How can I Weld Kb Manifold

trying to weld an old Mag KB manifold - seems to crack as soon as it cools and the weld is chalky - grabbed an old mag blower case and welded it fine.

Any ideas?

 

The only thing I can suggest is trying to let it cool slower, do a good pre heat and after welding wrap it up or use a torch to try and hold some heat in it. Is there any stress on the area that you are welding? That could be causing a crack also.

COREY

 

You need to drill a small hole clear through the casting at each end of the crack, making sure that the crack don't go past the hole otherwise you keep the chasing the crack clear across the casting.

Dale

 

V cut the crack clear out/through, butter the side walls and eventually bring them together with a final pass. Some peening won't hurt either. Weld a bit, peen a bit..and so on.
Trying to gloss/cosmetic weld over a casting crack will never succeed.

 

I weld mag all the time first take a heat lamp and warm it up for a few hours then get after it with your tig machine after your done you need to burry it in lime or you can use floor sweep...yes floor sweep in 30 min. take it out and go racing..Dave Lowe

 

Combine all of the above and you got it covered.

 

As a certified welder the previous answers are all correct,but one thing that I learned over the years is call the manifold mfg,and get the metalurgy on the unit.From here take that information to your welding supply,and he can probably set you up with filler rods,gasses,welding procedure.After you have this info you should be good to gne more trick for you is pre-heat parts{heads,manifolds,etc} use your propane grill to pre heat parts,and a thermal stick.It heats the part more even than a rose bud.Hope this helps,DAVE

 

Is this a weld weave technique?

 

good call on the gas grill..never thought of that.D

 

Buttering or wetting the walls means to get a bead bonded to the clean parent metal. You do both walls and build up/work your way back to the middle and final join the 2 halves of the crack.
Sometimes, depending, I will wet bead the walls first with no filler to get all the junk pulled out. Then recut it a touch to have clean metal.

IF you try to join and weld both together at once it will crack again.
IF you don't cut out the crack completely it will crack again. The crack is still down there on the bottom side and it will do again what comes naturally.

 

Is the "wetting" part of this conversation specific to magnesium or cast aluminum also?

 

Sodak, works on everything cast.

Dave Koehler
http://www.koehlerinjection.com