double one red one yellow but we have found a complete piper 270 cam kit with piper single springs all boxed and new. Do we use these springs or keeps the double ones on the head. We will be using the piper 270 cam when we rebuild complete engine.

Any help and advise would be gratefully received and of course stop the arguments.
S Rix

If Piper supply the cam kit with springs, use them. That's what I would do.
Dave O'Neill 2

X2 I'd also use the matched springs for the head build that came with the kit, unless your father left notes lying around to say and prove other wise

P
1 Paper

To me it sounds odd.

1. I have used standard double springs on my car with Piper 270 cam with no issues.

2. I can't see how you would get sufficient spring rate in a single spring to match the standard double springs.

3. The Piper website shows a picture of a kit with both large and small springs in.

Are you sure they aren't just replacement outer springs? Use those plus reuse the inner springs.

Cheers,
Malc.
Malcolm Le Chevalier

"we have found a complete piper 270 cam kit"


You could base a nice philosophical discussion of that. Not knowing what you don't know? Do you suppose that what you cannot see, doesn't exist? Maybe the complete kit isn't as complete as you think it is. Another (smaller) box of springs lurks somewhere in the garage - or if not in the garage then somewhere else in the universe perhaps. Have you checked all dimensions?

Its a discussion I have with myself on an almost daily basis when looking for things in my garage.
GuyW

Hi
Thank you for your replys. For info the kit was a sealed package from piper with camshaft, lifters and springs kit number KBTR270 for a triumph 1500 the springs are VSSTR4 which I Have just checked and piper web site says these are single springs. We will do some more reading tonight and maybe toss a coin. Thanks
S Rix

Guy

I found 3 unmatched socks in my dryer last weekend .... are they yours?

Damn worms eating holes in everything these days

Prop
1 Paper

Malcolm, I seem to recall that double springs don't increase the rate, rather they guard against spring bounce due to resonance at high rpm (?)

S. Rix, When swapping springs, as well as rate there is fitted length and risk of coil binding when compressed to check.

I would use the ones in the sealed kit, but check the measurements and turn the engine over carefully by hand during assembly to check all is well.
AdrianR

I'd guess that Piper know a thing or two about cams and springs !!!

If you look at Vizard - O.K its written for the A series but most logic is transferable - he warns against overspringing as it 'generates increased frictional losses and as a result more hp is used just turning over the engine'

Also this is a 1500 and its not renown for its high reving qualties, so revs should be well within the bounds of modern high spec single springs.

I would phone / e mail Piper if in any doubt and ask them as they made the kit - just check the caps etc for satisfactory location of the springs.
richard b

This thread was discussed between 09/01/2018 and 10/01/2018

MG Midget and Sprite Technical index

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