Author Topic: exhaust for 258  (Read 3678 times)

0 Members and 1 Guest are viewing this topic.

Offline kalve

  • Eagle
  • **
  • Posts: 95
  • Thumbs Up 5
exhaust for 258
« on: November 17, 2012, 11:32:08 PM »
I am needing to replace the whole exhaust system on my 85 Eagle wagon. Was wanting to know what headers an performance cats an mufflers would be good to use on here? An what size exhaust I am planning to do 4.0 head swap etc.. come spring. Should I go with a 2.25 or 2.5 exhaust? I am thinking bout going with the 2.50 exhaust size.
64 T bird landau
70 Cougar Convertible Hurst 4 speed
74 F250 Crewcab shortbed
85 Eagle Wagon 4wd

Offline DaemonForce

  • Grease Magnet
  • Eagle Sport
  • ****
  • Posts: 442
  • Thumbs Up 8
Re: exhaust for 258
« Reply #1 on: November 18, 2012, 04:43:09 AM »
258 block, 242 head, I would use the stock 1991 exhaust header that came off of the engine I pulled the head from. At least that tells me it should work. As for the 258 head, classic stock manifold replacement should be the only major investment you make in that area. The rest is a mishmash of aftermarket internals. Since a lot has changed in 30 years, I think it's worth it. I'm always too far stuck in a bad place to ever actually do the rebuild though and I'll probably never get the chance to find out at this rate. Good luck. :/
1983 Limited
AMC 258C {R2:11.Oct.12}
Carter 2681 {R2:28.Oct.12}
TorqueFlite A998 {R6: -20.Apr.12}
NP129 {R2:28.Apr.12}
M35-273 {???}
Compression: 10.5:1
Corrected Idle: 500RPM

Offline BenM

  • Eagle Turbo Diesel
  • *******
  • Posts: 1379
  • Thumbs Up 66
  • Pittsburgh, PA
Re: exhaust for 258
« Reply #2 on: November 18, 2012, 06:38:29 PM »
The stock 4.0 tubular headers are pretty good. Somewhere here is a writeup about gusseting some connections to prevent it from cracking, and you have to do some turns around the front diff and build a new bracket, but that's not difficult or complicated stuff.

If you have a good exhaust guy, or can spend some time welding pieces yourself, I'd go 2.5 from the manifold back to the cat and muffler, then go down to 2.25 from there on out to save a few dollars. You could even order stock pieces from NAPA for the back and make life easy. You'll never notice the neck down after the muffler, and probably not even if you did it between the cat and muffler.

1987 AMC Eagle Sedan -- 1976 Pacer Coupe -- 1968 Pontiac Tempest Custom S -- 1940 Mercury (& a 2002 Jetta Turbodiesel, 5 spd., the Wife's Daily Driver)

Offline kalve

  • Eagle
  • **
  • Posts: 95
  • Thumbs Up 5
Re: exhaust for 258
« Reply #3 on: November 22, 2012, 08:04:32 PM »
ok I plan to do the exhaust on monday an get he car to pass inspection an be on the road the exhaust shop also does inspections so I will have them do it them an get it legal.
My plans for the car:

full exhaust (already purchased magnaflow universal High performance Cat) looking to go 2.25 or 2.5 on exhaust

add headers

go with 4.0 heads ported an polished

go with Weber or Motorcraft carb

add turbo

switch rear end to Dana 44 maybe limited slip an go probably 3.0 gear

switch trans from auto to 5 speed manual

check bout removing emissions an computer depending on tests in WV rather it will pass inspection.

add skid plate protection

going to do exhaust come monday an the rest of it will be done over time. But based on all this should I go 2.25 or 2.5 exhaust on it
64 T bird landau
70 Cougar Convertible Hurst 4 speed
74 F250 Crewcab shortbed
85 Eagle Wagon 4wd

Offline kajsdf

  • Eagle DL
  • ***
  • Posts: 168
  • Thumbs Up 8
Re: exhaust for 258
« Reply #4 on: December 05, 2012, 12:50:51 AM »
clifford performance makes great headers; i am using the set they designed for the eagle 258 (jeep headers sometimes have fitment issues) and they are really awesome.  i recently built a 258 by their specs and i'm impressed so far.  their products are pricy but worth it if you are looking for performance
1985 eagle wagon limited
now more limited...
2150 swap...tf727/np229 swap...258 megabuild in the works...

Offline jim

  • AMC Eagle Nest Addicted
  • ********
  • Posts: 6492
  • Thumbs Up 101
Re: exhaust for 258
« Reply #5 on: December 05, 2012, 01:13:15 PM »
Did you pass inspection and get it on the road?
I'm right 98% of the time, and I don't care about the other 3%.
"The constitutions of most of our States assert that all power is inherent in the people;
that... it is their right and duty to be at all times armed."
--Thomas Jefferson to John Cartwright, 1824. ME 16:45
What part of "shall not be infringed" do they not understand?
08 Impala
01 Yukon 4X4
(There's more to life than fuel mileage)
83 Eagle wagon; shared responsibility as daily driver
88 Eagle white woody wagon; shared responsibility as daily driver
86 wagon parts car
Click for Little Rock, AR Forecast" border="0" height="100" width="150

Offline TheWraith

  • Eagle
  • **
  • Posts: 133
  • Thumbs Up 7
Re: exhaust for 258
« Reply #6 on: December 06, 2012, 07:29:37 AM »
...well, as well as a 5.5 cyl 4.2 motor can run...)

Now that's funny right there.   ;D

Offline carnuck

  • AMC Eagle Nest Addicted
  • ********
  • Posts: 1747
  • Thumbs Up 55
  • Near Seattle
    • Virtual Jeep
Re: exhaust for 258
« Reply #7 on: December 16, 2012, 01:01:05 AM »
Nice thing about rolling emission cutoffs here in WA. Mine is cleaner than OEM emissions anyways (NOx may be a little elevated) but I hoe to test fit my Jeep header (for HO) for clearance from the block and driveshaft in the near future. I have to complete my MJ so it can be driven and up for sale in the meantime.
'87 Comanche 4.0L AW4/NP242 3.73 gears, lifted 5" on near new 33" tires $3500 obo
'82 Eagle Wagon (Brown Betty) 4.2L/727/NP229 and soon 8.25 rear axle and non-vacuum 3.08 front to match. 235/75/15 tires. It's down to minor body work (someone creamed my driver's door but I have another in good shape) almost rust free and interior work (seats are worn and carpet torn). $2000 but about to go up due to more work being done.

Pics of my other for sale stuff


1980 intake manifold 1985 exhaust manifold???

Started by 85AmCfreak

Replies: 9
Views: 3185
Last post March 20, 2012, 10:20:45 AM
by BenM
Temporary or Permanent Exhaust Repair?

Started by OverKnight

Replies: 20
Views: 7064
Last post June 15, 2012, 02:35:03 AM
by carnuck
Clifford Dual exhaust headers 6=8

Started by olymunch

Replies: 25
Views: 7664
Last post May 30, 2012, 05:12:42 PM
by olymunch
Missing exhaust , need help with parts & location

Started by kral

Replies: 9
Views: 3771
Last post May 26, 2011, 10:31:46 PM
by kral
exhaust backfire and popping sounds

Started by pradtf

Replies: 5
Views: 2208
Last post May 25, 2011, 05:34:06 PM
by AMCKen