Cylinder Head Questions

[Kevin-G]

Hi, I am currently rebuilding my Morris 1098 engine which if genuine should be dating from around 1970.

I have a few questions which I hope someone will be able to answer for me.

The head that came off the engine seems odd. In the photos you will see that the collets holding the top of the valve do not seem to sit right. In fact a part of one has broken off. Is this normal?

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The valve oil seals are the older O ring rather that the top hat ones and so I am suspecting that an earlier cylinder head has been fitted, but with later collets. Is this correct.

On another note the head seems to have had some porting work done to it.

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The inlet valve ports seem to be very big compared to another cylinder head that I have got, in addition they don't seem to be quite round which is what I would have expected from a machined part.

my other cylinder head, which I believe may be from an A+ engine, has a port diameter of about 29.5 mm

My other head looks like this:

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This may be from a 998 engine, but is it worth fitting, for the newer oil seals if nothing else.

Does anyone know if this has the hardened valve seats for unleaded fuel?

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Many thanks

Kevin

[Kevin-G]

ahh, just googling during my lunch break.

It seems that my original head the valves are missing the little collet clips. People have said that they are worthless anyway so can I just not bother replacing them?

Would a factory engine have come like this?

[liammonty]

You're correct regarding the collets - they are standard. No spring clips is also quite common - I have never experienced trouble with them missing. O rings were standard too - top hat seals were never fitted to Minor engines, only later iterations of the A Series.

I've just checked against and old 12G202 head I have, and your inlet ports appear standard size, at around 31mm. Finally, it looks to me as though the valve seats have been replaced to my untrained eye, but whether the exhaust seats are hardened is anybody's guess!

I believe you'll experience a performance drop if you fit the 998 Mini head, as valve sizes are slightly smaller. The 1098 12G202 head was actually the first 'Cooper' head, used on the 997 Cooper, before the improved 12G295 head (and another the number of which I forget) were brought out for the small-bore engines. So, I would stick with the original head.

[philthehill]

I cannot see any broken off parts in the photos posted!
The 12G202/1098cc head would be fitted at the factory with the spring clips (Pt No: 2A12).
The spring clips were fitted because at high revs the collets tended to pop out due to valve spring float.
BMC later improved the fit/interface of the collets into the valve spring caps so in later engines the spring clips were therefore no longer needed and the later collets had no provision for spring clips tp be fitted.
Very much in the same vein as was the shroud (Pt No: 2A544) discontinued with.
The engine can be safely run at normal revs without the spring clips but if using high revs the later collets and spring caps should be used, making sure of course that the valves are suitable for the later collets/caps.
The 'Top Hat' seals should be only used with the appropriate valve guide which has a groove at its upper end to retain the seal in its correct position.
Some fit the Top Hat seal to valve guides without the groove but personally I would only fit to the appropriate valve guide.
The consensus is to fit the Top Hat seals only to the inlet valve guides so as to reduce the amount of oil being sucked down the inlet guide. The exhaust valve guides need a small amount of oil to help lubricate the valve stems therefore the Top Hat seals can be left off.
The other head with the yellow paint appears to be from a 998cc 'A' Plus engine.

[RobThomas]

One of the collets on the inlet for number 3 looks like it has broken the top off.

It would be handy (for me, anyway) to have a picture of the acceptable combinations of collet shape and cap shape and which engines they came from. The long and single groove collets have, I think, a 10 degree internal angle against 14 degrees for the 1275-esque 3-groove collets. Not always easy to know what cap angle I have and there are several different designs.

Anyone up to the task? I'd really like something to print off and stick to the plastic tube with all my spare valve bits.

[philthehill]

Rob
Some information regarding collets and valve spring caps contained within the parts list links below for starters:-

http://www.somerfordmini.co.uk/eshop/in ... age&id=115

http://www.somerfordmini.co.uk/eshop/in ... age&id=116

http://www.somerfordmini.co.uk/eshop/in ... age&id=117

http://www.somerfordmini.co.uk/eshop/in ... age&id=118

[RobThomas]

Thanks for that info Phil. It was more a case of getting a quick photo-I.D. thing on a piece of paper. Some caps have a ring groove in the top, some are flat and some have a countersink. Not sure if there are any others out there and the risk of damage due to a dropped valve....yikes. Not an urgent job but it would be handy to have a definitive guide.

[philthehill]

Rob
As valves, cotters and valve spring caps only fit in sets i.e. the cotter should fit the valve stem and the valve spring cap.
Whilst nice to have I see little point in having a list of valves to cotters to valve spring caps as they are on the face of it not interchangeable.
If there is any doubt as to the type of valve/cotter/valve spring cap fitted the supplier should be consulted.
Phil