Exhaust Manifolds that crack

[VX L67 Getrag]

Has anyone every had any luck with welding cast exhaust manifolds that crack, I was told it happens because the cast starts to crystallize & welding would only work for a short time?

It's also strange that it only seems to mainly happen in Toyota vehicles, so guessing it must be the material hey make them out of or something?

[festy]

Alfettas came with factory cast headers which are very prone to cracking.
CI is brittle at the best of times - and without any form of flex joint in the exhaust, just touching the exhaust on a tall speed bump would crack the header
I've had some success brazing CI, but it's such a PITA - just when you think you've got it perfect and it starts to cool you hear a little 'ping' and it cracks again... so you swear a bit ,and start all over again
I've successfully fusion welded *one* piece of CI, but it was so frustrating and time consuming that I haven't tried it since.

I think the comment on crystallizing might have been about the welding process. You need very precise pre-heating and controlled cool down, otherwise the CI crystallizes at different rates and immediately cracks.
There is another process for repairing CI cracks called cold stitching, it's only slightly cheaper than gold plating your headers, and that's if you can find someone alive who still knows how to do it...

[HQ355]

At work we have a torch that replaces the standard oxy torch (looks same as oxy torch but has a spray gun type canister hanging from it) all you do is fill up the canister with this special powdered metal, heat the cast iron up until it's vfh and push the lever on the torch. When you push the lever it lets out the powdered metal and it welds onto the cast. My boss welded up a set of cracked cast iron heads go his mates race car and he's had no dramas with it since, it works really well

[Gareth]

We've had plenty repaired over the years by our local engineering company, pretty good success too.

The cause is the big issue, poor cam timing/tune = overheated manifolds, poor exhaust hangers will often give the same result. If they have been welded properly and the cause has been fixed, they won't crack again.

[delcowizzid]

the first cast manifolds from VP v6's would allways crack the passenger manifold VR it seemed to be corrected.couldnt find a good passenger manifold for under 300 bucks in NZ when i tried so on went headers LOL

[immortality]

LOL, I remember enquiring about V6 headers and the first question I got "cracked manifold?".

[vlad01]

the first cast manifolds from VP v6's would allways crack the passenger manifold VR it seemed to be corrected.couldnt find a good passenger manifold for under 300 bucks in NZ when i tried so on went headers LOL

I've come across my fist cracked manifolds on the latest VP I stripped, never seen it before. its both sides, one side was repaired.

[Charlescrown]

It depends on the material. Grey or white cast. One cannot be welded one can. I don't know the difference. HQ355 is on the money with the correct method of repair. I have MIG welded many manifolds with steel wire and they haven't cracked yet after many years.

[VL400]

I have had limited success welding cast. Drilling a hole to stop the crack, V groove it, heat, weld with 309 filler and then cool slowly wrapped in a fire blanket. Sometimes it works, othertimes you hear the crack as soon the pedal is released

There is an old school method of drilling along the crack and then peening bolts in. Trying to find a video but not been sucessful yet...

HQ355: Sounds like a neat setup!

[Holden202T]

I don't think I have ever seen a commodore V6 motor that hasn't had at least one side cracked!