Headers ?

Thinking about headers and cat back muffler system for the 3VZE.

Question,

You guys that have done it, how are you dealing with state emissions control ? I’m in Nevada, Clark county so the state requires an smog check every year.

I was exempt with Classic Vehicle plates, because of covid I couldn’t get in on time for a mileage statement last year and had to do smog to keep my 4Runner registered.

So right now I’m guessing to get my exemption back I will have to smog again this year, which basically means the tech will also look for modifications while the truck is on the machine.

What happens to the O2 sensors and catalytic converter when you do headers ?

Appreciate your input.

 

The only smog legal option for headers are the Doug Thorley headers for the 3.0 L. Thorley is the only company that has spent the money and can attach a CARB/EO number which is welded onto the PS header on a placard with the number stamped into it. A competent inspection station will be looking for this CARB/EO number. The problem is the Thorley headers are very expensive at $700 because they hold this distinction from all the rest. So having taken this painful plunge I had to pitch the slip joints and the U-bolt clamps and replace these joints from the header/s to the collector Y pipe with turbo flanges to stop air leaks getting to the O2 sensor even though it is not a wide band sensor on the OBD1 smog system. I also cut the OEM O2 sensor bung from the exhaust and welded that into the Y-collector in front of a nice big 2-1/2" Magna Flow CAT that is CARB legal for my 91 4Runner. I backed that up with a custom made 2-1/2" Flow-FX offset muffler and recreated the OEM support system with some 3/8 steel rod. All this along with an OEM Denso oxygen sensor gets it to pass the smog test both visually and mechanically.



The only thing that still is a mystery is that the engine runs much stronger and pulls like a Clydesdale to 100 MPH when I set the static timing to 14° rather than 10°. But I set it to 10° for the smog test as that is what the sticker under the bonnet says the timing must be. I did not use the supplied adapter that the header kit comes with because it is necked down to feed into the OEM CAT and has the bung on it for the O2 sensor. I am currently running a Flow Master HP-2 in place of the CAT until its test time and the small amount of back pressure the HP-2 provides seems to improve the drivability since it has to produce a bit of back pressure and I loose a little top end speed but it is quieter yet has a very nice exhaust note.

If California will make the requirement for a smog test be a revolving time scale of 30 some years back then these 2nd Gens will start to become exempt like my 1973 Jensen Healy already is. If that happens the air injection and EGR will be removed from the header and the plenum and I won't have to spend $70 every other year for a test.

 

Thank you Andrew, good info. There’s a set of those headers on our local Offerup, the guy is asking $500.

I’m curious though, if you get the exemption.....do they restrict your yearly mileage ? You have to now go into DMV and sign a mileage statement at registration time.

Here in Nevada for any smog exempt vehicle, no more than 5000 miles regardless of vehicle type for instance. That’s strictly Cars and Trucks driving on the freeway etc.

If you exceed that limit, you must smog.

 

Not exactly true for Nevada... That rule is for non-compliant areas (Washoe and Clark Counties), not the rest of us.