Replacing heads on a 4.0 OHV...

[AceOnGuitar]

Hello,


I have an explorer sport with a 4.0 OHV and 183,000 miles. I blew a head gasket, and so I am thinking of replacing the heads, too.

My question is, will the new heads be too much for the older bottom end? Will it be too much compression? Or will it be ok?


Thanks!
Chris

 

[Creager]

Only way to really tell will be to remove the heads =P

Check out the condition of the cylinders, check around the top of the cylinder, see if you can feel a ridge. Also look at the cross-hatching on the walls, can you see any vertical lines? Too much vertical scorching will make it easier for stuff to blow past the rings. With 183k, you are definatly going to feel something, you just want to make sure the wear isnt too excessive.

In all honesty, the bottom end of a 4.0 is known to still be in good shape after 200k miles. A new set of heads is all it probably needs. The main thing i would be concerned with would be the condition of the cylinders, and the engine bearings. As long as the engine hasnt experinced any oil/coolant mixing, which could cause bearing scorching, you should be fine with a nice set of heads.

 

[rmcknight]

200K on a 4.0 V6 is about the limit for the crank bearings - if you are doing up the top end. If you plan on keeping it for a few more years, i would pull the pistons and replace the lower end bearings as well - the cylinders should be ok - you just need new bearings! (for the $100 bucks, id do it, because if you dont you will have to do all the top end again!)