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Author Topic: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke  (Read 32831 times)

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Offline BenM

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The early AMC 4s used a similar ECM to the AMC 6 that AMC called CEC. It was only programmed slightly differently and used a PWM solenoid instead of the stepper motor on the feedback carb. (As per the TSM.) It was a YFA carb, similar to the old YFs used on the old 232s and 258s.

I think all the 151s used a Rochester Varajet either with or without a PWM solenoid and C4 feedback, which is a totally unrelated system. The Varjet used a progressive secondary design like a Weber 32/36 DGEV.
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Offline carnuck

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It's not hard to retrofit
Althought the AMC 4 was not EFI'd in the Eagle. 

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Offline Prafeston

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #17 on: December 04, 2013, 07:37:18 PM »
Cool stuff in here! I'm researching the Iron Duke right now so I found this thread very helpful!
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Offline captspillane

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #18 on: December 05, 2013, 06:17:04 PM »
Good timing in reminding me about this thread Rafe. I have information to post here soon.
Currently Inspected and Insured as of Jan 2013:
-1985 Eagle Station Wagon 258 T5 Stickshift
-1980 Eagle Station Wagon 258 Auto Fuel-injected with GM TBI

Minor Repairs Underway:
-1982 Eagle SX4 258 T5
-1981 Kammback 2.5L Iron Duke T5

Restoration Efforts Near Completion:
-1982 SX4- 401 NV3550
-1983 SX4- 4.5 MPI NSG370 (6 Speed)

Restoration Efforts Underway:
-1985 SW- 4.0 MPI AX15
-1982 SX4- 4.0 AW4
-1981 SX4- SD33T NV4500 (Turbodiesel 5 speed)

Future Rescue Efforts- '85 Maroon SW, '87 Limited SW, '84 Limited SW, '87 4 door Sedan, '81 2 door Sedan, '88 White SW, '77 4 door Hornet, '74 2 door Hornet, '79 Spirit AMX, '81 Kammback.

RIP- Red '81 SX4, '84 4dr Sedan, '84 SW, '81 SW, '80 Spirit, '83 SW, '83 4dr Sedan

Offline Prafeston

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #19 on: December 05, 2013, 06:49:18 PM »
Right on! Sounds like a nice upgrade. More horsepower and better mileage than a stock 4.2 I would think!
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Offline captspillane

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #20 on: December 05, 2013, 11:03:00 PM »
It also solves some major headaches about the crossflow head design. People often comment about how wide open the Eagle Iron Duke engine bay is and assume it must be easy to work on. It's a nightmare! Everything is crammed into one little corner! The engine bay in my Kammback with the non-crossflow head is wide open and everything is accessible the way it should be. That is reason enough for the upgrade.

I posted on the Monza forum a few month's back and someone did have the parts I wanted. It took a long time to close the deal but a box full of Monza parts is on its way this week. I actually own two sets of the rare automotive manifolds from a '77 Monza now. The freshly rebuilt Monza engine will stay in my roadworthy Kammback while I do this upgrade to my second Kammback. In my garage right now I've got two 3.0L and one 2.5L Mercruiser motors and a pair of stock Eagle Iron Duke's for comparison and tear down pictures. It's coming together steadily but slowly.
Currently Inspected and Insured as of Jan 2013:
-1985 Eagle Station Wagon 258 T5 Stickshift
-1980 Eagle Station Wagon 258 Auto Fuel-injected with GM TBI

Minor Repairs Underway:
-1982 Eagle SX4 258 T5
-1981 Kammback 2.5L Iron Duke T5

Restoration Efforts Near Completion:
-1982 SX4- 401 NV3550
-1983 SX4- 4.5 MPI NSG370 (6 Speed)

Restoration Efforts Underway:
-1985 SW- 4.0 MPI AX15
-1982 SX4- 4.0 AW4
-1981 SX4- SD33T NV4500 (Turbodiesel 5 speed)

Future Rescue Efforts- '85 Maroon SW, '87 Limited SW, '84 Limited SW, '87 4 door Sedan, '81 2 door Sedan, '88 White SW, '77 4 door Hornet, '74 2 door Hornet, '79 Spirit AMX, '81 Kammback.

RIP- Red '81 SX4, '84 4dr Sedan, '84 SW, '81 SW, '80 Spirit, '83 SW, '83 4dr Sedan

Offline Prafeston

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #21 on: December 05, 2013, 11:06:52 PM »
Very cool. A buddy of mine has a parts car Monza just sitting at his house. I wonder which engine is in it..
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Offline IowaEagle

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #22 on: December 06, 2013, 08:46:24 AM »
This is an interesting upgrade.   I thought most marine engines were reverse rotation, apparently these are not?
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Offline rollguy

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #23 on: December 06, 2013, 12:10:14 PM »
This is an interesting upgrade.   I thought most marine engines were reverse rotation, apparently these are not?
I believe reverse rotation engines were only needed when 2 engines were used together.  My brother had a friend in Washington that had a commercial fishing boat.  It had 2- Chevy V8 engines, one standard rotation, the other reverse.  The reverse rotation engine had 5 things different- water pump, cam, distributor, starter, and alternator.  When these items went bad, the cost was 3 or 4 times that of it's standard rotation counterpart (marine only).  Everything on the standard rotation engine was normal automotive stuff.
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Offline IowaEagle

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #24 on: December 06, 2013, 12:24:17 PM »
Thanks Rich.  That makes a lot of sense.  Just like GM fuel pumps being cheap for a Chevy, but the same pump was four times the cost when bought for a Allis Chalmers tractor.
Click for Toledo, IA Forecast" border="0" height="100" width="150   


Not a Jeep.  Not a Car.  Its an AMC Eagle!

1982 Eagle SX/4 Sport;
1980 Concord DL;
1970 Ambassador 2 Dr HT, SST
2002 Hyundai Santa Fe;
2008 Jeep Patriot Sport - Freedom Drive II

Offline captspillane

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #25 on: December 07, 2013, 01:16:25 PM »
For the Iron Dukes the biggest difference between marine duty and automotive duty is the distributor. It has a limited range of operation because the propellor dictates a very narrow range of RPM and a steady operating power. The Mercruiser carbs also would not work well in a car because they're not designed for driving in traffic, just steady on. In this case the marine dizzy gets chucked in the trash and an automotive one put back in its place. They are externally identical.

Usually the main reason "marine duty" is so expensive is not for rust control or fire prevention, it is because of the duty cycle. A Marine engine is put under full load and left there the entire time you're using it. In this case with the Merc Iron dukes it only cost a couple dollars more for the corrosive moisture and salt resistant plugs on the side of the motor but it cost over a thousand dollars more from the factory for the "Super Duty" cranks they had.
« Last Edit: December 07, 2013, 01:18:15 PM by captspillane »
Currently Inspected and Insured as of Jan 2013:
-1985 Eagle Station Wagon 258 T5 Stickshift
-1980 Eagle Station Wagon 258 Auto Fuel-injected with GM TBI

Minor Repairs Underway:
-1982 Eagle SX4 258 T5
-1981 Kammback 2.5L Iron Duke T5

Restoration Efforts Near Completion:
-1982 SX4- 401 NV3550
-1983 SX4- 4.5 MPI NSG370 (6 Speed)

Restoration Efforts Underway:
-1985 SW- 4.0 MPI AX15
-1982 SX4- 4.0 AW4
-1981 SX4- SD33T NV4500 (Turbodiesel 5 speed)

Future Rescue Efforts- '85 Maroon SW, '87 Limited SW, '84 Limited SW, '87 4 door Sedan, '81 2 door Sedan, '88 White SW, '77 4 door Hornet, '74 2 door Hornet, '79 Spirit AMX, '81 Kammback.

RIP- Red '81 SX4, '84 4dr Sedan, '84 SW, '81 SW, '80 Spirit, '83 SW, '83 4dr Sedan

Offline carnuck

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Re: Replacing the 80 HP 2.5L Iron Duke with a 140 HP 3.0L Mercruiser Iron Duke
« Reply #26 on: December 11, 2013, 06:21:15 PM »
Later on boat designers got smart and used a transmission to reverse the prop rotation.
AMC/Jeep gauges are for amusement only. Any correlation between them and reality is purely coincidental!

Offline DownwardFlame

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I've been doing a lot of research on the iron duke as I am considering buying a 4 cyl sx4. I have found that the cross flow head is rather poor flowing and tends to crap out at 4500 rpm and has very thin runner walls that only allow for very minimal porting. In the cyl head thread I think I read that the AMC 150 head out performed it. My question is will the 150 head bolt on to the 151 block?
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Offline carnuck

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totally different engines.
AMC/Jeep gauges are for amusement only. Any correlation between them and reality is purely coincidental!

Offline Creepingmonza

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I have a 1980 Chevy monza with a 151 iron Duke and want to swap for the mercruiser 3.0.I'd like detailed info on this swap and it can be sent to creeper0629@gmail.com.my 151 is pushing maby 70-76 hp and brand new was 82.this merc is the same block with a stroker kit and will double my hp without me haveing to mod my while front end,and weight should be the same.it is converted for Marine use so I'll need help converting back to automotive use.

 

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