M20 eccentric max adjustment

[billy]

Just doing the valve adjustment on the 525 m20 engine and im up to maximum adjustment on one valve, looking at the top of the valve its flush with the top of the spring, all other valves have about 5mm protruding to contact with the eccentric on the rocker...any thoughts on why this one is lower? - I cant seem to see any wear on the top of the valve stem, its completely flat, ie no grove from the eccentric

any ideas would be very helpful at this stage

billy

[Ross]

This could be the result of a previous valve job where the stems were ground.
If the stem is not galled or pitted, there is sufficient material for the keepers to stay in place(apparently) and you can make the lash adjustment, then no worry as I see it.

[billy]

The cylinder head has never been touched from new, apart from valve adjustment - i have seen that you can get oversized eccentrics which im guessing would take up the excess gap, im just concerned as to why the stem is flush with the spring top and how long is it going to last should i get an oversized eccentric

[billy]

Heres some pictures ive taken of the problem, the first one is of the problem, the second is what the top should look like

5294

5295

Now that ive taken a closer look at it, i think its fairly certain that the top of the valve has either sheered off or has been ground away over time

From what i can gather it seems i happened to check the valve clearences just in time, it looks like the spring retaining clips are just about top pop off?

so thats a head removal and new valve then is it?

[Barney Paull-Edwards]

Yup! Time for a head job, valve stem tip is stellite tipped and its become detached. Get the usual pump job done at the same time and you`re good to go.Might pay to get the sump flushed in case the bit is still there.

[Paul in NZ]

ouch....i was going to post that the top of that valve didnt look quite right...

[Ross]

And that ain't right.
Best to replace that valve before the keepers fall out, then.....
Is the eccentric worn out as well? Very curious

[billy]

And that ain't right.
Best to replace that valve before the keepers fall out, then.....
Is the eccentric worn out as well? Very curious

the eccentric isnt worn at all, it does just appear that the top of the valve has just sheered off at some point - i wont risk starting the engine again, ill get on with removing the head.

do i need to unbolt the head in a certain sequence to avoid it warping?

[whiskychaser]

do i need to unbolt the head in a certain sequence to avoid it warping?
My connection is playing up so if someone else answered this ignore it. Yes you do need to unbolt in a sequence. First let the engine go cold overnight. Then unbolt diagonally starting from the outside and working in. (ie top left then bottom right, top right then bottom left and working inward) There is a knack to taking out the M50 camshafts without snapping them like a twig. (I've done it.) Think you are OK with your motor but to be on the safe side best ask-seems you have been lucky so far:)