Putting FUN and FRIENDLINESS, FIRST into owning and learning about AMC small bodied cars, primarily Eagles, Spirits and Concords as well as vehicles built in AMC's Mexican subsidiary, VAM.

  The AMC Eaglepedia can now be accessed using the buttons found below  This is a comprehensive ever growing archive of information, tips, diagrams, manuals, etc. for the AMC Eagle and other small bodied AMC cars. 

Also a button is now available for our Face Book Group page.

Welcome to the AMC Eagles Den.  A new site under "old" management -- so welcome to your new home for everything related to AMC Eagles, Spirits and Concords along with opportunities to interact with other AMC'ers.  This site will soon be evolving to look different than it has and we will be incorporating new features we hope you will find useful, entertaining and expand your AMC horizons.  And, if you were you banned at another AMC Eagle Forum and cannot log in here?  Let us know and we will fix it for you. 

You can now promote your topics at your favorite social media site by clicking on the appropriate icon (top upper right of the page) while viewing the topic you wish to promote.

  • January 16, 2019, 11:29:26 AM

Login with username, password and session length

Author Topic: 4.3 gm engine into Into an Iron Duke with TorqueFlite a904  (Read 3274 times)

0 Members and 1 Guest are viewing this topic.


  • Guest
4.3 gm engine into Into an Iron Duke with TorqueFlite a904
« on: October 08, 2013, 11:45:14 AM »
I'm surprised there isn't more postings on this.

I have an 82 SX4 with a 2.5 Iron Duke (SBC) into a Torqueflite a904 automatic transmission.

1) Since the SBC pattern is the same what is it going to take to upgrade to a 4.3 Vortec or 4.3 TBI?
2) Which engine should I go for a TBI or the newer Vortec? 
3) Will The Torqueflite a904 handle the 190 HP upgrade?

Cheers Mates.

Offline IowaEagle

  • AMC Eagle Archivist
  • Administrator
  • AMC Eagles Den Addicted
  • ******
  • Posts: 31979
  • Thumbs Up 472
Re: 4.3 gm engine into Into an Iron Duke with TorqueFlite a904
« Reply #1 on: October 08, 2013, 12:56:34 PM »
The least I could do was give you a Thumbs Up because you didn't have any.  904's in good working order will handle that much HP, they are used on the strip by some.  Other than that I don't know diddly squat about GM stuff.
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 eaglefreek

  • Moderators
  • AMC Eagles Den Addicted
  • *****
  • Posts: 3987
  • Thumbs Up 206
Re: 4.3 gm engine into Into an Iron Duke with TorqueFlite a904
« Reply #2 on: October 08, 2013, 02:43:25 PM »
I haven't seen any documented swaps that replaced the Iron Duke and retained the 904. I too am surprised there aren't more. You will have to figure out engine mounts and oil pan. Don't the front axles bolt to the transmission bellhousing via a bracket on the 4 cyl. models? If so, no need to worry about axle mounts. I remember someone saying that a dealer in Alaska installed a Chevy 350 in a new Eagle back in the day but didn't have any details.
1986 AMC Eagle Wagon 4.2L/4.0L head, AW4,NP242, Chrysler 8.25" rear.
1981 AMC Eagle Wagon As Seen On TV  Lost In Transmission


"I know he'd be a poorer man, if he never saw an eagle fly,
Rocky mountain high"  John Denver
Click for Fayetteville,TN Forecast" border="0" height="100" width="150


  • Guest
Re: 4.3 gm engine into Into an Iron Duke with TorqueFlite a904
« Reply #3 on: October 08, 2013, 03:40:46 PM »
@IowaEagle Thanks for the thumbs up. I'm a newbie to this forum.  Not a newbie to AMC however.
I have my Mom's 71 Javelin AMX. I was in agreement that the A904 is a very solid transmission. I was just
looking for reaffirmation.


Yeah.  It seems like putting in any Small Block Chevy, would be fairly easy,  if retaining the Automatic transmission. 
IF it isn't broke why fix it? kind of idea.  the v6 4.3 is essentially the 350 just missing 2 cylinders and a balanced
crank.  It seems like every body is going with the 4.0 Jeep engine.  but I feel if I already have the SBC pattern
why not just dump a 4.3 GM in there.  I was hoping somebody was going to tell me, "Yeah, I did it. 100% easy, everything fits
perfectly spacing wise, and the motor mounts are a direct fit." 

I'm pretty heck bent on doing this, so at a Minimum I'll document the entire process for other folk. 

Cheers Mates

Offline carnuck

  • Having a 727 means never re-doing the trans again
  • AMC Eagles Den Addicted
  • ********
  • Posts: 3449
  • Thumbs Up 89
  • Near Seattle
    • Virtual Jeep
Re: 4.3 gm engine into Into an Iron Duke with TorqueFlite a904
« Reply #4 on: October 09, 2013, 01:42:11 PM »
The 4 cyl 904 needs beefing up to go behind a 4.3L if you plan to romp on it even slightly as it's barely strong enough for the TBI 2.5L. First, a wider rear band (sadly there isn't enough room for one from a 999), then a torque converter with an upgraded neck, then a bolt in rear sprague clutch. Extra clutches in the drums help too. It's too bad there weren't any 727s with GM pattern made.
AMC/Jeep gauges are for amusement only. Any correlation between them and reality is purely coincidental!

Offline vangremlin

  • Administrator
  • AMC Eagles Den Addicted
  • ******
  • Posts: 3774
  • Thumbs Up 185
Re: 4.3 gm engine into Into an Iron Duke with TorqueFlite a904
« Reply #5 on: October 23, 2013, 12:55:12 AM »
Good luck!  This sounds like an interesting swap.  I've been reading up on putting the 4.3 TBI on the AMC 258, and this takes it one step further for the 4 cyl guys.
1981 Kammback 258 - "Pepe"
1980 Coupe 258 - "Ginger
1972 Gremlin X 304
1978 Gremlin 4 cyl 121 - sold
1964 TBird 390 - sold


SMF spam blocked by CleanTalk