[urq] WX head build recommendations

[Graham Allan]

> If I may...
>
> What kind of pressure test are we talking about?

The WX head cracks between the valves, causing leakage between the
combustion chamber and coolant passages.

I also started out intending to do a WX rebuild. Even got an entire
running "known good" WX engine at one point (my original engine has bottom
end damage, as well as the usual cracked head). Waste of time, the head
on that also failed a pressure test. Now going with the flow and doing
an MC transplant.

Having said that - MC heads also appear quite prone to the same cracking
(I had 3 of those heads fail pressure tests as well!). But at least there
are a lot more of them around...

Graham