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Unread 03-21-2006, 09:37 PM   #1
80cj5
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Join Date: Mar 2004
Location: Green Bay wisconsin
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258 .60 4.0 head

pulled my engine and sent it to the machine shop boring it out .60 over and putting a 4.0 head on, with a 4 brl carb any one know the power gain about from what im doing?? i know the head swap alone is around 40 or so from what ive read on other sites from people doing it

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1989 yj 4.2L, 3" rough country lift, 2" body, 1.5" shackle lift, sye, 35x12.5 cooper discovery stt's, costom rear bumper with d ring mounts, 4 brl holley 390cfm, offenhouser 4brl intake manifold, hollowed out cat, dynomax straight through muffler, t-case out of a ram, 4.11 gears, super dana 35 kit with detroit
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Unread 03-21-2006, 11:06 PM   #2
gosupes
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1986 CJ7 
 
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I have never heard of any actual numbers from a dyno, just seat of the pants impression. There are other factors like exhaust, cam, etc, so everyone will be a bit different.
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1986 CJ7, 4.2 w/4.0 head, TFI-HEI hybrid ignition, Clifford manifold w/Holley 390 w/cold air intake, OBA, 4.5" lift, Woody CV shaft and Tattons in front, 4.10 gears - lunchbox in front, Truetrac in the back, twin-sticked, blower upgrade for running topless, trying to keep it simple.

It's just a Jeep, and if you don't wheel it once in a while, it's not even that.
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Unread 03-22-2006, 11:35 AM   #3
gumcrew2
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If you don't do any other mods (cam, intake, exaust) probably 200ish. But it'll be WAY torqueier. When you accelerate from a stop it'll haul.
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Unread 03-22-2006, 12:46 PM   #4
XJ4oh
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1997 XJ Cherokee 
 
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Check out Clifford Performance's website, they offer some insight on the swap... tehy sell the whole kit I think.
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Unread 03-22-2006, 03:16 PM   #5
Gper4life
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I had a 4.0 head on my 258 with the 390 holley and offenhouser intake and let me tell you that puppy would break the 35's loose with ease. Out ran my wifes new Liberty until my gear ran out(4.10). Boring it out will only increase the power. You may even want to look into a HEI distributor from about a 72 chevy van with the 250 six cylinder. Only thing is you have to put a v8 drive gear on it from an amc v8. That helped me out by opening up the gap on the plugs. You may even be able to up the carb size to the newer 470 cfm truck avenger.
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