2.25" Stroker Exhaust Manifold / Exhaust System Recommendations

[etnlvn]

Good Evening All,

I'm spanking new to the forum but really excited about drawing from the community's knowledge and experience. I own an '06 Jeep TJ Rubicon with a recent, and perhaps inevitable, cracked head. I've made a few decisions: first, my old 4.0 is out. I'm replacing with a stroker. I've also decided to go with S&J Engines out of Spokane Valley, WA. I'm going with their updated head as well as the COMP Cams Xtreme 4x4, Hydraulic Flat Tappet; 205 Int./213 Exh. at 0.050 in., 0.450 Int./0.450 Exh. Lift;113 Lobe Sep 205/213; Torque/Throttle Improve; (EFI w/OEM Head), and the COMP Cams High Energy Timing Set. I think I have all, or at least most, of the related questioned resolved except, for the exhaust system. I'm less concerned about sound than I am providing the right amount of airflow. It's easier to find the right 2.25" exhaust system but not sure about which exhaust manifold to mate it up with. I've read too many negative articles about cracking in Banks exhaust manifolds to confidently pull the trigger on their product. I've looked at other exhaust manifold manufacturers but it can be overwhelming. So my question to the community is: what's your experience and/or recommendations for the ideal stroker exhaust system. Thanks in advance for your engagement.

[Cheromaniac]

It depends on the spec of your stroker engine. Ford a mild 4.6 that puts out up to 250hp (crank), a 2.5" exhaust from the header collector back would suffice.

[mpgMike]

If you are in California (or one of those other states with emissions requirements), you should probably use your stock manifolds. Having mandrel bends in the exhaust will reduce restriction. The specs provided suggest more of a low-end torque/fuel economy build. You won't need a bunch of flow; and in fact, a large diameter exhaust will hurt your usable RPM range power. Stock exhaust manifold should be adequate, even for a stroker. (I have a low-end torque 4.6 stroker in my '95 ZJ and use stock exhaust with no complaints.)

[etnlvn]

Great feedback. Thank you!

[SCRMBLDXJ]

I can offer some info here from my experience... I had a 4.0L in a 2006 LJ. I installed a set of ceramic coated Doug Thorley SS 3-to-2 headers for the dual cat factory '06 exhaust, along with a Magnaflow 93649 cat and a MBRP 409 SS 2.5" exhaust. I added new rubber hangers and checked the frame hangers while I was there. I wanted to fix the exhaust and not worry about it for years, so I dumped $$$ into new, quality/expensive parts...

Note - I already had Brown Dog motor mounts and a poly trans mount so the exhaust should not have been moving much, and the motor definitely had less movement than in stock form. The motor also had a 62mm throttle body, AEM cold air intake and no other mods.

The Thorley headers cracked in 18 months of mostly street driving & easy forest trails/over-landing. The Thorley headers had a warranty, but they weren't making them anymore, so they offered a credit (if I remember correctly). The fact that they cracked relatively quickly was frustrating! So I bought a set of Banks TorqueTube headers thinking that was the solution, and they cracked in about 18 months too. After that, I put the factory cast iron exhaust manifolds back on. I sold the LJ a couple years after and fixed up a 4 dr XJ for the family.

My thoughts from my experience:
-The headers (both brands), Magnaflow cats, 2.5" exhaust, CAI & 62mm TB definitely increased seat-of-the-pants power from ~3000-5500 RPMs.
-The motor had a "warbling" tone above 3500 RPMs that was distinct with the headers, and sounded unique compared to any other headers on 4.0L.
-The late model 4.0L factory exhaust manifolds are much more durable than the headers I tried; they lasted for years. They are also restrictive in the higher RPM ranges, but the other 'breathing' mods still helped the engine perform better than stock as far as seat-of-the-pants feels. I wish I would have chassis dyno'd it...

If I had a late model 4.0L , I'd consider gasket matching a set of factory exhaust manifolds and adding high flow cats. If you're building a stroker, I'd get a 1991-98 header (I like the Banks Revolver) and have an extra O2 sensor bung welded in. My experience with the late model 3-to-2 headers was not good.