Installing headers, keep the front cat or delete?

On my 02 V6 (two cat converters) I have a blown head gasket between cylinders 3 and 5 as well as an intake valve not seating correctly on cylinder 3. I’ve decided to buy two refurbished, and complete, heads and add headers since I’ll be down to the block for the repair. I bought the OBX headers (look just like JBA) and I need some input on what to do with the front cat. Do I just delete it and make a flange from the header outlet to the rear cat? Pics of similar set ups would be helpful and appreciated.

 

I don’t know about obx but I read somewhere that they were knock offs of the TRD headers that were offered for the 1st gens.(obx might even have made them for TRD?) <—-someone said that on another website but I never researched it.

If they are vehicle/year specific then the y-pipe should correspond to the 2 cat system. If the y-pipe is designed for a one cat system then I’m not sure if that rear cat can bolt up to it? I lucked out and found some TRD headers that were available on EBay a couple of years ago. I then found the y-pipe that corresponded to the 99-04 Tacoma’s. I ended up having my local exhaust shop cut off the three bolt flange and weld up a two bolt flange on the front cat so that I could bolt up the y-pipe (which came with a two bolt flange) to the cat. Sorry no pics but the old exhaust manifold next to the TRD system. It would only help you if the obx system is a replica of the TRD. (I’ve read that somewhere but someone could have been blowing smoke) I hope any of this helps. I spoke with a bunch of people and the only bit of advice I can give I wish I took sooner was cut off the exhaust manifold from the y-pipe. It’s not worth your time trying to remove it unless your vehicle has zero rust. I lost about four hours of my life trying to remove it by breaking free the extremely rusted bolts.

 

The 2nd pic is the y-pipe on the right that came with my headers. I then had someone on here find me the Toyota part # for the 99-04 y-pipe (seen in pic to the left)and miraculously found one in an old parts warehouse that was lying on a shelf for years and years.

 

In the very last picture, you can see that on the headers there is a spot to mount the AFR sensor. On the manifold setup, the AFR mount is on the forward cat converter. The question is did you delete the cat or weld in a universal one?

 

the only advice I can/could have given was to pull the vacuum booster for the brakes off, leave the MC and lines attached, just take the booster off. It seems kind of crazy but after you have done it once you will do it every time, there is THAT much more room imho.

 

I’m not concerned about room. The question is about whether or not to keep the front cat. But thanks for the input.

 

I did not delete the cat because I had a y-pipe that corresponded to the two cat set up. If I was stuck with the y-pipe that my headers came with, I would of had to delete the forward cat and get a URD o2 sensor simulator. As soon as you delete that forward cat you will throw a code. Here is a link to the o2 sensor simulator if you should ever need it.

https://www.urdusa.com/urd-rear-o2-simulator-5vz-fe-3-4l-v6/

 

Toyota’s are extremely sensitive when it comes to catalytic converters. If they dip below 95% I believe it throws the CEL code. Both my cats were 15 years old and threw the p0420 code. I tried replacing both cats with Magnaflow. I had to reuse my forward stock one due to fitment issues with the Magnaflow. After a month it threw the code again. Eventually I’ll replace both with oem ones but at a grand a piece I’m in no rush. Right now the URD o2 sensor simulator keeps my CEL off.

 

Rather your obx y-pipe that came with the headers is designed for a 95-98 and is longer which was a one cat set up or it’s designed for 99-04 Tacoma’s and it’s shorter and set up for a two cat set up.

 

I just edited something I messed up above. Concerning the pic with both y-pipes. The longer one came with my headers. It was designed for the 95-98’s, a one cat system. It’s longer so that it can reach the one cat which would be further back due to not having both cats. I’d call obx and find out if the y-pipe that came with your headers are designed for an ‘02. If so, the only question is did they come with a two bolt flange or a three bolt flange? If it’s a three bolt flange your golden, if not just cut off the three bolt flange on your cat. A local exhaust shop has dozens of flanges, they should have a two bolt flange they can sell you.

 

@BeLance89 Here's a question for you about the rebuilt heads. In days gone by when I was a Chevy man, I rebuilt the engine in my 1969 El Camino. I didn't realize at the time that they use old valve springs with spacers. Causes too much stress on springs with aftermarket cam.(I broke 2 intake Springs). Later I learned to request heads with all new springs. Don't know if this will be a problem on the Taco, just throwing out this information.

 

Perfect! I’ll keep the forward can then and have an exhaust shop weld a flange on. And if I get a CEL I’ll pick up the URD thing-a-ma-jig.

 

Exhaust manifold gasket. If you didn’t want to spend $70+ Yotashop (below has the gaskets for I think $30.

https://www.ebay.com/i/232771028590?chn=ps&ul_ref=https%3A%2F%2Frover.ebay.com%2Frover%2F1%2F711-117182-37290-0%2F2%3Fmpre%3Dhttps%253A%252F%252Fwww.ebay.com%252Fi%252F232771028590%253Fchn%253Dps%26itemid%3D232771028590%26targetid%3D484372160079%26device%3Dm%26adtype%3Dpla%26googleloc%3D9025181%26poi%3D%26campaignid%3D1498383093%26adgroupid%3D60666402667%26rlsatarget%3Dpla-484372160079%26abcId%3D1139446%26merchantid%3D6499004%26gclid%3DCjwKCAiAqaTjBRAdEiwAOdx9xiJ-pPS9FoFeIfnhaoMRm6bUA9fdPV8T8ObKu16MwUdpuighzCXLxRoCoXIQAvD_BwE%26srcrot%3D711-117182-37290-0%26rvr_id%3D1862313482022%26rvr_ts%3Dfe50e14b1680ac3d95d542adfffc0596

 

Exhaust studs

https://www.yotashop.com/toyota-2-4l-2-7l-3-0l-3-4l-88-04-oem-exhaust-stud-nut-kit-kit-1005/

 

Also if OBX didn’t give you donut gaskets, your going to need them for the three y-pipe connections.

 

Picked all that up already I didn’t want to wrestle for hours getting nowhere with the rusty exhaust studs on the stock heads it’ll be nice to buzz some new studs onto the fresh heads.