Cracked head 4.0L Jeep

[RockPaws]

After finding coolant in the oil, I removed my cylinder head. After the usual cleaning and tear down, we magnaflux the head. No cracks around the combustion chambers, this is normally where a crack will be found. After another pressure test of the head, we found the crack. Forward of the #4 exhaust spring seat was a leak or crack about 1/2" long. When magnafluxed the crack was 5" long and traveled to the right around the rocker arm boss and down into the push rod hole.
I checked with a few machine shops and HESCO. Jeep 4.0L heads are not know to crack in this area. Figures I would be the lucky one.
Anyone else ever find a crack on the top side of a 4.0L head??

 

[RockPaws]

Well, I picked up my new head from Josh at LHM Jeep Monday. Very nice casting. Inside the water jackets looks better than the ports on my original head! I completed the port and polish, and match ported the intake manifold to the head. Opened the exhaust ports up a little to improve the flow into the new Banks Torque tube header. I had Glen at Parts Connection complete the head work. They also found the new head was warped a little, about 0.005" . Service limit is 0.008" max. They surfaced the head, its now dead flat. Their machine cuts so well, it gives you a mirror finish! Nice 3 angle valve job, the valves all hit in the middle of the valve face and are very lightly lapped to ensure perfect contact.
Reinstalled the new head Saturday, and had it running by the afternoon.

The modification upgrades paid off. Better off the line and pulls harder above 3000 thru 4500 RPM.

Frank

 

[Jared]

How much did that long list of services run you? New head $?

Jared

 

[RockPaws]

How much did that long list of services run you? New head $?

Jared

New head was just under $400 thru Josh at LHM Jeep.. Thats a bare head casting, no valve parts at all. I replaced 4 intake and 2 exhust valves (I used the origional valves that were still servicable.
As far as the machine work, I actually haven't been billed for the services yet. I have an account at Parts Connection, should know soon. They did the surfacing, and 3 angle valve job. Porting, I do my own work, and don't have to charge myself. It took me a good 10 hours of work, which I would nomally charge about $400-500 all depending what someone wants done.