Engine Dated Gt40 Heads

Discussion in 'Fox 5.0 Mustang Tech' started by AMCman10, Sep 24, 2013.

  1. Hey guys, I'm looking for a little knowledge that I haven't been able to pin down. I'm pretty new to Fords, but have done tons of research and have a pretty decent idea of parts and such. On to my question....

    I've got a set of GT40 heads. They are cast F1ZE-AA, so off of an Explorer, I presume. My question is about the date and letters that are on the front of both heads right under the freeze plugs on the milled part of the head. They both have "10/94" and the letters "PBF" on them.

    I'm not asking because I think I have something special or anything, but curiosity is getting the best of me! Haha.

    Thanks a lot, guys!
  2. 10/94 is the cast date

    PBF- Powered By Ford
  3. I knew it would be that easy! Amazing that I came up empty trying to figure that out (although the date was pretty obvious). Thanks a lot, Mike!
  4. F1ZE are GT-40's but not off an explorer.

    Do they have thermactor ports?

    Cobra or lightning or marine application could be the source. Difference would be the stud diameter and if they use the thermactor ports or not
  5. Hmm, the casting number charts I've seen said Explorer, but like I said, I'm still new to Ford.

    Yes, it has thermactor ports. And the bolt holes are 1/2". With all the reading I've done, people have been saying some Cobras and some Explorers had 1/2" holes. I Initially thought 351 until I started seeing that.
  6. Found this on another site.

  7. From what i'm reading online, the F1ZE head is a marine-application head that found it's way onto '93 Lightnings. A 10/94 cast date seems like it would fall into the ballpark of a Lightning head.
  8. Interesting, I've found a lot of conflicting data around the internet, haha. Now, I can eliminate them being from a '93 Cobra/Lightning because of the 10/94 production date, correct?

    Also, you guys are awesome, and I really appreciate the help!
  9. Seems those heads made their way into several applications. Regardless, I would swap out the weak springs for a set of either TFS or Alex's.
  10. Yeah, I'm really not worried about it, curiosity got the better of me. I've already rebuilt them with new springs, seals, and a set of Manley valves. They will be going on this weekend!
  11. If anything, i'd say they were lightning heads.

    1/2" head bolt size
    thermactor ports

    Marine heads did not have thermactor provisions.
    Only GT-40 head to use 1/2 head bolts was the 351 Lightning
    1994 cast date falls into range of lightning production.

    Ultimately it does not matter. If going on a 302, make sure you use sleeves to use the 7/16" head bolts, and replace the springs. I'd look up the CC size of the combustion chamber for early lightnings to figure out compression ratio
  12. Right, from what I'm reading, they had a slightly larger combustion chamber, but they would actually need to be measured. The heads came off a pretty damn stout 302, and were very well built, which makes me wonder if they've been milled.
  13. Yep. Def want to know if they were milled, as that impacts compression and alignment with the intake holes.
  14. Exactly. I'd like for them to be milled some to up my compression a little. But that's not a fun thing, to set the lower on and the holes don't line up!