4.0 head swap - JeepForum.com

 
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post #1 of 9 Old 10-18-2004, 06:37 PM Thread Starter
MillerHalrey76
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4.0 head swap

what kind of gains am i lookin to get off my cj 4.2 with the 4.0 head swap? how much total am i lookin at paying? is it worth it or no is what im trying to figure out. thanks for the help guys


98 cherokee


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post #2 of 9 Old 10-18-2004, 09:01 PM
Jeep Daddy
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Quote:
Originally Posted by MillerHalrey76
what kind of gains am i lookin to get off my cj 4.2 with the 4.0 head swap? how much total am i lookin at paying? is it worth it or no is what im trying to figure out. thanks for the help guys
I was wondering if doing the 4.0 head swap and keeping it carburated is going to net some gain as well...

2004 Rubicon, 6" lift, 35s, winch, hard top, full doors, bumpers, tire carrier and rock sliders.
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post #3 of 9 Old 10-19-2004, 03:51 AM
Greezy Gringo
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This has been discused about a billion times. Do a search for it.
Or read this write up:
http://monsterslayer.com/jeep/40Head/40Head.htm

I just put a new motor, with warranty, in my 80 CJ7. Im going to do the head swap once the warranty runs out. Everything Ive read says you get like ~40 HP and lotsa torque from the upgrade. Ive been watching a head on eBay that was designed for the swap. http://cgi.ebay.com/ebaymotors/ws/eB...category=33617

Keep in mind that you'll need new intake manifold...

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post #4 of 9 Old 10-19-2004, 01:16 PM
gosupes
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Quote:
I was wondering if doing the 4.0 head swap and keeping it carburated is going to net some gain as well...
Yes it does, a large gain. FI is still the better way, but a carb is a low buck, low tech way to get started.

Quote:
Keep in mind that you'll need new intake manifold...
I have heard that the old intake can be used with some grinding. A new exhaust manifold is a must. The eBay head is a bit expensive but if you have more money than time, still a good option. Look for the 7120 head, better flowing than the others.

Overall this is a good cost to power ratio mod.

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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post #5 of 9 Old 10-19-2004, 03:06 PM
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http://www.cjoffroad.com has a whole forum dedicated to this swap. Tons of info there that I haven't seen other places. From what I have read, it is completely worth it.

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post #6 of 9 Old 10-19-2004, 04:46 PM
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Quote:
Originally Posted by gosupes
Look for the 7120 head, better flowing than the others.

Overall this is a good cost to power ratio mod.
What is a 7120 head off of???? How can you tell the difference???

2004 Rubicon, 6" lift, 35s, winch, hard top, full doors, bumpers, tire carrier and rock sliders.
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post #7 of 9 Old 10-20-2004, 07:47 AM
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I'm not 100% sure of all of the casting numbers, but I would not do the swap with a pre-HO head, that's the big difference. Someone check me, but I think it was like 92 or 94 when the HOs came on line.

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post #8 of 9 Old 10-21-2004, 12:13 AM
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92-94 sounds right to me.

I'll be doing this upgrade around this time next year (when the warranty expires on my new motor.) I was looking at upgrading the cam too. Anyone with cam experience? It's a DD when the weather is nice. Soo like a good low-mid range torque boost?

'87 Grand Wagoneer
'80 CJ7
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post #9 of 9 Old 10-21-2004, 06:25 AM
gosupes
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Quote:
Originally Posted by Greezy Gringo
Anyone with cam experience? It's a DD when the weather is nice. Soo like a good low-mid range torque boost?
I run a 260* cam which has a low torque curve, not a DD but it has been seeing a lot of miles lately. A 264* would be good also.



Quote:
What is a 7120 head off of???? How can you tell the difference???
Yeah, the 7120 is the casting from the 92-94HO engines, they flow better than other HO engines. But any HO head is still better than the stock head.

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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