Valve-clearance checking necessity

[hatman]

Thanks for that little lot Martin - you've certainly given me a few options of which, I think, the extractor remedy looks the most likely. Dunno about the nitric acid gig though - where would you get it? how long does it take? what happens to all the dissolved steel/acid mix in the stud hole? are you certain that it doesn't attack ally? who killed Cock Robin etc?

[M100]

Unless you can source some via a university or similar the best bet for Nitric Acid is probably this lot.

http://www.thechemicalshop.com/index.as ... oductid=41

Keep the car out of doors if at all possible. Build up a substantial dam of modelling clay or putty, with a syringe (fitted with a needle) drop a few ml onto the top of the stud, repeat this on a regular basis but only so the top of the stud remains under the acid. You don't want an excess building up. Eventually all you will be left with is a liquid in the hole with no steel and no damage to the aluminium. Leaving it for a few days will do no harm the aluminium won't be attacked at all, just the steel. The residue can be sucked out with a syringe and disposed of in a small container filled with baking soda (sodium bicarbonate) Double bag it and then place in another container in the bin come collection day.

Protective gear is essential and that means face and hands. Doubling up on the eye (full face plus goggles) and hand protection (double layer of gloves) is a good idea. You don't want to be breathing any of the fumes either but if done outdoors and you are upwind and not leaning over its not a problem. A source of running water nearby is also essential. Preferably wear the minimum of outer clothes so they can easily be removed in case of spillage.

A material safety data sheet is here

http://www.physchem.ox.ac.uk/MSDS/NI/nitric_acid.html