OEM Headers: Crack & O2 Bung Repairs?

[Steve Wood]

looks nice

[~JM~]

Now 2 of the 3 sensor openings (lengthwise) are in the direct flow path. The upper portion of the third window is right at the transition of direct flow path & the bung recess. Couple of the pics are not displaying the width correctly.

[gnonyx]

Local fabricator was able to weld driver side header & swap O2 bung. I asked him to add an extra O2 bung in a location that I think will provide easier access.

The welded work looks great, but personally I would add a piece of steel to add more strength between both tubes to prevent future cracks. The photo is what I used and welded inside the header's shield area
Also since the headers has been welded you might need to check and see if the headers flange are warped, and if so check out some machine shop that will use a milling machine or use a belt sander. 

[~JM~]

I provided a spare head to use as a jig. I will check with a straight edge.

That reinforcement piece you added looks like a good idea.

[~JM~]

...Also since the headers has been welded you might need to check and see if the headers flange are warped, and if so check out some machine shop that will use a milling machine or use a belt sander. 

Driver side flange failed the straight edge check. Passenger side is OK.

[Grumpy]

I don't care what ya do to prevent cracking. THEY WILL CRACK AGAIN. Even new headers crack when your racing a car. Nature of the beast. 

[Steve Wood]

Dan, that is a good point.  I don't know many materials that will last too long being heated up to 1700 degs and then allowed to be cooled back down before the cycle is repeated.  None that I can afford....

[~JM~]

Dan, that is a good point.  I don't know many materials that will last too long being heated up to 1700 degs and then allowed to be cooled back down before the cycle is repeated.  None that I can afford....

UNOBTANIUM

[reality]

Large cars [diesels] don't seem to have a problem near as much. Do they stay hotter for longer or something?

[Steve Wood]

I did not know diesel cars used headers, but I don't guess I looked under that many hoods.  I assumed they used cast iron manifolds for long life.  For some reason, I thought exhaust temps were relatively low to our forced aspiration hot rods.

[reality]

Large car is trucker lingo for class 8 trucks,
 They get the manifolds hot and cool many times a day.
Even if they are cast, I don't see the issue if they last,
Places like Bully Dog and others can port and polish them and that brings the pyro numbers way down.
Could back pressure be part of the problem?
Could a ''proper'' cool down help?

[nocooler]

With all the aftermarket cast manifolds - turbo and n/a coming out for the LS, it might be viable for someone to do a set of stock replacement pieces in cast iron/steel/stainless. People have made well over 2000hp with the stock LS truck manifolds so flow isn't an issue if designed correctly. 

[Steve Wood]

I don't know anything about heavy trucks nor how the headers compare to the thin wall stainless headers on Buicks so some one more knowledgeable will have to answer.  I have seen many a cracked cast iron manifold off cars that had failed but I doubt that has anything to do with modern set ups.   

[ULYCYC]

When I was a fleet mgr for a very large fleet of mix use vehicles we kept a large inventory of heads and exhaust manifolds. They all crack after rough use comparable to racing like Grumpy said.  Now talk about our thin wall garbage, 35yr old stainless headers with a million heat cycles.
  No way to make them better or add any life to them. Try TA headers or maybe custom Kooks headers if you want something that may hold up a little better.