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  • June 14, 2024, 01:54:15 AM

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Author Topic: 4.2 really that underpowered?  (Read 9133 times)

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Offline mechanic80

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4.2 really that underpowered?
« on: February 03, 2014, 11:27:15 AM »
My 87 Eagle with the straight 6, neutered and with a 2100 Motorcraft carb  (jetting is best selected for this altitude) has little if any reserve power. Ignition advance is per formula taking altitude into account.   Granted, @ 7300' altitude in New Mexico you see few Eagles soaring that high (real or otherwise.)  I've found that letting it warm up for at least 5-8 minutes is necessary for any reasonable stoplight getaway, and it'll do 85 MPH downhill on the freeway!  I guess the question is, does anyone have any tips on squeezing an extra few horses from the engine?   Mileage on the car is about 154000, no smoking and when warm idles great.  MPG varies but being mostly highway,  is between 18-222 depending on weight of right foot.    I primarily use it for heavy snow days and boy, does she love that!   It'd just be great to have a little more "oomph" climbing those hills outside Albuquerque on the way home.  :amc:
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Offline youngkyle

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Re: 4.2 really that underpowered?
« Reply #1 on: February 03, 2014, 11:31:13 AM »
222 MPG? man I wanna get in on that action.  I don't know anything, but I'd be interested in this too.

Offline eaglefreek

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Re: 4.2 really that underpowered?
« Reply #2 on: February 03, 2014, 12:25:54 PM »
Auto transmission? They are pretty anemic. The high axle gearing and a very mild camshaft are probably the major reasons they seem underpowered. My first Eagle, an 81 wagon with a manual 4 speed, seemed a bit quicker than my 86 automatic. Installing a 4.0l head and a different camshaft made a world of difference on my 86. I've also installed 3.08 gearing, but plan to go to 3.55's since I've installed an AW4 transmission.
1986 AMC Eagle Wagon 4.2L/4.0L head, AW4,NP242, Chrysler 8.25" rear.
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Offline IowaEagle

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Re: 4.2 really that underpowered?
« Reply #3 on: February 03, 2014, 08:02:26 PM »
Any smog stuff still active on it?
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Offline mechanic80

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Re: 4.2 really that underpowered?
« Reply #4 on: February 05, 2014, 06:33:01 PM »
Would you believe.....22 point 2?  :amc:  Lets mark that up to fat fingers.  And no, no emission systems are active.  The neutering was very successful .  :amc:  I'd consider the head swap, but as little as I use it, I can deal with an extended warm-up and lackluster power.  BUT IT SURE TACKLES THE SNOW!!!!!!!!!!!!
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Offline carnuck

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Re: 4.2 really that underpowered?
« Reply #5 on: February 11, 2014, 11:22:25 PM »
Sounds like you haven't advanced the timing to account for the higher altitude? Maybe the mechanical advance in the dist is sticking? Vacuum advance blown out? Loose intake to head bolts?
AMC/Jeep gauges are for amusement only. Any correlation between them and reality is purely coincidental!

Offline JayRamb

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Re: 4.2 really that underpowered?
« Reply #6 on: February 13, 2014, 01:15:39 PM »
I tried a lot of stuff with my 87 Eagle to get it more power. Finally changed out the CAT and muffler! WHAT A DIFFERENCE! MUCH faster acceleration and faster passing power.
Jayson H.
Best HWY Mileage of 87 Eagle:  26.2 MPG

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Offline Nightpath

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Re: 4.2 really that underpowered?
« Reply #7 on: March 26, 2015, 06:54:26 AM »
I know this is old, but I found that with the old 258, in Eagles or Jeeps, an upgrade to the ignition system is hands down the easiest and best upgrade to it that can be done.

The 258 was mostly low end torque, and there are ways to get it to perform better.
« Last Edit: April 03, 2015, 10:50:30 AM by Nightpath »


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