Cylinder head

[Stubmiester]

I have recently taken on an unfinished restoration "Pick Up"
This week was getting the engine going. Having checked and adjusted spark plugs and dressed and set the points, the engine fired and started-great! or not so great-a real clatter coming from the rocker cover.
Investigated and found valve one permanently stuck open. No amount of taping would free it.
Have removed head and tapped out valve one-it is not bent, a bit carbonised.
I propose to remove all valves-emery down the stems (especially nos 1), grind-paste and re-seat the valves and re-assemble.

Has anyone come across this problem and if so what was the cause?

Separately there are three holes in the head which were blocked off-the contents of which crumbled away. The corresponding holes on the block are still intact. Should the holes in the head be filled?[frame][/frame]

[bmcecosse]

DO NOT 'emery down' the valve stems - perhaps polish with Brasso - but nothing more abrasive than that. Yes - clear out any holes blocked with crud.

[Stubmiester]

Many thanks for the reply, very much appreciated.

The result of the investigation showed that the valve guide appears to have shrunk in diameter??? The nos one valve would fit in the other valve guides and testing one of the remaining valves in the number one valve guide-it would not fit.

The only solution I can think of is to replace the valve.

Out of interest why would you not emery the valve or indeed turn on a lathe and emery? Is it because the stem has to be supper smooth?

[don58van]

Hi S

That is an interesting problem.

I wonder if the problem valve guide was replaced at some time. I know that at least one Mini parts supplier sells undersized guides so that buyers can enlarge them to suit their valve stems. This could be one of those that was clearly not enlarged sufficiently.

Roy and others: what do you think about reaming the valve guide in situ, or replacing it with new?

Don

[panky]

It could be that the valve guide has developed a hard coating maybe burned on oil due to over heating, the blocked waterways could be a clue.

[bmcecosse]

The valves are a defined and accurate size -hence DO NOT emery the shaft... The guide has probably been burred over at the top end when fitting it - gently ream it - a new drill bit hand held will do the job well enough.

[Stubmiester]

Many thanks all for your contributions.

I have elected to turn the valve on a lathe and filed just enough so that the valve moves smoothly in the guide. I then smoothed down with emery, ground in all eight valves and then fitted springs etc.

As for the blocked holes in the head and block-there seems to be no evidence to say that some holes in the block and corresponding head should be blocked so I am removing offending debris and crud-which is soft & crumbly.


Stuart[frame][/frame]

[Stubmiester]

....and here is the completed head....[frame][/frame]

[bmcecosse]

Oh dear - the guide was the problem - not the valve. As you proved by showing it fitted in the other guides!.

[les]

Yes, if I'm reading the post correctly your experiment proved to you that the guide was at fault, not the valve.---two wrongs don't make a right, as they say!

[bmcecosse]

Ah well - we can only lead the horse to the trough.... Now you need a new valve..... And hopefully you are taking the chance to fit new 'top hat' oil seals to the inlets.

[Stubmiester]

Thank you all for your input. Pleased to say, cylinder head painted and installed. Engine running very smoothly.
Next job-Ignition light on!

[firehor5e]

New valve guide aprox £3.00..easy to fit with a copper drift,if you do damage it you can ream it with a suitable drill...easy.. You may have caused yourself some trouble ahead im afraid.

[Stubmiester]

Hello all contributors

In re-reading your replies-I find myself no wiser. So could the contributors please give some clarity to the problem presented in order to help my learning and understanding, I summarise the questions as follows;

1. Has anyone come across the problem of the valve guide becoming smaller and if so what was the cause?
2. Should all holes be clear in both head and block?
3. Why might I have caused a problem in the future because I shaved a few thousands of an inch off the shaft of the inlet valve? (in doing this the valve then fitted snugly into the valve guide Nos 1)

Following several adjustments to the valve clearance I now have a smooth running engine.

Once again thank you to all who commented-it is very much appreciated when people take the time.

Stuart

[bmcecosse]

I suggested the guide may have become burred over at the top. Reducing the valve stem was crazy - you had already proved it was fine by checking it fitted other guides. You now have a worn valve.... I'm amazed you could turn the valve shaft in a lathe. I think you were also told to clear all the blocked holes.....

[Stubmiester]

Thanks bmcecosse

Ok-yes I might be a bit nuts in reducing the valve stem-the best i could do was polish afterwards. I do see your point now however in my mind as long as the stem was smooth and the valve had been re seated (ground in) I felt comfortable in rebuilding the head.
Turning the shaft in the lathe was relatively straight forward. The chuck can accommodate the valve either way and I was therefore able to take off an even amount along the length of the stem.

[bmcecosse]

Surprising - usually very hard material.....

[les]

These are the answers to your questions Stuart, as I see it-----------------
Question 1 ---the problem occurs if the guide is knocked in without a proper drift, because the guide can be burred over at
the point of impact(reducing the diameter at that point) as it appears in your case.
Question 2---all the holes blocked with sediment should be cleaned out, to assist better cooling.
Question3---you might have future problems because below the reduced diameter of the guide, it will no doubt be the correct diameter so when the small reduced size (at the top) eventually gets worn down by the valve movement, the valve will be running in a normal size guide and the valve, now with a reduced diameter, will be too slack.

[Stubmiester]

OK-Understood and my thanks Les.

[les]

------however if its running ok, hopefully you will have plenty of happy motoring!