Cracked 4.0 head on 258
MattandOrange
Jeeper
I've got a crack on #3. It was typical of the casting number that I had but I took a chance on it. Do I scrap it or can I repair it?
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Cracked 4.0 head on 258
- Thread starter MattandOrange
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1986cj7
Senior Jeeper
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- 1986 cj7 258, t-176 4-speed, d-300, moser one piece axle in back in amc 20,G2 4.10 gears front and back, detroit truetac front and back,G2 4340 chromoly front axles in a d-30, 4" rough country lift, 33" tires
what was the cast # I'm in the process of collecting parts for a build of my AMC 258 i6 / 4.2l and would like to avoid this. Also what head would be best for the build?
MattandOrange
Jeeper
The 0331 heads are prone to cracking. 7120 is most desirable. I found a 0630 for cheap that's ready to go.
'87-'90 - 2686 Non-High Output
'91-'95 - 7120
'96-'99 - 0630
'99-'01 - 0331
'87-'90 - 2686 Non-High Output
'91-'95 - 7120
'96-'99 - 0630
'99-'01 - 0331
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I would toss it and find a 7120
MattandOrange
Jeeper
I found a 0630 for $100. I've only heard of lousy things about 0331. I'm thinking the 0630 is worth a shot.
Tin Medic
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7120, just do it once and be done.
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73CJ
Crazy Sr. Respected Jeeper
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The 7120 has been fine on mine.
That's the one everyone who's done it recommends. Lots out there just keep looking. Sometimes you can get a blown motor for real cheap.
That's the one everyone who's done it recommends. Lots out there just keep looking. Sometimes you can get a blown motor for real cheap.
IOPort51
NOT the voice of reason Jeep-CJ.com
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I had a crack in a 7120. If the price is good, go for it.
I think Jeep heads crack, all there is to it.
I think Jeep heads crack, all there is to it.
coldair
Full Time Jeeper
I have a 0630 on my motor there really isn't any diffrence between 7120 and the 0630 head. The only diffrence the older 0630 they have a water temp sensor port the never ones don't. Mine has 1997 as a casting date it doesn't have the port for it.
Last edited:
1986cj7
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- 1986 cj7 258, t-176 4-speed, d-300, moser one piece axle in back in amc 20,G2 4.10 gears front and back, detroit truetac front and back,G2 4340 chromoly front axles in a d-30, 4" rough country lift, 33" tires
Thanks for the info Orange
I guess I should be looking for intake and exhaust manifold with it. Do they flow better then the AMC 258 i6 / 4.2l manifolds and or would they even fit? I've read that some will bolt up and some have to be fabbed up to work, what's the real deal?
Last edited:
Niedhogg
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'76 CJ5, 232 ci, T-150 3-speed, D20 T-case, Corp. 20 rear w/full float axles and lockout hubs and Detroit auto locker, D30 front w/lockout hubs, gear ratio is unknown..
Can the 4.0 heads be installed on the AMC 232 i6 ?
coldair
Full Time Jeeper
I've read you can install it on the AMC 232 i6 .
Niedhogg
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'76 CJ5, 232 ci, T-150 3-speed, D20 T-case, Corp. 20 rear w/full float axles and lockout hubs and Detroit auto locker, D30 front w/lockout hubs, gear ratio is unknown..
I'm not trying to hi-jack, but from what I know, AMC 232 i6 and AMC 258 i6 / 4.2l blocks are the same and one is a bit below 4 liters and the other is a bit over, so it could benefit a AMC 232 i6 as well as a AMC 258 i6 / 4.2l , correct? At the very least, if you were to use the fuel injection with the 4.0 head...
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