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Unread 04-07-2012, 07:28 PM   #1
7ate9
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head swap or stroker... what's the big difference!?

Okay, maybe I'm being a numbskull and totally overlooking something. But, is there really that much of a difference between putting the 4.0 head on a 258 and putting the 258 crank and rods into a 4.0? I realize the 4.0 has a slightly larger bore so you'd end up with a few more cubes going the stroker route. Other than that though, both setups will give you the longer stroke of the 258 combined with the better flow of the 4.0 top end. So, if someone could fill me in on what I'm missing my curiosity would really appreciate it..

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Unread 04-07-2012, 07:35 PM   #2
AKGeo
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that increased bore makes a big difference, as do the larger valves on the 4.0 head.
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Unread 04-07-2012, 08:11 PM   #3
7ate9
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Does it really though? unless I'm mistaken, the stroker only ends up with less than 20 more cubic inches than than a 258. Now, I'm a firm believer that there is no replacement for displacement and I understand that 20 cubic inches would make a difference, I just don't see it being so significant or noticeable that it would make it worth doing a complete engine swap over just a head swap in an older jeep with a 258 already in place. Especially for someone who would keep it carbureted and need to worry about a fuel pump. I was wondering if there was some other benefit to the 4.0 block being used or if it's just the larger bore?
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Unread 04-08-2012, 06:05 PM   #4
AKGeo
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I'm sure there's a reason that a 4.7 stroker (30 Cu.In more than your 258, btw) makes on average 75hp/100 lbft more than any stock i6 found in a Jeep. Perhaps it's the added fuel from the injectors (required) and added air from the higher flow head.
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Unread 04-08-2012, 07:39 PM   #5
7ate9
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okay, but the stroker is only a 4.5 liter until you bore it 60 thousandths over to make it a 4.7.. You can also bore a 258 to get a little more displacement. So I'll stand by my assumption of roughly only a 20 cubic inch difference. I also never said anything about a stock engine, I was comparing a typical stroker build to a 4.0 head being put on the 258. So either of the engine builds I mentioned would end up with the same head, which would mean the same amount of flow on both engines.. I also don't see fuel injection delivering more fuel than a carb (Not that it's even relevant to my question) Nor do I get what you mean by injectors being required, seems how I have a newer horseshoe style 4.0 intake with a motorcraft 2150 on it and the injector ports blocked off..
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