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Pre Unit Valve Spring height / pressure #792070 12/04/19 11:27 pm
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Samsmc1 Offline OP
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Can anyone tell me where to look for the spring pressure and spring height for a mid '50's T110 / TR6?
I'm also curious to see if anyone has ever had any problems with the springs available from either MCA or Wassell's in the UK? Their springs are supposedly made in the UK.
Thanks
Sam

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Re: Pre Unit Valve Spring height / pressure [Re: Samsmc1] #792098 12/05/19 8:01 am
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Stein Roger Online Content
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On the first question I don't have an answer to fitted spring height, but will offer some good information on spring pressures, lifted from this forum earlier.
I only concern myself with coil bind, which usually doesn't become a problem unless you use a high lift cam or incorrect valves, springs or spring cups.
Seated valve pressure is however very easy to determine. Please read the passage below, written by the incomparable Pete R some time back.
I use this method myself now and don't mess around with fitted spring heights anymore. I measure the springs free length beforehand to determine if they're close to spec.
If seated pressure is low (too high hasn't happened yet) I use spacers or shims under the spring base cup.
I will add that on a normal engine that isn't modified in any way and the springs are in spec, I won't bother checking spring pressure.
NB! It's important to know that Triumph changed the spring cups for thinner ones to go with longer springs in the late 60's. These parts must not be mixed, for obvious reasons.

Correct valve-spring seated load is probably hand-written into your manual, but you won't find it in a Triumph manual.
You'll find incorrect figures, 87 lbs (40kp) EXHAUST and 75lbs (34Kp) INTAKE, which were never used in production.
This would bring a new exhaust spring close to coil-bind (about 0.060" from coil-bind with standard cams).
The outer valve spring free length in the manual is also wrong.
I measure them at 1-5/8"(+1/32",-0.0),not 1-1/2". (40,6-42mm)

Try for seated loads of 75lbs (34Kp) EXHAUST, 65lbs (29Kp) INTAKE.
Measure it with bathroom scales. That's a little more than Triumph used, but not much.
We can assume these pushrods were correctly seated on the cam-followers and rocker-balls when they were installed.
Usually if pushrod cups are chewed up at the outer edge,they've been binding on the rocker arm above the rocker-ball.
*The cup in the pushrod should be just under 5/32" deep.You can grind some off the end to reduce this depth and increase clearance if there are geometry problems.
*Usually there's plenty of clearance in this area on a 650 Triumph.You can swing the pushrod more than 15 degrees from square on the rocker-ball.You need less than 10 degrees.


To use bathroom scales, find a stick (a 2 by 2, a broom handle, whatever) and put it on the scale. Push a valve top against the stick until it opens and read the scales.
Takes some getting used to, but you soon get the hang of it.

Thanks Pete
SR

Re: Pre Unit Valve Spring height / pressure [Re: Samsmc1] #792108 12/05/19 4:15 pm
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Samsmc1 Offline OP
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Pete
I know how to check the spring pressure, but without knowing the length of the installed valve, I have nothing to go by.
There are numbers in the unit workshop manuals, but not the pre unit, plus pre units used different springs and valves if memory serves me correctly.
I may call Kibblewhite and see if they have any numbers I can use - I guess it's worth a try.

Re: Pre Unit Valve Spring height / pressure [Re: Samsmc1] #792138 12/05/19 11:25 pm
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Stein Roger Online Content
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Just trying to help, nothing in your post pointed to your proficiency. John Healy and others have those numbers, but I save stuff like that:

John Healy, Valve stem lengths:

The distance from the head to the tip of the stem when valve seated on the alloy head is on 650 models:
Intake 1.743"
Exhaust 1.681"

Hth
Stein Roger


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