Curious About Cracked Heads

[backslash18]

Can anyone tell me why the heads on four liter Rangers are so prone to cracking? Does it have something to do with the engine being bored out so close to its limits? The three liter and four cylinder engines don't have this problem so is it just a design flaw?

 

[MAKG]

It's just a design flaw. Head castings are a bit too thin in a critical spot.

It has nothing to do with "boring out to limits," as the 2.9L has even worse problems (and you don't bore a head).

The critical spots on heads tend to be around the exhaust valve seat and exhaust ports, as that's where a lot of localized heat has to flow.

 

[backslash18]

Yes, I realize you don't bore out heads... it was a poor choice of words. If I understand correctly the 4.0L is actually just a 2.9 that has had the cylinders bored out right? Obviously that oversimplifies it but I believe that is the basic premise?

Anyway, thanks for the answer MAKG.

 

[04 EDGE]

3.0's have the same problem, but it was a casting problem only for a few years per ford TSB

 

[shadetree]

Gross is correct, the castings are much too thin. They will also crack around the lower water passage holes into the cylinder. I had a Mazda, and an Explorer do that.shady

 

[Ranger44]

BUT, many of the aftermarket NEW castings correct this flaw.

 

[F150hybred]

I seem to recall the 2.8 having an issue with cracking heads too. That would put almost all the engines from that design into the cracked head area. Only one I'm not too sure on would be the 2.6.

 

[JOKER86]

It's just a design flaw. Head castings are a bit too thin in a critical spot.

It has nothing to do with "boring out to limits," as the 2.9L has even worse problems (and you don't bore a head).

The critical spots on heads tend to be around the exhaust valve seat and exhaust ports, as that's where a lot of localized heat has to flow.

i know all too well about the 2.9, lol im on my second set lol the first set of origanals split between the valves

 

[turbo cat]

Yes, I realize you don't bore out heads... it was a poor choice of words. If I understand correctly the 4.0L is actually just a 2.9 that has had the cylinders bored out right? Obviously that oversimplifies it but I believe that is the basic premise?

Anyway, thanks for the answer MAKG.

the 4.0 is stroked and has a taller deck hieght