Need HEAD... but which one?

jackdaniels

NAXJA Forum User
Location
Colorado springs
so i have a 99 xj and am wanting to snag a head for it to start rebuilding/ upgrading. so the big question is where can i find a cross reference manual or guide?

what years will work?
what to look for?

read through alot of stuff but i guess i am just not finding the info i want.

could this quite possibly be a future cross reference sticky?


NAXJA
 
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You can use either the 7120 head(91-95) or the 0630 head(96-99). The 7120 head has an additional coolant port on the driver's side rear that can be plugged with an old sensor, but other than that, it is identical to your 0630 head. Get one out of a Jeep that doesn't look like it's been overheated(look for indicators). I just replaced the head on an 01 w/ a new improved 0331 casting($375). The previous owner got in an accident that tore up the radiator and she obviously overheated it leaving it on/driving it home or whatever. I've fixed a couple XJs whose heads and valves were warped from an overheat.
 
so i have a 99 xj and am wanting to snag a head for it to start rebuilding/ upgrading. so the big question is where can i find a cross reference manual or guide?

what years will work?
what to look for?

read through alot of stuff but i guess i am just not finding the info i want.

could this quite possibly be a future cross reference sticky?


NAXJA

That's why I'm writing Swappology...

As mentioned, you can use the 0630 or 7120 head without incident. NB: If you use the 7120 head, make sure to use the exhaust that came with it, or use an aftermarket header, as the exhaust ports on the 7120 are larger tahn the 0630. Using the 0630-compatible manifold can lead to reversion problems and a loss of performance.

Valvetrain is otherwise identical. Intake ports are compatible between the various 1991-up manifolds.

Now, what else would you like to know?
 
Not to question you Kelley, but I've never noticed a difference on the exhaust ports between the 7120 or 0630, nor a difference with the headers between the two(I've spent most my time w/ 91-96s). Now when talking of using a 7120 or 0630 in place of the 0331 w/ small exhaust ports it is true that the smaller 0331 exhaust manifold will not cover the larger exhaust ports of the 7120 or 0630. To make matters more interesting, my 1/96 0630 head has the coolant port in the back of the head and sensor to feed dash gauge. The 97s with their newer style dash and bus system did away with that rear coolant sensor in the 0630 and got the info from the cts in the t-stat housing.
 
Not to question you Kelley, but I've never noticed a difference on the exhaust ports between the 7120 or 0630, nor a difference with the headers between the two(I've spent most my time w/ 91-96s). Now when talking of using a 7120 or 0630 in place of the 0331 w/ small exhaust ports it is true that the smaller 0331 exhaust manifold will not cover the larger exhaust ports of the 7120 or 0630. To make matters more interesting, my 1/96 0630 head has the coolant port in the back of the head and sensor to feed dash gauge. The 97s with their newer style dash and bus system did away with that rear coolant sensor in the 0630 and got the info from the cts in the t-stat housing.

Hm - OK. I haven't gotten a 7120 head in stock yet for direct comparison. It may be that the volume of the port was reduced without reducing the port exit significantly, and for a similar reason to why they reduced the port further for the 0331 head (maintain exhaust gas temperature retention to improve catalyst light-off time.)

I recall noting somewhere that the 0630 port was smaller than the 7120 - but that could be it (or I could just have my wires crossed. That's why I'm collecting heads. Anyone near San Jose, CA with a cracked/warped 7120 and/or 0331? I have a 2685, two 2686, and an 0630 already...)

It's worth noting that the 0630 head still has the cast boss for the gage driver, it just isn't drilled/tapped. I have yet to check this, but it's fairly likely that the head would support having that spot drilled/tapped 1/8" NPT as well, if you don't mind doing the work (just be careful how deep you run the tap. The taper can cause you trouble if you go too far down...)

I find it interesting that you've got an "early 0630" head that still seems to be OBD-I - as you noted, it was OBD-II that used the unified CAN bus to drive gages and engine management. Which style of IP do you have? The fact that you've got that hole drilled/tapped, tho, lends weight to the previous argument (the boss is simply unmachined, and that may be corrected at will.)
 
To make matters more interesting, my 1/96 0630 head has the coolant port in the back of the head and sensor to feed dash gauge.

My August-96 0630 head has the coolant port with a sensor for the dash gauge and it's OBD II (allowing me to go through the OBDII line at the smog station.) Did not have any issues putting the sensor in the 7120 I replaced it with.
 
Quit screwing around and go Hesco. They have a reery nice aluminum head. Adds 20 hp on it's own...but costs $2000...
 
Quit screwing around and go Hesco. They have a reery nice aluminum head. Adds 20 hp on it's own...but costs $2000...

Not on its own.. you still need other mods.
 
Quit screwing around and go Hesco. They have a reery nice aluminum head. Adds 20 hp on it's own...but costs $2000...

You could potentially gain as much as 25hp but only if you also have Hesco's RVOB cam plus other airflow-enhancing mods.
 
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