Cylinder head update - purchased a replacement

[eng622]

Purchased a head supposed to be from a running engine. So far found one stud on the thermostat housing bent and with luck managed to replace with one from the cracked head.
Now the differences. The cracked (I.Searle) head has exhaust valve seats inserted and the new one they are call done. Assume the IS one is unleaded but not sure about the new one. All the valves are non magnetic so assume stainless assume no way to tell if unleaded.
Took out an exhaust valve from each head. The cracked one has long collects on all plus intake but the new one has a mix, long except no1 on exhaust and short on intake. So the new one has different valves so intending the use the IS ones as all the same and only 10k miles.
Now the springs, the new ones (at least the exhaust) are longer at 1 3/4 ins the cracked being 1 1/2 ins, so what should I use.
Next issue is valve guide seals the new one has push on O rings and the cracked one appears to have O rings pressed into the guides. In the head service kit there are O rings but so small in diameter how do you get them on.
Finally looked at 2 exhaust valve seats and they need work as small pits. Have a valve lapping suction tool but finding it difficult to stick on the valve, any ideas on alternatives, do not want to have reground if avoidable.

[philthehill]

Some engine re-conditioners fit 8 unleaded valve seats and some fit only 4 on the exhaust valves. Both are right.
Fit a new set of valve springs but if you must use the existing valve springs use the 1.75" springs as that is the specified free length of a new valve spring.
Fit the valve guides with the groove for the top hat seal to the inlet valves. Fit top hat seals to the grooved inlet guides. Discard the 'O' ring seals on the exhaust valves. There is no need for seals on the exhaust valves/guides.
Get the valve seats ground after you have fitted the new valve guides.

[eng622]

The new head has 1 15/16 ins inlet valves which I understand is correct including exhaust(mine 1.75 ins). All the springs in the new head are longer than the I Searle ones so won't be using those.
I read the long collet valves are the early ones replaced by short collet. Intake valves on the new head are all short and looked better than the IS long collet ones. The valves/seats lapped up with no problem.
The intake oil seals are top hat. Some are loose, they just push on, no groove in the valve guides. Should I replace with standard O rings. They are in the kit from ESM. Problem is how to fit, ESM say they are correct and a tight fit is necessary. How on earth can you get an O ring with a 3 mm ID onto the valve stem and past the collet groove.
Some of my tools do not work on the MM. The spring compressor slips off too easily and the valve lapping tool (the small end) for the exhaust valves will not stick easily as diameter too big.

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[philthehill]

If your head is as I believe a 12G202 casting then the valve sizes for a standard head are 1 5/32" inlet and 1 " exhaust.
If they are not these sizes the head has been modified and is not standard.
There must be a groove in the valve guide to retain the top hat seal. The correct guides are available from ESM.
Forget about the 'O' rings as they are next to useless.
Saying that - those small diameter 'O' rings do fit over the valve stem and they are supposed to fit in the bottom of the collet groove and do not fit over the valve stem below the collet groove.
The valve stem/collet groove has to be correct to accept the 'O' ring seals. I would suggest that your valves are not suitable.
So long as you have the right collets and spring caps for the valve stem it does not matter that they may be different.
The valve springs should have a free length of 1.75". Any less and you will not get the right loading on the valve, valve collets and valve bounce may occur or worse.
The use of the correct valve spring compressor is important. I use a Sykes Pickavant 039900 compressor for all 'A' Series heads.
https://www.ebay.co.uk/itm/355070913813 ... R673xP6fYw

[eng622]

The cracked head looks to have new valve guides, they are grooved with top hats fitted. Are they easy to get out as can put these in the new head.
Regarding the small O ring seals assume they will only fit on the long groove valves. Cannot see once in the groove how they work as no where near the guide where the top hats fit.

[philthehill]

The grooved valve guides can easily be knocked or pressed out.
The dimensions of the tool required to remove the guides is stated in the BMC wksp manual as is the fitted height above the valve spring seat.
The valve seat should be cut or ground to the new valve guide. Valve seats are not necessarily concentric to new guides and have to be cut true.
The 'O' ring seals do not work and that is why BMC discarded them for later heads.
Below is a photo of the correct tool I made for removing and fitting valve guides.

Valve guide tool 1.jpg (20.82 KiB) Viewed 46817 times

As my preference is to use a press to remove and fit the guide. I have made a spacer and cap to enable the valve guide to be fitted at the correct height every time. See photo below

Valve guide tool 2.jpg (85.42 KiB) Viewed 46815 times