Header off from Modified race engine. PICS

[tig1]

This was off a Modified dirt track race engine where one of the tubes cracked.

 

[Revving2Redline]

Too hot?

 

[CT8]

Vibration and or thermal expansion

 

[A_Harman]

Constrained thermal fatigue. It will crack again in the heat affected zone adjacent to the weld repair.

 

[P10crew]

Originally Posted by A_Harman

Constrained thermal fatigue. It will crack again in the heat affected zone adjacent to the weld repair.

^ This right here guaranteed

 

[tig1]

Originally Posted by A_Harman

Constrained thermal fatigue. It will crack again in the heat affected zone adjacent to the weld repair.

My customer has three dirt track race cars and I know him. If it breaks again I will pass that on to you. I actually have more confidence with this repair. My take is that the area passing by the bolt hole wasn't welded to begin with. Notice the other tubes. So I welded this one as you can see.

 

[A_Harman]

Maybe you can oven bake the header at 400F to temper the heat affected zone and reduce the possibility there is Hydrogen embrittlement.

 

[tig1]

Originally Posted by A_Harman

Maybe you can oven bake the header at 400F to temper the heat affected zone and reduce the possibility there is Hydrogen embrittlement.

Oven bake a header this size?? Lets not over think this.

 

[ccs368]

Is that weld bead going to cause issues with properly tightening a nut or bolt on that flange?

 

[Cujet]

Slip joints are a great way to stop such cracking.

 

[tig1]

Originally Posted by Cujet

Slip joints are a great way to stop such cracking.

But that wouldn't help in this case.

 

[tig1]

Originally Posted by ccs368

Is that weld bead going to cause issues with properly tightening a nut or bolt on that flange?

No, not shown in this pic was I ground out that area with a cut off wheel for the head of the bolt to clear.

 

[RazorsEdge]

Don't buy cheap headers and this won't be a problem. I've installed so many sets of headers, shorty and long tubes and never had this issue.

 

[Fitter30]

Wonder if welding on a piece of angle iron lenghtwise would change the harmonics of that tube.

 

[Cujet]

Originally Posted by tig1

Originally Posted by Cujet

Slip joints are a great way to stop such cracking.

But that wouldn't help in this case.

I do believe it would solve the problem. Such cracking is created by stress. The use of slip joints eliminates the high stresses created by thermal cycles and vibration. I deal with aircraft exhaust and race car/turbocharged engine equal length headers all the time, and see the same type of problems over and over. The slip joint is the solution. Quiz: Which pipe cracks in the picture below? [img]https://resources.globalair.com/images/article/a0750130-6.jpg?w=650[/img]

 

[tig1]

Originally Posted by RazorsEdge

Don't buy cheap headers and this won't be a problem. I've installed so many sets of headers, shorty and long tubes and never had this issue.

My customer races three cars on various dirt tracks, including Tri City Speedway in Granite City,Il. This didn't happen to him until it happened.

 

[spasm3]

Originally Posted by Cujet

Originally Posted by tig1

Originally Posted by Cujet

Slip joints are a great way to stop such cracking.

But that wouldn't help in this case.

I do believe it would solve the problem. Such cracking is created by stress. The use of slip joints eliminates the high stresses created by thermal cycles and vibration. I deal with aircraft exhaust and race car/turbocharged engine equal length headers all the time, and see the same type of problems over and over. The slip joint is the solution. Quiz: Which pipe cracks in the picture below? [img]https://resources.globalair.com/images/article/a0750130-6.jpg?w=650[/img]

I'm going to say the one in the middle.