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258 w/ 4.0 head, or 4.0 engine swap?

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zeidrach View Drop Down
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    Posted: Nov/21/2009 at 6:51am
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Nov/21/2009 at 7:02pm
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.
Chris

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zeidrach View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeidrach Quote  Post ReplyReply Direct Link To This Post Posted: Nov/21/2009 at 7:49pm
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 7:50pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Nov/21/2009 at 8:15pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rodger Quote  Post ReplyReply Direct Link To This Post Posted: Nov/21/2009 at 11:13pm
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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Post Options Post Options   Thanks (0) Thanks(0)   Quote zeidrach Quote  Post ReplyReply Direct Link To This Post Posted: Nov/21/2009 at 11:28pm
Originally posted by Rodger Rodger wrote:

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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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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rodger Quote  Post ReplyReply Direct Link To This Post Posted: Nov/21/2009 at 11:42pm
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" .
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Nov/21/2009 at 11:46pm
Originally posted by Rodger Rodger wrote:

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" .
 
 
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Ive seen older 232's have 2BBL's  and the motorcraft swap is very common.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Greyhounds_AMX Quote  Post ReplyReply Direct Link To This Post Posted: Nov/22/2009 at 10:18am
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.
Chris

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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Nov/22/2009 at 5:24pm
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.
Frank Swygert
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