Thread: Alloy Cylinder head repair

Originally Posted by RVK 355

Guy at work is currently fixing up the head gasket on his 5 cylinder (yes 5 cylinder) volvo, not to sure what year or model, bit of corrision on the alloy head which he wants me to weld up for him.

Now i can some what remember reading a thread once on another forum (cant remember where or when) but i can re call that once the cylinder head had been re welded, the guy peened the welded area with a hammer to work harden the area again from goin soft from welding.

Does this sound rite? also filler wire, i presume 4043 would be the way to go.

anyone got any other pointers or advice

Cheers
Mondo

We have always used 5356 filler with good results, (haven't had a comeback that I am aware of).
I assume that you will be tigging this - don't even contemplate mig.
You will want to preheat the whole head at least to some degree to combat thermal shock plus it will make your job easier to weld, then cool slowly out of draughts etc.
Is the corrosion in an area that will be machined or simply filed flat?
You will want to ensure clean parent metal so don't be afraid to rip out damaged metal to expose good clean ally. It is far easier to add metal to a clean area than to battle to get fusion around scale/ oxides. Make sure that you overfill and machine/file back rather than underfilling and being left with a crater.
The peening is not so much to harden the metal as to stretch it removing any stresses built up that could cause cracking.
There are many variables when welding castings and forgings such as transition from thick to thin areas and component restraint. A heavily restrained component will need even heating and cooling where a component that can freely move can handle a more localised head input. The same applies to areas where their are ribs or such that are prone to cracking.
Perhaps post a photo so we can see exactly what the issues may be?
Hope this helps.

as the robber says,remove ALL corrosion and make sure its back to pure alloy.
preheat gently and thouroughly allow heat to soak and preheat again.i have mig welded 6 cyl falcon heads but i recomend highly that you dont unless you are very familiar with your machine and process.weld up and build higher than needed by 3 to 4mm and check the lay of your fillet/puddle for small craters etc.All alloy heads i have worked on need and should be decked before refitting and it very normal to take up to 15/20 thou off of gasket face to true up head.leave excess weld for the mill cutter to take off.i have done heads with valves left in also.cheers

Cheers for the replys guys.

it ended up being abit of a rush job the other nite so i didnt have time to reply

I didnt use any pre head, just went straight in and welded it up, corrision was ground all out back to bare metal but there was still some contaimnation present when i welded it.

i will try get some pics up.

Cheers

I think peening is more of a way to prevent contraction cracking in cast iron, i could be wrong though.

Originally Posted by Graziano

I think peening is more of a way to prevent contraction cracking in cast iron, i could be wrong though.

Peening can be used on all metals. Cast iron is one of the more common ones where it is used but it is often used on ally castings which can be prone to cracking upon contraction. All it does is stretch the metal as it cools, hopefully relieving any stresses built up in the joint.