Exhaust Manifold

[88mancheman]

I know this is a widely discussed topic as I've spent the past few days going through the search function trying to find a recent answer but what is the general consensus on the "best" exhaust manifold for our Renix 4.0's? Reason I ask is I'm getting ready to replace the cracked exhaust manifold on my 4.0, I choose brown dog motor mounts to install while I'm in there to try to mitigate this whole cracked exhaust situation but I'm having a hard time deciding between manifolds.... I've done tons of research and I've kinda come down to 3 options unless someone can point me elsewhere 

I see these "OEM" replacements but I feel like why replace a cracked stock manifold with another "stock" one when it will quite possibly do the same thing

https://www.quadratec.com/products/917622_07.htm

 

I also see these Dorman ones which if I'm going to buy a stock one I'm leaning towards as its the cheapest option & they claim a lifetime warranty and that seems to tickle my fancy, but I'm not sure about build quality and have the same concerns as above... 

https://www.dormanproducts.com/p-5607-674-170.aspx

(the link I want to buy from will not post so this is the closest one but I found but I found it for about $145 shipped)

 

then comes kind of my biggest question because the above seems pretty straight forward, I also see these pacesetter headers for our renix jeeps, I really like the idea of upgrading & hopefully a tiny bit better performance even tho thats not really too realivent to me as its a jeep not a sports car lol but I'm really curious if anyone has actually ran them recently with success? I see tons of forums on both sides of the spectrum, some saying they are junk,leak,crack, egr doesn't fit, just doesn't fit in general, while others seem to be super happy with them and say they had no issues... but they all seem a little over 10 years old, and even the recent posts nobody has done a true update on them) now and I've read that they have apparently made some alterations to the design lately to make them better... is there any truth to this? Are they really worth the extra coin or should I just toss that Dorman in it and hope for the best? any other options or thought would be warmly welcomed

 

https://www.summitracing.com/parts/psm-70-1191?seid=srese1&gclid=CjwKCAiA6bvwBRBbEiwAUER6JSV9Iai8nrBUXuMe5oxyJA76VHfA2H1FplZT4D7nN1KtxOPUEbu4-xoCRaIQAvD_BwE

[Dzimm]

I can't speak for the Renix manifolds but I've used the cheapest ones I can find (found on Amazon) on 2 of my HO's and they are still holding up.  

 

For extra piece of mind add an exhaust flex section in just after the manifold to allow everything to flex without cracking.

[Eagle]

12 hours ago, Dzimm said:

 

For extra piece of mind add an exhaust flex section in just after the manifold to allow everything to flex without cracking.

 

^^^ I think this is the key.

[schardein]

My XJ and MJ are both 91, so not Renix, but...

 

I replaced both exhaust manifolds with the aftermarket type with the bellows on the outside tubes.  Both were used, pulled from junkyard vehicles, for about $30 each.  Cleaned up and installed, work fine and no problems to date.  I don't have the flex exhaust section, but it's a good idea.

[88mancheman]

Thank you guys for the responses! I managed to find this on RockAuto for $138 plus shipping

https://www.rockauto.com/en/moreinfo.php?pk=14197&cc=1181584&jsn=9

so I think ill go with @Dzimm idea of using the cheapest ones and welding in a flex pipe on the the down pipe to help the exhausts flex without cracking hopefully, I would much prefer to use @schardein idea of using the later 91 up exhaust because of the bellows on the tubes but I live in CA where we have these dumb smog laws and that would require me welding new bungs on the tubes myself for my 02 & EGR to keep my smog guy happy and I'm not a huge fan of welding headers they seem to crack right next to my welds every time. 

 

[coolwind57]

I welded the cracks and then installed gussets between I think the last couple of header primaries.  For the gussets, I just cut some triangular pieces of 1/4" flat stock I had laying around and welded them in place to further strengthen the primaries that were most prone to cracking.  You may consider this as an extra header strengthener as you're welding your cracks.  

 

Also, I did the flex pipe mod.  Here's some stuff taken from my build page that may interest you:

 

 

So today I stopped by the exhaust shop.  Got some pics. 

 

Now that I'm back up and running, I am concerned about my exhaust header cracking again.  I had welded the cracks on my header when I had it out of the vehicle and even welded on a gusset between the last two primaries.  Upon advice from the forum, I had a 6" flex pipe welded on my header pipe.  

 

Also, I wanted to address additional support (hangers) with the shop and I asked them to put an additional hanger at the bellhousing.  I had to ask what the tab bolted onto my bell housing was a few weeks ago because it did not appear to attach to anything.  Well, the guys welded on a clamp, giving the front of my exhaust system some additional support:

 

 

Additionally, a shop guy said that I was probably suppose to have one at the transmission mount.  I had no idea that there was suppose to be one there.  A PO had deleted my CAT so perhaps that's why I didn't know that anything mounted there.  Anyhow, he corrected it by installing this:

 

So, I feel much better about hitting bumps and flexing my truck now.  He charged me like $30 for parts and I think $80 labor, which I didn't feel was too bad.  I have a flux-core welder and can get by with minor welding, but I was really ok with giving this job to a pro.  I feel it paid off as I learned a thing or two from them today.