RCP Phx
NAXJA Forum User
- Location
- Phoenix,Az
Can you fit a 3" full exhaust on a factory equipped(design) XJ? I just did a 2-1/2" exhaust but I think it's kind of restrictive.
I agree with you the 2.5 inch exhaust is probably restrictive on you 4.6. V8 4.6 motors run dual 2.5 inch pipes. The only thing I can say about running a 3 inch pipe is that it is much more difficult to fit in spaces where smaller pipes go easily. I've put 3 inch pipes on a couple of cars where I thought it would be no problem and had some clearance issues where I had none with 2.5 inch. I see you put stock muffler and cat back on and I think changing your muffler and cat to high flow units would do everything you need without going to 3 inch.
That's the original question. will it fit! As for a "free" flowing exhaust, I don't want any noise above stock!!!
Can you fit a 3" full exhaust on a factory equipped(design) XJ? I just did a 2-1/2" exhaust but I think it's kind of restrictive.
If you're worried about restriction, here are a couple of things to try:
- Change the catalytic converter for a unit that is spec'd for single-unit application for a large V8 engine (can typically be found in 1980's Chevvy van applications, with the right size inlet & outlet.)
- Change the muffler for a less restrictive unit - spec'd as above, or a low-end performance unit (I like using Walker Turbo II mufflers)
- There is a slight crimp in the downpipe after the exhaust collector, in most cases (I'm sure it's there on RENIX - 1987-1990 - I think it's there 1991-up...) this may be cut out and replaced with a flex joint - which is a good idea anyhow, as the XJ exhaust system is overly rigid, and this is what contributes to manifold cracks (vibrations and stresses get transferred up the plumbing into the weldments and the HAZ of the weldments, and they fail first.)
But, installing a 2.5" exhaust is fine for a stock 4.0L engine, up through a mild (through 4.5-4.6L, IIRC) stroker build. Then, go with a 2.75" setup, and 1.75" primaries.
Have you read the 4643 Jeepspeed thread?
I do not recall them using 3" pipe.
Do not know of anyone that has a stroker using it either.
Only way to know for sure if you need to go larger would be dyno run/tuning, etc.