can'tstopjeepen

Was there a difference between 0630 and the 7120 heads? I am wanting to put the 0630 on my zj and cannot see any noticeable difference. Everything I have found online says everything is the same. Any help?

okcjeeper

Just look at everything that's mounted to the head and compare. If everything is the same should be no issue to bolt right up.

98 JeepJeep

i believe the only major difference is 7120 has the coolant sensor on the back of the head and 0630 is on the thermostat housing. other than that they are very simular.

5-90

The 7120 head (1991-1995) breathes slightly better than the 0630 (1996-1999) head. And, the 0630 head does not have the port for the temperature sender in the back as mentioned (I had to go look - I have an 0630 out in the garage...) but that's easy enough to plug up. The best way to do it is with a brass 1/8" NPT plug - second best is to leave the sensor in place (the plug is simply stronger, and will hold pressure better.) The boss for the sensor is present on the 0630, so it could probably be drilled and tapped for the sensor (not germane to what you're doing - just a passing random thought.)

All of the 242ci heads will take either of the 242ci thermostat housings, so you can either have a 3/8" NPT port for a sensor (1991-2007 housing) or not (1987-1990 housing.)

Note that you may have some difficulty getting the exhaust ports fully covered if going from the 0630 head to the 7120 - there were two generations of heads after the 7120 (0630, 1996-1999 and 03312, 1999-2007) and the exhaust ports were reduced in size both times as an emissions measure (the smaller ports allows the exhaust gas charge to stay hotter, which heats the catalytic converter to operating temperature faster.) An adapter plate may be required, or just get an exhaust that will work with the 7120 head (most aftermarket manifolds will serve, as will an OEM from your model, 1991-1995.) Small ports into a big tube isn't a problem - but big ports into a small tube can create problems.

GottaMX

I just had to replace my head. The guys at the head shop said that they cost the same buch they WILL NOT interchange and work properly.

98 JeepJeep

thats because he is going off casting numbers and to be on the safe side he wants to keep them the same. to avoid any problems.......

can'tstopjeepen

5-90- I am going from the 7120 the the 0630. I know its backwards but it was the best one at the pull n save. Only 107 000 miles for 30 bucks. Cleaned up good. I will keep the sensor plug in in the back instead of capping it with something else. Plans got changed for finishing it this weekend but I will let you guys know when it is done.

GottaMX

$30 is a good deal. I paid $275 for my rebuilt head. I hated to pay that much but my XJ is my DD and the head shop I got mine from is supposed to be the best around. I found it was easier to pull the head, intake, and header all as one unit and install them all as one unit. Make sure you have 3 guys around though, 2 to lift the unit and 1 to keep the gasket lined up and lines out of the way.

BuckB91XJ

X 2 on the 7120 head casting being a better breather. All of the research I've done has stated that the 7120 is the best flowing head ever put on a 4.0. Since you're using the head for a rebuild just do some porting and polishing on it and have a good 3 angle valve job and rebuild done on it and it should flow as good as any. If you can get your hands on a 99+ intake manifold the word on the street is that it will add 25 ponies to a 91-95 HO 4.0 motor.

5-90

What's wrong with your 7120, and where are you? I've been trying to get my hands on a 7120 head for research for a while, but no-one has had one that couldn't be saved (since I plan on sawing it up anyhow...)