2nd Gen 4Runner Exhaust Questions (1 Viewer)

[2Mechanical]

Gentlemen - first post here, hoping somebody can help me out. Thanks in advance!

I'm planning out a new exhaust system for my '90 4Runner 22RE.

My current exhaust (from PO) looks like a high school kid's first welding project and its seen a few rocks too. Its a complete hack job - from the pipe welded straight to my Thorley header, to the leaky booger-welded half-a$$ O2 sensor flange - not to mention the lack of a catalytic converter. I live in Cali sooooo...

I will be putting together a completely new system from the header - back, including a new high-flow cat to keep the smog nazis happy and minimize the exhaust smell when my back window is down.

Question: From pictures online, I see that the stock cat location is pretty far back - near where the output flange of a single xfer case would be. California smog requires the cat to be in its stock location (or very close) so I need to know how far back to position the new cat. Can somebody take a quick measurement on their rig and let me know - maybe from the engine block / bellhousing interface to the center of the cat?

Same question on the O2 sensor - although I am pretty sure that it should be as close as possible to the header collector / flange and ideally it would be mounted vertically (please correct me if I am wrong).

Thanks for the help!

 

[2ndGenToyotaFan]

My cat starts just before the rear of my T-case, and extends past it, probably 1/3 and 2/3's. O2 sensor is just under drivers seat in the vertical position I think..... I'm not looking at the truck right now... Good luck!

 

[2Mechanical]

2ndGenToyotaFan - thanks for the response! I'll definitely need some luck to finish this one out.

 

[pappy]

As far as the cat, there should be a heat shield under the seat. The cat lines up with that.

 

[2Mechanical]

I appreciate the responses. Have not noticed another heat shield under there but I will look when I get back from the holiday weekend.

 

[ntsqd]

Most important is to make the system look old before inspection day. If you're about to need to smog it wait until after you pass to start on this project. Give yourself 2 years to properly age the system......

I get welding directly to the collector. those flanges always seem to leak. I used a flex section with a Stainless over-braid right at the collector flange to eliminate the leverage the system had on that joint. Seemed like the engine moving about as it does under load would try to pry that joint apart. The flex section changed all of that. I also added a 'liner' to the joint. Used a piece of exhaust tubing about 2" long and slit it length-wise, and then cut it again parallel to the first cut so I could close it down (used a hose clamp to do that) *just* enough to allow it to barely fit inside the collector tube. Then I welded it into the collector using 3 or 4 rosette welds and leaving about an inch sticking out. The head pipe was clearanced to fit over the tube stub. After that all I ever needed to seal that joint was a bead of high temp RTV around the tube stub at the flange. Oh, use brass nuts on those collector flange bolts with flat washers only. Lock washers make things worse and they are not needed. In almost 20 years I never had a brass nut loosen and I was hard on that truck.

CAD generated jpg showing what you're trying to create with the tube stub, flow is always from the side with the stub to the side without.

Exhaust flex section like this:
Summit Racing® Flex Joint Pipes SUM-643022