Head differences

[jasonb]

Hello, this is my first post here though I've been lurking a long time while planning a build. I pretty much have my specifics lined out so I'll try not to beat any dead horses. I do have a few questions that I can't seem to find definitive answers to. First of all, my planned build:
96 4.0 block
96 4.0 rods
12cw 258 crank
Bulltear pistons, dished for 9:1 or so CR
*0630 or 7120 head*
99+ intake
JBA header
Crower 44243 cam

First question: Is there really any benefit to the 7120 over the 0630? Everything I find is anecdotal. Any real world evidence? An observation I've made is that the two look identical sitting side by side. Aside from the casting number the only difference I see is the dowel pins. Quite to the contrary of the differences noted in this article http://www.enginebuildermag.com/2004/10 ... der-heads/ , the ports look identical, valve covers are the same (same exact part number), both have bee hive springs.

Jason

[IH 392]

If that article was printed out I'd probably use it to wipe with!? photo #4 clearly shows a 258 head NOT any of the 4 4.0 heads

As far as I'm aware the only differences in the 7120 and 0630 are the temp sensor port in the 7120 and dowels in the 0630 deck.

[Cheromaniac]

As far as I'm aware the only differences in the 7120 and 0630 are the temp sensor port in the 7120 and dowels in the 0630 deck.

Correct.

[jasonb]

Oh, that reminds me... I was also going to note that I have figured out the temp sensor hole through my own observations. 96 0630 heads have the hole, 97-98 0630 do not. In 96 jeep used that sensor for the gauge, but by 97 jeep was using the t-stat housing sensor for everything. It probably had something to do with 96 PCM being different from 97-98, even though they are all OBDII.

Jason

[KYXJ]

This solves one of my lite headaches on my new build. I forgot about the differences in temp sensors between the 96 and newer heads. This might explain why my 1996 ecm isn't registering anything to the temp gauge on my 1998 4.6

[SIXPAK]

If that article was printed out I'd probably use it to wipe with!? photo #4 clearly shows a 258 head NOT any of the 4 4.0 heads

As far as I'm aware the only differences in the 7120 and 0630 are the temp sensor port in the 7120 and dowels in the 0630 deck.

My info has said that the early 7120 heads had a bit less material around the valve guide inside the ports. Foundry had trouble with core shift so later 7120 heads hada bit more material in this area.