Anybody ever seen a gt40p cracked head ?  I have not heard of this being an issue on Explorers. Where do they crack?

I've seen several cracked, and dozens of Explorers in junkyards with seemingly nothing wrong with them (no accident damage, etc.).  Around here, if you can't sell a decent looking SUV to one of the many fairly recent arrivals from Mexico, Guatemala, Costa Rica, etc. there's got to really be something wrong with it.  Now, it could be a blown trans, etc., but...

The big difference here may be that farther north we can get well below freezing in the winter.  I'm wondering if that's the difference between DE and TX or AL.  The ones I've sen cracked were either cracked in the deck surface from a coolant passage to a head bolt hole, or cracked on the exterior end from the core plug hole to one of the bolt holes.

MS wrote:

Sounds like freeze related.  What is this “freeze” phenomenon, anyway?

We just don’t see that around here.  Kind of like that other thing...  What’s it called?   Rust???

ok, I've been thinking, usually I fall asleep but it occurred to me to ask another question.  if you were to put an after market set of heads on a 89, 5.0 engine. would those valve springs be too stiff? here is my thinking for this question. if the valve springs are to soft on a set of GT40 heads to put on say a 289 why wouldn't the others be to soft?  

so, match everything. I understand that had read it before. now another question are all heads as far as the valve spring pockets machined to the same depths?  so if you buy the cam and springs as a package and you tell them what heads you are going to use, everything should be golden? no need to check for coil bind or anything?

In general the springs aren't going to be too stiff.  Springs are designed to permit a set amount of cam lift without going into destructive coil bind.  I'm sure there's some ridiculous situation where you have springs rated for a 9,000RPM NASCAR cam, but that's not what a typical aftermarket head is going to have.  Typically the springs are going to state they are good to 0.500, 0.600, etc.  Anything below that is not going to be an issue.  Its never a bad idea to check for coil bind though.  On any engine I build except a dead stock one I always check for coil bind, I check PTV clearance, valve train geometry for proper pushrod length, etc.  Its really easy to check these things on an engine stand, and it beats trying to figure out what went wrong when the engine is in the vehicle and broken. 

Its not really a case of the springs being too "soft" either.  Its a case that they can only take so much lift before the coils physically touch (coil bind).  Imagine what happens when those coils slam together.  Eventually they break, then nothing holds the valve closed.  A valve drops into the chamber at the wrong time and, well, Alpha Mike Foxtrot. 

The stock springs in the GT40s, or any stock head, are designed to handle the lift a stock cam has, with a safety margin that makes it okay to run a slightly taller profile, but not typically a real performance grind, as most of those are going to be close to or more than 0.500 lift.