Can these headers be repaired?

[JDMac34]

While my engine is out for the second time, I'm checking every little part that can affect its performance. I installed the new engine a few weeks ago and had misfire and fuel trim balance issues that I could not figure out. Shaun from AED kept saying that the fuel trim issues were likely due to exhaust leaks. I couldn't find any exhaust leaks with the engine in the car, but I had a few leaky valves that warranted the engine to be pulled out again.

Now that the engine is out and the headers have been removed, I found a decent crack in each header. These are Kooks headers and were on the car when I purchased it a few years ago. I have reached out to Kooks to see what they say but wanted to get the opinions of everybody here too.

Primary tube crack at flange (left header)

Left header flange (dirty then after being scrubbed with a ScotchBrite pad) Just about all ports looked like this for both headers


Crack at collector (right header)


I made a plate with the same hole pattern as what's on the heads. Using an OEM gasket, I bolted that plate to the flange to seal that end of the header. I sealed the other end of the header at the ball socket and hooked up 15 psi of shop air to pressure test the headers with soapy water. Results are below.

Left header pressure test

Right header pressure test

I was not expecting to see air leaking between every flange-to-primary tube joint. I was originally thinking that the groove around each port in the flange pictures were just from carbon buildup, but now I'm worried that every joint is cracked.

Is my pressure-testing method reasonable? If all of these joints were rewelded, what are the chances of these cracking again? Are these worth trying to fix, or should I just bite the bullet and buy another set?

 

[GAR944]

Is my pressure-testing method reasonable? If all of these joints were rewelded, what are the chances of these cracking again? Are these worth trying to fix, or should I just bite the bullet and buy another set?

They will crack again, usually right beside where they were welded. Nature of welding changes the properties of the material and tends to make it brittle. Biggest issue trying to repair is you cant get the material properly clean beforehand so think of it as a patch job. How long will the patch hold?? My exhaust system grow about 1/2 inch according to the melted plastic on the rear bumper. They do cop an absolute hiding on track cars so consider it a maintenance job. Have been told to expect my mufflers to peal apart at some point on the track.

My understanding of the primary to flange weld only being stitch welded is due to the large difference in material thickness and therefore difference in expansion rates. If they fully welded that joint they would risk cracking very quickly.

 

[blacksheep-1]

We weld them on the Gt4 all the time. Unfortunately higher quality, high performance and light headers are very prone to this type of cracking. The old school crappy $100.00 Hedman never had these problems but were never the performance quality of these.
There used to be " race headers" and
" street headers" and were not the same. Now days that line has blurred .

 

[Mad Hatter]

Yup my Kooks had the same exact problem. Welding them up only lasted a race or two.

 

[JDMac34]

Looks like I'll bite the bullet and buy a new set. I'd prefer to stay with Kooks so that I don't need to get a new midpipe, but is there a significantly better option?

 

[Fabman]

Looks like I'll bite the bullet and buy a new set. I'd prefer to stay with Kooks so that I don't need to get a new midpipe, but is there a significantly better option?

American racing headers.

 

[Mad Hatter]

Since the death of my Kooks. Bought a cheapo ebay longtube header and welded on a proper merge collector. Surprisingly enough... they are lasting longer and give more HP....Who would have thought!!. the cost is about US$250 for the LTH and another 250 for a pair of collectors.

 

[blacksheep-1]

Yep, I was gonna say try American Racing Headers

 

[302BOB]

MH, Sometimes being a cheapskate pays off.....don't ask me how I know..............

 

[Mad Hatter]

Nothing cheap about this hobby! Every little savings is then spent on some other expensive item

 

[thelostotter]

Everyone is suggesting ARH but I've had an issue with them too though it was much more manageable than yours. I've had the rear O2 bung on the passenger side crack three times. Their mid pipe angles the rear O2 bungs directly into the Blowfish shifter bracket so I had to use 90 degree adapters on both rear O2 sensors, maybe this caused the issue, not sure, but the driver side never cracked once. They paid for me getting it fixed locally the first time. The second time they sent me a new x-pipe and I had to pay to ship the bad one back. The new one cracked within the first week in the same exact spot.

At this point I was tired of the back and forth so I cutout the entire ARH weld and formed stainless patches that relocated the O2s horizontally and had a local guy TIG weld them on. Nicest welds on the exhaust now and no more cracks.

Personally I find the Kooks headers pretty appealing due to the bolted joint. ARH slip fit connections are a bear.

 

[Fabman]

a lot of times cracks in headers are from the way the exhaust system is hung. If its pulled up too much or hangs down relative to the headers or stressed in any way it will never stop cracking. The exhaust has to be in a neutral stress point when its hung. I ran a muffler chain for years back in the day and this is a super common problem.

 

[honeybadger]

also suggest the ARH headers - I really don't think you'll have an issue. I've put mine through plenty of heat while wrapped in DEI heat wrap and they're still crack-free. Personally, if it's a race car and you're not running cats, I would add their resonators. Long tubes without cats and straight exhaust is super raspy on a coyote. bit too much, IMHO