Z28 exhaust manifold crack opinion

[KevinW]

Thx, I talked to my neighbor and he has used the nickel stuff before. Just need to arrange for a fix try

[KevinW]

OK, my neighbor only has the nickel in stick format. So I went and bought this NI55, only $63 for 2# at local McMaster-Carr. For that price it is worth a try (same stuff $80-$100 on Amazon). I have a bunch of rusted manifolds that I can practice on

I will try the "cold" small puddle method first, then the 100 Deg small bead 2nd, with ping plannish the welds. If neither of those work, then I will try the full heat in BBQ for 400 deg, weld full and slowly let cool for a day. Fun!

[Hotrodpaul]

I would be curious to know how this comes out as I have a cracked manifold on my original 69 Z-28 that I plan to repair. My guess is that some preheating and slow cooling will be required to prevent a brittle high stress weld area and to keep the weld from cracking in the future. Remember the manifolds are subjected to large thermal stress cycles of expansion and contraction in normal driving, probably what cracks most manifolds in the first place.

Paul

[ban617]

I would pre-heat it weld it then put it back in the grill & use the grill to bring the temp down... or make a sand heat sink to weld it in then cover it with sand to cool slowly....

[ban617]

Also I would Tig weld it only because you can control the heat easier ...

[big gear head]

Gas welding with cast iron filler is another option. Indy Cylinder Heads has a special oven that they use to weld cast iron while it's hot.

[KevinW]

I have been thinking about what I have to use. I do not want to bother my neighbor with TIG or stick, he has enough work to do! The MIG wire has an 45% iron core and 55% nickel cover. I have a BBQ grill, propane torch (small and large) and a bucket of sand.

After reading some sheets, recommended pre-heat is 350 deg (might need new gloves!). and end drill the cracks.

I have to weld a hole in a heat riser, so I will try the propane to get it up over 100 deg (some videos found about that temp), weld it, then in the sand. My shielding gas is mild steel mix argon75/CO2-25. Sheets say argon95/HE5 or argon75/HE25, but Helium is used to raise the temp, something we do not want here, so I will try the CO2 and see if I get good penetration.

For the real repair, I will have to wait for the ambient air temp to improve more (its still cold in the garage), before trying larger repairs.

It is just annoying to wait for spring, I wanted to finish up this smog restore months ago! Its been one set back after another. Smog pump was tricky to de-vane, two smog tubes rusted on, bolts rusted on, now this crack. At least the pump is done, and got the smog tubes nuts out.

Now I need to repair two nuts on one smog tube, still get the lower bolts out, fab manifold plugs and after crack fix, evapo-rust the manifolds and coat.

[KevinW]

Well, not much is happening on the welding try. I have been gathering "stuff" and waiting for warmer weather. Plus spring is here which means tons of yard and garden work

I did make a box and immersed the good manifold in Evaporust. Strange thing was this yellow residue on the inside. Was able to wire brush it off, but it looked strange. Anyone else seen this yellow?

[John Brown]

Looks to be Sulphur deposits, likely from octane enhancers used by refineries.

[mhm1966]

Kevin,

I am glad you are using welding material for the USA. The stuff made in China is junk and will never provide an adequate weld. You should also make a jig to mount your exhaust manifold in so that when your done welding the holes in your exhaust manifold lineup with the threaded holes in your head.