4.0 Head Swap on 4.2L 258 - Page 3 - JeepForum.com

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post #31 of 68 Old 05-01-2011, 04:25 PM Thread Starter
WillyC24
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Nearing the end of the work on the 4.0L head conversion and full 4.2 rebuild, and now have a few questions on the valve cover breather vs. PCV valve configuration.

My engine shop says the manual calls for two breathers, while I normally see a PCV valve on the front. Any advice here? I've attached a picture of my engine (you'll see the two breathers installed):



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post #32 of 68 Old 05-02-2011, 01:01 AM
gosupes
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Get them from the stealership. One is restricted flow, goes from vacuum source to cover. The other is just a basic elbow, goes from the cover to a filtered air source like the air cleaner assy.

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 #33 of 68 Old 05-02-2011, 06:12 AM
razor2264
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Quote:
Originally Posted by WillyC24
Nearing the end of the work on the 4.0L head conversion and full 4.2 rebuild, and now have a few questions on the valve cover breather vs. PCV valve configuration.

My engine shop says the manual calls for two breathers, while I normally see a PCV valve on the front. Any advice here? I've attached a picture of my engine (you'll see the two breathers installed):
Hey Willy,

I'm using the Clifford set up similar to yours. I have a question regarding the weber 38 with that setup. What idle jets did you end up using? Also did you have any problems with coolant leaking inside your Clifford intake? Mine has a slow leak, but it still runs. Might want to take the carb off and check. Currently there is a month long wait for the replacement.
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post #34 of 68 Old 05-02-2011, 11:28 AM Thread Starter
WillyC24
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Thanks, Razor. I'll check into that.

Gosupes - in summary, you're saying no PCV valve. Does the true breather go on the rear hole, and the elbow on the front?
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post #35 of 68 Old 05-02-2011, 12:51 PM
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Quote:
Originally Posted by WillyC24 View Post
Thanks, Razor. I'll check into that.

Gosupes - in summary, you're saying no PCV valve. Does the true breather go on the rear hole, and the elbow on the front?
Do you know which idle jets you are using with your setup?

Thanks!
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post #36 of 68 Old 05-06-2011, 11:34 AM Thread Starter
WillyC24
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Razor - sorry, I don't know what jets I'm using, other than I bought the Redline Weber 38/38, which is supposed to have been fitted with the proper jets before shipment.

Also, further confusion on the PCV vs. breather conversation -- my instructions from Clifford on the Weber carb say NOT to use a PCV and to use breathers on both holes. Yet still, everywhere else I read that I should use a PCV.

In other news, I had my rebuild dyno'd and she's topping out at 200HP and 237 lb-ft of torque. See the full PDF report here.
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post #37 of 68 Old 07-04-2011, 11:26 PM
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Quote:
Originally Posted by WillyC24 View Post
In other news, I had my rebuild dyno'd and she's topping out at 200HP and 237 lb-ft of torque. See the full PDF report here.
I found this thread while searching Google for 4.0 head articles, it caught my eye because I know a lot of people have asked about *real* hp and tq numbers following the 4.0 head swap. I have had visions of a 4.0 head, Offy intake and Borla header even though I have never fired up my engine...it is truly a disease

WillyC24

Do you have the engine back in the CJ?

What cam and exhaust did you use?

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post #38 of 68 Old 07-06-2011, 12:20 PM
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WillyC24 was on line in early June, hopefully he will jump back in to provide an update.

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post #39 of 68 Old 07-06-2011, 01:05 PM
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Originally Posted by foggybottombob View Post
I got one from clearwater also but I will say that I could not tell any difference in seat of the pants power difference. I got a very noticeable power increase from putting in the HEI distributor.
I read about similar results on another thread a while ago. Makes me wonder. I was on the verge of doing a head swap but decided to hold off. A lot of times people do other upgrades when they do a 4.0 head swap so it makes me wonder where the performance increase claims actually come from. I still run a stock 258 and like you, noticed a nice increase in throttle response when I installed a DUI dizzy.
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post #40 of 68 Old 07-06-2011, 09:22 PM
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Quote:
Originally Posted by WillyC24 View Post
Thanks, Razor. I'll check into that.

Gosupes - in summary, you're saying no PCV valve. Does the true breather go on the rear hole, and the elbow on the front?
Doesn't matter, they are both basically the same but one is restricted. I think I have the restricted one in the front, the hose routing work better for me that way.

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 #41 of 68 Old 07-07-2011, 08:43 AM
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Maybe I'm the only one on the planet that had this issue, here goes. I installed the Felpro head gasket that the machine shop provided me. When I first fired it up, I filled my oil pan with $20 worth of antifreeze. Upon removal I noticed (after not before) that the new gasket had an overlap between the water and oil passage. I bought a new gasket and all was well. I know the original 258 head gasket did not have this but the one in the gasket set did. I don't remember if the gasket was a 258 or 4.0. Moral of the story check your head gasket.

1985 CJ7 - total customization underway, Sublime green and Plum crazy purple, Ford 9", 258 w/ Holley 475
1985,93 CJ7,YJ - L98 TPI Vette motor, Atlas twin stick, Dana 60s front and rear, Arbs, 39.5 Swampers
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post #42 of 68 Old 07-07-2011, 10:00 AM
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For some of the pricing I seen in this thread, You could easily do a 4.6 low buck stroker and end up in the 250 hp & 300+ tq range
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post #43 of 68 Old 07-10-2011, 09:22 AM Thread Starter
WillyC24
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Howdy all, sorry for the delay - I've been on the road a bit. I have the engine on the frame now, but the CJ still looks like a moon rover. So, no "real world" tests yet. I'll update as soon as possible!
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post #44 of 68 Old 07-27-2011, 09:23 AM
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Newbie here and I have to say this is the best conversation I've found on the topic. Lots of great information from ya'll.

I just bought a friends jeep (87YJ) and he was getting ready to perform this mod. I didn't want to rush into it, but the engine was smoking so bad that I just went ahead and dove right in. I have the old head off and I'm glad I went ahead with the mod as there was coolant in the 4th and mild rust between between 3,4, and 5th cylinders and while the valve train didn't look bad I suspect the seals were leaking pretty bad too.

But anyway, can anyone tell me if there is a way to identify which 4.0L head I have? I can't ask my friend b/c he's in Afghanistan.
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post #45 of 68 Old 07-27-2011, 11:10 AM
foggybottombob
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There is a number cast into the surface of the head. The 91-95 heads were 7120. That is what I used.
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