Motorhead X Posted July 20, 2017 Share Posted July 20, 2017 I've been digging into my recently purchased '91 4.0 HO, working to get the recurring exhaust smell troubleshot. It was obvious immediately that the tailpipe and muffler were toast, but after getting them replaced, I was still getting fumes. I finally determined for sure the exhaust manifold is cracked by sticking a mirror and a flashlight in there for a detailed inspection this morning (After two mechanics and a muffler shop said it was fine). The truck has not been registered in California yet. It still has almost a year left on a Georgia plate registration. Here in CA we have C.A.R.B. which typically only allows the stock (more restricted) manifold design. I am all for clean air and smog sucks, but I don't understand how increasing the efficiency of a motor by improving the flow design on a header makes for significantly more exhaust particles. Maybe someone has an answer... More importantly, does anyone have any experience with getting an inspection in CA? I'm sure the stock design with the improved materials/welds will work fine, however I always install the best performing and highest quality parts I can find within reason. Wondering if anyone has any suggestions on which header to use or if there is something I am missing... I've found about six or seven different designs so far on Amazon, Ebay, and the like, but only a few stock designs that are C.A.R.B certified... Also, will a redesigned, less restrictive header increase the chances of failing a smog? I'm guessing that it might fail a smog with the cracked header on it now. Thanks everyone... :cheers: Link to comment Share on other sites More sharing options...
fiatslug87 Posted July 20, 2017 Share Posted July 20, 2017 There are CARB approved headers, search Summit Racing find the one you like and look for a better price. Do not take the chance of using a non-CARB compliant header, never know how picky the smog tech will be, you don't want to pull the intake again. Link to comment Share on other sites More sharing options...
Motorhead X Posted July 20, 2017 Author Share Posted July 20, 2017 Yeah... they are pretty much all the same design for C.A.R.B. compliant. If someone knows of any others, please let me know. Link to comment Share on other sites More sharing options...
FrankTheDog Posted July 22, 2017 Share Posted July 22, 2017 Stock header isn't that restrictive on a stock motor. Just get one like the one pictured and you'll be good to go. Or just have the one on it welded up. I have put over 100k on a welded up stock manifold. Link to comment Share on other sites More sharing options...
jeeppapa Posted July 22, 2017 Share Posted July 22, 2017 Agreed, your just not going to get a whole lot more out of it by going with a header. I would get it welded and slap it back on. Put the money that you would spend on your header into some 4 port injectors. You'll get allot more bag for your buck or get a less restrictive air intake. The injectors is where you'll really notice a difference. I've got a cracked one that is going to get welded and put on my 88. The flow on that design was pretty good out of the factory. Just my though on it. Sent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
johnj92131 Posted July 22, 2017 Share Posted July 22, 2017 My stock header was welded a couple of times before I finally replaced it with the design pictured above. I had no issue with the smog inspection once the new header was on the truck. Link to comment Share on other sites More sharing options...
Motorhead X Posted July 23, 2017 Author Share Posted July 23, 2017 Hey, thanks for the replies everyone... Yesterday morning (before I read everyone's suggestions) I gave myself a late birthday present and purchased a Banks Revolver 51327 header. It's probably way more performance than this motor requires, as you have all noted, but what the heck, I already ordered it and it's CARB legal. I'll do the 4 port injectors too as soon as I can. Hopefully the header install will go well and looking forward to driving around without getting gassed. Does everyone's down pipe have this crease towards the front, just after the header connection? I can't tell if this is stock, or if the previous owner landed on a rock or something. Link to comment Share on other sites More sharing options...
75sv1 Posted July 23, 2017 Share Posted July 23, 2017 That dent is stock. You might look at Walker or other replacement down pipes. Then again, I do not know if the Banks requires a 'custom' down pipe. I just put on a Doug Thorley. You can weld on their adapter or have custom down pipe made up. I cobbled something to get mine running. I still plan or need to have a custom one made. I was quoted $200. Link to comment Share on other sites More sharing options...
HOrnbrod Posted July 23, 2017 Share Posted July 23, 2017 The Banks header collector end bolts directly to the stock MJ exhaust pipe. Link to comment Share on other sites More sharing options...
Motorhead X Posted July 23, 2017 Author Share Posted July 23, 2017 Thanks for that info 75sv1 and HOrnbrod. I may pick up a Walker pipe so the whole exhaust is fairly complete. :thumbsup: Link to comment Share on other sites More sharing options...
75sv1 Posted July 24, 2017 Share Posted July 24, 2017 I should also add that the 'dent' can cost you power. The Walker might not have the dent. I think Omix or one of the others might not either. Might be stainless, but a lot more money. Let us know how the Banks Revolver works out. Almost went that route. The Thorley is ceramic coated, that was a deciding factor for me. Link to comment Share on other sites More sharing options...
Motorhead X Posted July 27, 2017 Author Share Posted July 27, 2017 Yep... Here's the Walker, it looks like it is free flowing and for around 45 bones. I would like (insert muffler shop here) to put a flex pipe in and I should probably replace the motor mounts too when I can. I get a nice little torque release "clunk" when I let off the gas at around 65 mph. I bet something is getting loosey goosey and I don't feel like replacing headers all that often. That four bolt connection at the tail end of the down pipe is a weld spot right? I have no experience welding. Link to comment Share on other sites More sharing options...
75sv1 Posted July 27, 2017 Share Posted July 27, 2017 I can't remember what my '88 MJ has at the cat. My '98 XJ is a slip fit. Link to comment Share on other sites More sharing options...
Motorhead X Posted July 28, 2017 Author Share Posted July 28, 2017 Well... It's not Jay Leno's garage, but it will have to do for this header job. At least there is a slight breeze lately. Link to comment Share on other sites More sharing options...
Motorhead X Posted August 19, 2017 Author Share Posted August 19, 2017 Figured I would post an update regarding the Banks Revolver exhaust. So far it has been good. I have noticed a slight increase in power, but I'm still using the stock down pipe that has the "kink" in it. That pipe is probably causing some back pressure, so I have it on my list to replace. It sounds pretty good too. Installation was a bit tricky. I actually had both the exhaust and the intake manifold on at one point with bolts hand tightened, while my girlfriend was helping me, and I had to pull them both off because the header wasn't sitting flush. I made her a bit late for work. :doh: I would not attempt this installation without a second person to help. One bolt is in a place where it is impossible to use a torque wrench and it is the first bolt in the process to tighten, but I got through it and all seems well. I also had the motor mounts replaced and noticed the motor is operating much "tighter" all around and I am hoping it helps the header last longer. Prior to replacing the motor mounts I was experiencing a thud when letting off the gas around 65 mph. :cheers: Link to comment Share on other sites More sharing options...
Crash Posted August 19, 2017 Share Posted August 19, 2017 Adding a piece of flex pipe in the crossover of downpipe will help prevent cracks/failures Sent from my SM-N910T using Tapatalk Link to comment Share on other sites More sharing options...
HOrnbrod Posted August 19, 2017 Share Posted August 19, 2017 ^^^ This. It will help.......... Link to comment Share on other sites More sharing options...
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