Welding a cylinder block

Welding to cast iron is a bugger. Welding something small like a nut to something large like a cylinder- block will be a *real* bugger due to the vastly different thermal-inertias of the two parts.

Unless you go through some really-complex processes any weld you achieve will be full of stress and will be weak/likely to crack under load.

If you must do it, use blowlamps/oxy-acetylene torches to pre-heat the area of the block to be welded as much as possible - you need to get it as close to red heat as you can! - before welding; then after the welding is complete, reheat the welded area with the torches and then cover it with a heat-resistant sheet so it cools GRADUALLY and the stresses will be reduced, but not eliminated.

Expect the weld to crack! Also the effects of the heating could possibly cause distortion of the block, so check for dimensional accuracy on any machined faces afterwards.

Personally I'd look for some other way to do what you are trying to do.

Could the thing be attached somewhere else like the inner wing or firewall? Could you glue the nut? Could you drill and tap a hole in a suitable place in the block? Ie somewhere where you know there is thick metal and you are sure you won't drill into oil or water galleries. If you do this make sure you use a stud/bolt that expands less than the cast iron.

It won't work, the block is made of grey cast iron the nut is made of eel -- the metalurgies won't mix, grey cast iron can be welded to grey cast iron but involves heating the whole block up to to a high temperture and gas welding the boss on - even then you could find the the whole lot cracks or distorts as it cools.

You might be able to braze (more correctly bronze weld) a boss on but because of the nature geometry of the brazed joint it is likely to be weak.

If you tell us more about what you are trying to do perhaps we can give you a possible solution.

Can be done with a risk of cracking the block. But usually successful.

Electric arc - there are rods to weld cast iron they have a high nickel content instructions are on the packet or ask at a BOC place.

Most likely if you used steel wire in the mig the cooling pull would crack the block at the heat affected zone in the cast iron.

Piece of cake. But keep the attached boss small (a nut is about right) and braze it, rather than welding it. Design yourbracket (or whatever) so that it's not too fussy about exact boss position.

Grind the iron flat first, because there's often a skin on the outside of a casting and it's hard work to braze to that.

-- Smert' spamionam

Well thanks folks - I have got replies ranging from 'it won't work' to 'piece of cake'! I am actually modifying my A-series block for an A-plus distributor (you may remember an earlier thread about this). The retainer is different and there's a threaded hole in the A-plus block, but I don't think the block I have is thick enough to take the hole. I suddenly had this idea of attaching a nut. I don't have gas welding gear but might be able to borrow it. I have done a lot of brazing so could manage that. I even considered glueing a nut to the block but quickly dismissed the idea as I don't know an adhesive that's good in tension and can cope with vibration. Anyway, thanks again for the helpful replies which are food for thought. I suspected there would be problems.

Instead of altering the block modify the distributer clamp

"ops" to do anyway as well as altering the material structure of the block.

Actually the treaded hole I need is only for a clamping screw. The clamp itself does the locating. I will have another look as the dizzy but I don't think it can be modified. There is an item in the Vizard book which says you can use an A-plus dizzy in an A-series block, but you have to use the forked clamp. Unfortunately there is no more detail than that. Very oddly, you can get an adapter for the other way round, ie early dizzy in A-plus block - not sure why I would want to do that. To save me going back to the scrapyard for a butcher's, does anyone have a decent photo of that side of an A-plus block, so I can see what I'm aiming at? I want to use the A-plus dizzy because (a) better design, and (b) it's what I have. My older ones are all knackered.

Why not fit a decent aftermarket electronic ignition like Luminition to the original distributor?

Good idea, but I have 3 or 4 early distributors and they are all knackered, with worn bearings. Most of them are by this time. Also I am mean and this looked like a cheap solution!