I’m mid way through the swap, have my engine delivered waiting till monday. I noticed the exhaust manifold on my 2006 was cracked in the tube comming off the rear cylinder. Likely all the way around. I welded the outward facing half today with 55% nickel 45% iron electrodes and it went well. I’ll do the second half when it is out. I’ve read that it will bold up to the 2007 head. Some people warn about leaks around the flanges, but the same warnings are abundant without any swap. Is it correct that this 2006 manifold with at least bolt up and work? I know it won’t run to the potential of the 2007(potentially as I have a straight pipe instead of the second cat).

My other question is related but if I were to buy the Magnaflow header for the 2007, since that is what the engine is, I’ve heard that there is alignment issue with the tubing after the first cat built into the manifold and that flex tubing is used in that case. The flange from the manifold to the exhaust tubing has a special rounded bushing. I am not sure how it would all bolt up if using flex tubing if it is in fact needed?

Also, on the replacement engine, I noticed black soot around the exhaust port for cylinder 5(rearmost). I was told that it might be a leak from a warped header. You can see it in the pic of the engine I uploaded. - Anything to worry about or is it being taken care of with new gasket?

I added pics of the rig I got the engine out of. A 2007 grey H3 out of Texas with 66,000 miles. Theres some identifying stickers on it. If it’s yours thanks, I think.

Also added pics of my poor weld job. It’s not as porous as it looks That is from pining it while it is cooling to prevent cracking. and i think theres still schlag on it in those pics. Haven’t welded in 2 years. I had to do it in the parking lot standing on my generator. Pretty hard to get in there. A Dremel with a thin grinding disk and/or a thin cone shaped drinker is all you need to v grove prep, i also used a grinding disk that is about twice as thick as those reinforced cutting disks. That went very fast.. I used an angle grinder to surface prep where I could fit the grinder. It was difficult.


I’ll next be doing a mod I saw years ago opening up the port for the airbox to a larger diameter pipe going to the fender. Im running a drop in K&N. Don’t think I’ll do a full cold air system since the H3 already has one, it’s just restricted from that port. Then possibly magnaflow, my straight pipe in the rear and then a tune from PCM of NC formerly PCM for less or whatever unless there is other options. He told me for the direct swap he just adjusted the air/fuel tables and a bit of spark. I’ll have to check if he has stuff on file for the additional mods Im doing. I was told the stock ecu has a 25% built in adjustment for A/F and it’d run fine under normal load, but it would likely spark timing or whatever under heavey load or heat due to different cams.

 

What i found out is the magnaflow has several different models. The worst flowing one is the one for 2007+ California. It is a cast flange and runner unit while the 2006 version and all of the epa versions are the mandrel bent steel. California forced them to copy the original design in 2007 or something and the manifold flange ports are actually smaller/more restrictive. Both Federal grades fit all years and has the same design as the 2006 California head, so for easy compliance, I bought the 2006 manifold even though its going on the 2007 motor. This will give me easy compliance if I ever tell the dmv i did the swap. According to the smog referee I spoke with, mainiaining the 2006 cats and ecu means i am making the 2007 conform to the 2006 vehicle, so this isnt a motor change, it is a motor replacement and it will be treated as a 2006. Otherwise, the entire emissions system, ecu, everything would have to be changed to a 2007 to pass a referee inspection IF it was ever required.

As long as there are no codes and the regular smog check guy doesnt make a fuss or doesnt know, the smog check computer will simply ask the car’s ect “Are you happy and all sensors and trims within a normal range that doesn’t throw a code?” Then it will pass.

Id recommend doing your own research and buying the 2006 magnaflow or federal OEM grade if doing the swap and needing a manifold, otherwise, a 2007 junk yard one would work as well as long as the smog tech doesnt snoop around a lot as it’s hidden under the heat shield. There are definatly downsides to using a 2007+ as it could have the additional O2 sensors bungs and they’d ask questions or see blocked off ports, raising flags. The 2006 is the easiest to get smogged as there are only 2 sensors. One in the front and one in the back, so both cats arent monitored individually. Just the one at the end needs to be happy, so you could possibly get buy with only one good cat(I think I did previously), just replaced the secondary right before a smog.

Anyway, it’s going to be a 2007 motor, magnaflow manifold and I’ll open the airbox port to the outside up a bit to increase flow into the airbox and have a K&N filter in there a tune and Theres some other things going on in the exhaust but I’ll leave that out. I’ll switch most of the airflow things back to stocking a week or so before a smog check to bring air/fuel trims back into a more restrictive level.

 

The swap is complete and the 2006 magnaflow California certified exhaust manifold is on and fit correctly. If anyone ever does this swap, you want to order the 2006 California manifold. Not the 2007. It’s a cast unit that appears to have restriction built into it to comply with California regulations while the 2006 uses the base design for all of the other versions. Ca introduced new requirements sometime in 07-08 for these H3s and emissions in general that the cat /manifold had to conform to OEM spec. It’s why there’s 2 o2 sensors in the 2006 H3 system and abd sometimes 3 in later years.

you also want to do it this way because then your H3 will conform to the original 2006 model year. A smog ref told me It qualifies as an engine replacement not swap. So no hoops to jump through.

even better news, even with the 2006 PCM running the new 2007 motor, a magnaflow exhaust manifold on and the Secondary catalytic converter removed entirely, my long term, short term, timing and o2 sensor readings are all within normal range without tuning.

this thing would pass a computer only smog test even without the second catalytic converter installed. The H3’s computer is saying everything’s good. The dip in the o2 sensor readings is a blip of the throttle.

no reason to tell anyone you did the swap




Timing advance was about +9

To be 100% honest. Ive only put about 20-30 miles on it over a few drive cycles and have been taking it easy, it feels better lie its not tripping over its own feet anymore, I can feel the additional torque but it isn’t overwhelming, its just better. I think I noticed power and throttle response removing the second cat just as much as the additional torque I am noticing with the engine swap and the manifold Each is incremental. I might still get it tuned. I’m not sure of the gains from it. We’ll see.

 

Thanks 😊. Always good to have more information.