Topic: 2.5 cylinder head size difference?

[dudley]

Is there a difference in the width of the 2.5 heads between the TBI and the MPI heads, specifically where the intake and exhaust manifolds attach?

[chardrc]

i did a check at autozone.com comparing 1990 (tbi) to 1991 (mpfi) and they came up with the same part number for the head(s). but i wouldn't count that as hard evidence that they are exactly the same. go luck on this search as i have been looking at getting a header but don't want to run into problems...

[chardrc]

sorry for double post but i forgot to mention 1 thing and i still can't figure out how to wait like 30 seconds for the edit button to automatically appear. i looked at the parts catalog for 1990 jeeps and it gives a different part number for fuel "injected #2403" and "carbureted 2405" the difference i do not know but the numbers i do.

[dudley]

sorry for double post but i forgot to mention 1 thing and i still can't figure out how to wait like 30 seconds for the edit button to automatically appear. i looked at the parts catalog for 1990 jeeps and it gives a different part number for fuel "injected #2403" and "carbureted 2405" the difference i do not know but the numbers i do.

I know there are some combustion chamber differences to raise hp through compression ratio, and that may be the reason.   Plus, I could see, as years go by, the later head, even if a bit different in compression ratio (highter) and if a half inch wider, replacing the early ones since they would bolt on and not be a problem irt intake and exhaust.  When I worked at a Ford Parts counter, there would be such replacements of earlier with later.  Again, I ask because an 86 and 87 2.5 had the same fit problem for Clifford header while a later one did not.  Just wondering if they did not increase the runner length in the head a bit, say a half an inch, for the MPFI over the TBI.

[pioneer4x4]

would the 90+ heads work on earlier models?

[dudley]

would the 90+ heads work on earlier models?

dunno.  There would be compression ratio changes probably. 

[Mr_Random]

I'm pretty sure that the XJ kept the 9.2:1 ratio through it's years.
The YJ, from 87-90 was 9.2 also I think, then dropped to 9.1 from 91 until the release of the TJ.
The TJ always had 9.2:1...

Now, something changed from 98 up, all I can remember is that each piston has a different diameter tolerance, almost like each one was a different size... weirdness?

Correct me if I'm wrong!

[dudley]

Anywho, back to the original post.  Do any of you have heads from a MPI engine and a TBI engine sitting around to where you can compare the distance from probably the head bolt next to the intake/exhaust mating surface and that surface to see if there is a small distance change?  Since Clifford says they have not modified their Jig for the 2.5 header since 1986 and both an 86 and 87 engine had the problem of it touching the block, but a later one did not, I am confused since neither the 86 or 87 should have had that problem if it is really true Clifford has not changed the jig since 86.

[Jeffy]

http://4bangerjp.com/forums/index.php?topic=936.0

[dudley]

http://4bangerjp.com/forums/index.php?topic=936.0

I had already looked at this thread and it did not say anything about dimensions, only casting numbers and combustion chambers.  The pictures on this thread makes the heads look the same dimensionally, so there probably isn't.