5.2/5.9 cracked heads - JeepForum.com
 
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post #1 of 11 Old 10-21-2016, 12:25 AM Thread Starter
Donutjeep12
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5.2/5.9 cracked heads

Hey guy quick question. Im in the process of getting a 5.9 ready for my 94 zj. But the machine shop called and said that the 5.9 heads are both cracked between valves on the outer set of the intake and the exhaust. So i am hoping that when i pull my 5.2 out that my heads aren't cracked and i could use them hopefully. So the question is any of you guys running on cracked heads? Did you have the shop put bigger valves in? Buy reman or aftermarket heads like EQ or eldlebrock? I just dont have the budget for a set of heads. Please let me know what you guys have done. Thank you

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post #2 of 11 Old 10-21-2016, 02:41 AM
Timo_90xj
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5.2/ 5.9 quite often crack theur heads. I've seen numbers as high as over 50% of them having cracked heads at 150-200k miles. They often run ok even with cracked heads, but they are not worth fixing if they are.

Reman heads on rockauto are about 300$ per head, ir you can get better heads with bigger valves at a slightly higher price.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #3 of 11 Old 10-21-2016, 07:01 AM
HighLonesome
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5.9 heads crack more than 5.2 because of the extra heat. Maybe you will get lucky with your 5.2 heads.
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post #4 of 11 Old 10-21-2016, 07:37 AM
jeepjeepster
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Im sure it happens but but yet to have read about those cracks causing an issue...

1994 ZJ-I6 w/216,000 mi
1998 ZJ 5.9 w/65,155 mi Slate Black
2004 KJ w/90,300 mi
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post #5 of 11 Old 10-21-2016, 07:56 AM
Timo_90xj
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Quote:
Originally Posted by jeepjeepster View Post
Im sure it happens but but yet to have read about those cracks causing an issue...
Like I wrote above, a lot of them crack but it usually doesn't cause issues.

But, cracked heads usually aren't worth fixing or modifying.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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post #6 of 11 Old 10-21-2016, 08:35 AM Thread Starter
Donutjeep12
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Thank you guys for the replys. Ill just hope that the 5.2s are not cracked. But if they are ill just save up for some reman ones. To bad they wont take 4 cores lol
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post #7 of 11 Old 10-22-2016, 08:36 PM
Candymancan
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Heard ratmonkey many years ago mention the 5.9 heads crack alot. But it usually doesnt cause issues. Usually... lol
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post #8 of 11 Old 10-22-2016, 09:13 PM
Texas ZJ1
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Neither my 5.2 with 225k miles or the 5.9 with 12k miles ever cracked.

Hunter

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post #9 of 11 Old 10-22-2016, 09:15 PM
Candymancan
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I wouldnt know if mine was cracked. I havent looked.. But if they were i havent had issues yet.
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post #10 of 11 Old 10-24-2016, 09:03 PM
Bodybuilder21
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I'll sell you my stock 5.9 heads if you're interested...dropping Edelbrock RPM's w/ Harlard Sharp roller rocker's+ Mopar Perf. valve cover's soon

98' 5.9- racejeep build (boosted 408 dreamin')
96' 4.0- 5.5"- currently torn down for 4.7 stroker
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post #11 of 11 Old 10-25-2016, 06:12 AM
Timo_90xj
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Quote:
Originally Posted by Bodybuilder21 View Post
I'll sell you my stock 5.9 heads if you're interested...dropping Edelbrock RPM's w/ Harlard Sharp roller rocker's+ Mopar Perf. valve cover's soon
You're gonna love the Edelbrock RPMs, trust me!

I'm using Comp cams ultra pro magnum roller rockers, went with 1.6 ratio.. was thinking 1.7s which probably would've been a good idea for a bit more valve lift.

Btw., beware with the Mopar performance valve covers that they might be a tight fit. I had to lift my A/C compressor 3/8" using DIY spacers and longer mounting bolts, because compressor A/C service nipple was hitting the valve cover. Also, there was not enough room on the passenger side between the PCV valve and A/C hard line. My covers were 100% original Mopar performance covers - Jeep- ones which should be a direct fit - but nope.

1998 Grand Cherokee 5.9 LX daily driver, 1.75" BB, 32" KM2s, HPD30 Eaton e-locker/D44a stock LSD, 4.56 gears, custom- fabbed tube bumpers and tube fenders,...


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1990 XJ Limited (4-door), 4.0 I6, AW4, NP242, ***rolled and totalled @ 165k miles***

***Under construction***
1990 XJ (4-door), 4.0 I6, AW4, NP242, PBR 42" tires, Unimog 404 portal axles, 110" WB, full cage + uniframe completely rebuilt, front 3-link + panhard / double triangulated 4-link rear,... ***SOLD***
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