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MG TD TF 1500 - Valve stem seal and cotter

Good day to all,
I have a question about the original style valve stem seal. As evidenced by the attached pictures, my machine shop installed my stem seals incorrectly. I first thought I would send the head back, and then just decided that I needed the experience doing it myself. I have removed one valve spring and it looks to me like the cotter pushes down on the seal enough where it might force it down onto the valve stem proper. See the "bend" where it appears to push it down on the left side? This is starting to force it down onto the stem. Is this correct?

Cotter thickness:0.267"
width of valve stem indent including radius:0.343"
Thickness of seal:0.114"

These measurements force the seal down over the radius by 0.038". Does this sound right?

See attached photos

Thanks for any help you can give,
Jim TD177434





JV Smith TD17744

Image of valve stem

JV Smith TD17744

Hi Jim,
see WS manual Fig A 21 the seal is below the cotter but just above the cup; it's mainly a seal to retain oil on the top of the stem for tappet action. It also prevents the oil to go donwward the stem. Then, the shield completes the oil deflection.

Laurent.
LC Laurent31

Hi Laurent,
Yes, in the WSM it actually looks like the cup retains the seal, or keeps it from moving down the shaft, but neither my old cups nor my new ones prevent the seal from moving down the shaft at all. So, the seal is only retained in the groove below the cotter.

However, my cotter wants to push the seal down past the lower radius of the groove slightly. I just don't know if this is correct, or if I have a problem with some of the parts.
JV Smith TD17744

Jim
Lost count of how many times I've seen the seals fitted incorrectly like in your 1st pic. and by some very pro. engine builders to boot -Fitted like that they do nothing---The mistake they make is fitting the 'O' ring on the stem first before fitting the spring setup and pushing the o ring down the stem like that-

Your other two pics are correct-

The correct method is to fit the springs and cap, compress the assembly down, then fit the 'o' ring to the stem and push the keepers down against the 'o' ring (there will be some loading against the 'o' ring) Then let the spring assembly back up and the cap will trap the 'o' ring up against the keepers and the taper inside the cap will wedge it all in place
You can have a little try without the springs--just to see how it works, just sit the cap down over the valve stem, fit your o ring and keepers as in pic2 and pull the cap up against them, it'll feel like the o ring is too fat but spring pressure squooshes that up when finally assembling
The whole idea of it is to prevent oil that gathers on top of the cap from running down the stem--it works quite well when fitted up correctly and no other whiz bang seal is needed.
I've run a few without the tin spray shields fitted as in your 1st pic. and just the o rings and they've been quite good without the shields without any oil usage issues at all-

willy
William Revit

A little tip fitting the rings.
Cut the end off a mastic nozzle so the fat end is the same diameter as the valve stem. Ease the O ring over the stem using a small ring spanner. No broken fingernails or damaged O rings.
Ray TF 2884
Ray Lee

Willy has it dead right.
Mount the springs (right way round) then Oil shield, then cap and compress. Thats the point when you mount the O ring
It seals against the cap and collets.
If the fitter mounts the oil deflector first. It will direct oil strait down the valve stem regardless of the O Ring -like a reservoir. It Has to be on top to act like an umbrella.
It works very well.





Rod Jones

Thanks for all of the help.

For those looking at this thread in the future, here are my observations.
When I just placed my O-ring in the cap, it just fell right through. So, I thought maybe the I.D. of my caps was wrong. However, when installed on the valve shaft, it expands enough that the cap keeps it from moving too far down the shaft.
Ray's method of using a caulk nozzle to feed the O-ring down onto the valve stem works like a charm. Doing it with my fingers with the spring compressor on was virtually impossible.
Lastly, pay attention to Willy's sequence of installation. It is the only one that works, in my opinion. If you try to put the O-rings on before the cap, the cap will just push the O-ring down the shaft. I suspect this is the method my machine shop used.

Thanks again for the kind advice.
Jim TD17744
JV Smith TD17744

This thread is a great example to those of us who are "keen amateurs" - ours is not a hobby for the gung-ho or the for faint hearted, but if we're willing to learn, there is so much help available if we ask nicely. Good to see.
John.
J P Hall

Jim
I meant to comment on your shiny valve springs, they look like a set of aftermarket competition molly springs from here---?
Would you know the spring rate and fitted seat pressure of those, they look quite strong for a T type -just interested in what you're up to-
willy
William Revit

Willy That would be one of my Abingdon Perormance Ltd. Roller camshaft kits, Stock replacement, Street Performance NA/ SC. and Race cams.
Roller cams require a much stronger spring to follow the rapid acceleration/ decelerration of the lobe.
Since all of my cams are a relativly mild grind the use of the the lightest roller cam spring is needed.
My springs are 165# closed & 340# open pressure.
(Super Clean wire, shot peened and heat set double springs)
Roller cam kits
CSI Distributors
Roller rocker arms
Teflon valve stem seals
and more
In stock
Safety Faster!
Len


Len Fanelli

Thanks Len,
Your reply keeps me from possibly giving Willy incomplete information.

Jim
JV Smith TD17744

All good Jim -Thanks
William Revit

This thread was discussed between 05/06/2022 and 13/06/2022

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