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258 w/ 4.0 head, or 4.0 engine swap? |
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zeidrach
AMC Apprentice Joined: Jul/20/2009 Location: Chico,ca Status: Offline Points: 103 |
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Posted: Nov/21/2009 at 5:51am |
I have a 1972 AMC Hornet, with the 258 and a 904 chrysler transmission. I've been looking online for the past few hours into the 4.0 head swap. Looks fairly easy, I could either seal off the ports with JB weld or have them welded and the head resurfaced at my local Riebes.
Which will gain me more horsepower, a 4.0 head on a 258, or a whole 4.0? Either way the engine will be carbed, and I'll probably run the stock 4.0 header. I'm on a budget, so no fancy headers for me. There's plenty of 4.0's at my local pick and pull, and 1 258 in an 84 Eagle I could use if need be.
Should I use the aluminum 2bbl Eagle intake I have laying around here, with a motorcraft 2100(already own as well), or order the Clifford performance intake with either the 2 or 4 bbl adapter plate?
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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From a displacement standpoint, the 258 wins, but if you're going to run a stock cam the 4.0L cam is going to be more agressive. Of course it doesn't have a fuel pump cam though so you'd need an electric fuel pump.
I think you're on the right track for a low buck and fun engine project.
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1968 AMX 390 w/T5
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zeidrach
AMC Apprentice Joined: Jul/20/2009 Location: Chico,ca Status: Offline Points: 103 |
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I'm leaning more towards the head swap, I can get one for cheap at pick and pull, plus I won't have to pull my engine. I could probably do it, but I don't have a hoist, soo...
If I go with the head swap, what intake should I use? Can I use the stock 4.0 intake and buy a carb adapter? Should I keep my eyes out for an Offy 4bbl intake on the cheap? Right now, I'm in the middle of putting the original 1bbl intake on till I can afford the swap. I'm painting it the engine, the paint is drying as I type right now. Also, I was thinking of buying a mild cam, can what would you guys recommend($50-$250 range)? Edited by zeidrach - Nov/21/2009 at 6:50pm |
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16591 |
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IMO, bore and stroke in 4.0 is much better. but if you dont have the $$, well, then stick with the 258.
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Rodger
AMC Apprentice Joined: Aug/22/2008 Location: Colo Spgs Status: Offline Points: 53 |
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Sir
I like the 2 bbl option. Carb's are every where
and Stock Appearing 2 bbl Air Cleaner Housings
are more attactive when you open the hood
at a event that has other AMC Driver's around.
There is a pride in saying, " ... oh its just an
AMC Straight Six".
Rodger & Gabby
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Rodger & Gabby
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zeidrach
AMC Apprentice Joined: Jul/20/2009 Location: Chico,ca Status: Offline Points: 103 |
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Which 2bbl do you mean, a motorcraft, or a stock one from an eagle? I have a motorcraft 2bbl around here, I had on the 258, but ran like poo. |
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Rodger
AMC Apprentice Joined: Aug/22/2008 Location: Colo Spgs Status: Offline Points: 53 |
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Sir
AMC started using a 2 bbl Air Cleaner Housing, Carb and intake about 1972 on the 258's. The six banger carb is better matched with CFM's to the cubes than something from a V8 and be drowning from being "over-carb'd" .
Rodger & Gabby
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Rodger & Gabby
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purple72Gremlin
AMC Addicted Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16591 |
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Greyhounds_AMX
AMC Addicted Joined: Nov/14/2009 Location: Kansas City Status: Offline Points: 1268 |
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I think the later model aluminum intake with a Weber carb would be a good combo coupled with the 4.0L head and 4.0L factory header.
Add a hotter cam and you should be cookin'. The 4.0L head with bring your compression up as well, so you may need ot be selective on the cam. I've run the Crane HMV272 alot and like it alot, but a little higher stall converter would be nice with it. There are probably better choices for this combo.
If you make a cam change you'll need valve springs and retainers as well, though.
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1968 AMX 390 w/T5
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farna
Supporter of TheAMCForum Moderator Lost Dealership Project Joined: Jul/08/2007 Location: South Carolina Status: Offline Points: 19612 |
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With a carb you're better off with the 258 and 4.0L head. As Chris mentioned, you'll get a little compression boost too. If you had to build a block I'd say use the 258 crank and rods in the 4.0L block with 4.0L stock pistons. That gives a bigger compression boost due to the longer stroke, and makes a 280 inch engine.
Some Jeep racers have been running carbs on the 4.0L intake. I don't know if they are buying or making adapters, and I don't know what carb -- I think it's a "souped up" 1V. That would certainly be the easiest to adapt! I'd use a 1981-90 258 2V intake. You almost have to have one of those with the 4.0L head. you can run a Carter BBD 2V (pre smog!!) or a Motorcraft 2150 or better yet a Holley 2300. You need the small Motorcraft or Holley though. There were 350 and 500 cfm versions. The small Motorcraft will have "1.08" stamped in a circle somewhere on it. It was used on 289/302 Fords and 304 Jeeps. Can't tell you how to ID the Holley. Jets are hard to come by for the Ford, the Holley is the primary half of a Holley 4V -- easy to get help on tuning and all parts. |
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Frank Swygert
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