Seized exhaust manifold nut

[Lily the Pink]

Having released 7 of the exhaust manifold/header nuts (Porsche 944), I am left with just one which won't budge. It is tucked in fairly tight to one of the pipes; too tight to get a ring spanner or socket on, and an open ended spanner only results in rounding off the nut's corners. I have sprayed it liberally with WD40 over the last few days. I think my next option is to grind down the edges of a 13mm ring spanner until it is thin enough to fit - but of course that will weaken the spanner. If that doesn't work then I shall have to work out how to get a flame down there to heat it up. But before I do any of that - does anyone have any experience of Wurth Rost Off Ice (or their Blue Ice, or any alternative products) ?

Or any other ideas ?

[Lily the Pink]

Thanks all, got the problem nut loose with a good dose of penetrating oil and a ground-down ring spanner; needed to reduce both its thickness and its overall (outside) diameter in order to get it on the nut - see the narrow gap between nut and exhaust ...



Getting all back together will be fun; no chance of getting a torque wrench on it.