UPDATE

Since installing the new HV oil pump, there really IS more oil circulating in my engine. It really evident when I pass on the interstate. MAN! Sorta like my old Diesel Bonneville. Mostly black smoke with a hint of blue. It does go away though. lol


1992 XJ, 250K hard miles by previous owner....


Since failing miserably to find a decent low mileage motor within 1000 miles for under $900, I decided to swap out the oil pump for a Melling High volume one. Hoping that I can limp the old girl along till I can track down a fresher engine for reasonable $$.

Noticed several drops of fresh coolant hanging off the cam, rods and mains while I have the pan off. *sigh* It never ends does it...

I didn't think the 7120 heads were prone to cracking? Is the 7120 head crack prone? Anyone have a similar experience? A failing head gasket would fail along the cylinder from what I have worked on in the past. Cannot see it failing between a coolant passage and the oil returns..

I need to finish wailing on my oil pan to get the pump to clear, but should have her all buttoned up this evening.

You CAN replace the pan with stock suspension. Just use a floor jack to raise and lower the front axle as you wiggle the pan around. Sucks, but it can be done.

If my oil pressure improves, I guess I need to pull the valve cover and see if there are any obvious cracks on the top. Otherwise I will drive it till it drops I guess.

 

Wellp, new Melling HV pump installed and a fresh fill of 10w30. Held 23PSI till it got hot then hangs at about 18 on the highway at 65. Drops down to the bottom of the gauge at hot idle still.

Oh well. Maybe next time. At least I have a HV pump for the next motor.

 

Nothing like talking to ur self on your own thread huh? Wish i had something encouraging to say but.... sorry dude

 

Is the #7120 prone to cracking? Not that I know of. Can it crack? Certainly - I've seen Hemi heads that were cracked!

However, an iron head typically cracks for one of two reasons:

- Casting voids. Granted, these have been fairly well ironed out in the last 40 years or so - with the advent of low-pressure die casting (the molten metal is forced into the mould with a pressure of something like 6-10psig, and the mould may be "flushed" with oxygen to assist in prevention of casting voids.)

- Severe overheating - although an iron head will typically warp before it cracks.

You may have ended up with a head getting warped - this would be caused, as mentioned, by severe overheating. A casting void (as mentioned in the first case,) is simply a time bomb waiting to go off, and you can't really predict when it will happen. (The first Hemi head I saw that was cracked I sectioned, and it had a void the size of a grape in the middle of the crack. The second was was severely overheated - got to something like 310*F on the coolant temperature before it gave up...)