Topic: Cylinder Head for a 92 2.5

[Jhcujo]

Hello all I want to say first off this is my first post here so forgive me if this is in the wrong place. First question I would like to know if a head off of a 88 2.5 Cherokee with a carb will work on mine? There is one in a local boneyard that I am looking at. Second I want to kind of rebuild in stages top end first then the bottom does anyone think that will be a problem? I have only had her for about 5 months but I have done a good bit to old girl. I have the 4.0 TB and spacer, electric fan, and K&N filter and intake. The main reasons for doing this in stages is money and daily driver. So I want to get a different head do some work to it put it on and then bottom end later this spring or summer.

[hopp]

I am aware of at least two different 1/2" head bolt cyl head designs for the 2.5L
They are compatible with one caveat(to the best of my knowledge).

You can locate the casting # on the drivers side just above the #2 intake port.

Casting #117 -- closed chamber 51cc volume.

Casting #403 -- open chamber 61cc volume.

If the casting # is the same it should work just fine.

[Jhcujo]

Thank you for the information. I will check

[Jeffy]

Do you have any idea when they changed the heads?  (Although I coule probably guess.)

Pro's and cons of each, pictures?

More information would be nice for the Faq.

You can make a new post in the Feedback and I'll move it to the Faq.

[hopp]

I think they changed the heads in '91. I got my first tidbit of info here:
http://www.aera.org/fm/archive/index.php?t-77.html

The post caused me to start looking into head casting differences. I have a couple casting #117 with one more on the way but I don't have any #403.

The CH150N is based on the #403 casting.
Here is a link to a picture of the #403 head:
http://www.lightningcylinderheads.com/stockreplacementheads_files/ch150n.gif
Notice the large D-shaped combustion chamber.

The #117 chamber is smaller and more 0-shaped with a slight protrusion for the spark plug hole. I'll upload  pictures of the #117 as soon as I find my pcmcia adaptor.

I currently don't have a burette to cc the heads, but I will eventually.  Have you noticed how hard it is to come by lab glassware with the worries over terrorism and meth labs? :?

It does look though like the #403 has more area. I think they switched to the closed chamber #117 design to get better quench, scavenging and boost the torque a little.

Matter of fact, checking for the remote possibility of piston interference issues, I'd personally switch to a #117 on an engine currently equipped with a #403(when it's time to do the head).

On a slightly unrelated note, I think I can use 4.0L roller rockers on the 2.5L I'll let you know how that pans out.

[Jeffy]

4.0L rockers will work on the 2.5L.  It's been done before. Gary on the mailing list seems to be the rocker guru.

[supryj4]

hopp you had talked about piston clearance problems do you have any more info on that because I am thinking about swaping my #403 for a#117 I allready have. thanks for any info

[hopp]

You are in a great position to determine clearance. Look at the depth of the valves in the chamber on the #403's and look at the depth on the #117.
If the valves are both the same depth from the head surface(and same angle in the head)  you will be fine.

I think that the volume difference is due to chamber shape and not valve position, but I don't have a #403 to check.

[supryj4]

I have two spare motors I know one is a 117 the other one is in storage I will try to get over there and pull that head off I think it is a 403 and I will mesure and let you know. Also am instlling a hesco RVOB cam and I was thinking of using that 117 head.My current motor is a 90 with a 403. Does any one have an idea about what it should cost for rebuilding, polishing and porting of that head?

[Jeffy]

If you can take some pictures for me.  I'd like to add this to the FAQ.