ARP head studs are reusable. Switch to them.

 

You may be able to tell if the threads are stripped just by inspecting the holes. You can also try to thread an old bolt in. It should thread in smoothly. if not, it might be stripped. If they are stripped, you might want to be careful about just drilling them out and installing an insert. There isn't too much extra material to play with in a 4.6 block. Hopefully someone else who has dealt with this can confirm if this can be done without concern.

 

This is a good point. The 4.6 certainly has its weak points. You don't want to find out the hard way if this is one of them! It is a common problem though. I'm sure someone has tried this before.

 

Mines actually a 4.0. Ran the bolts in every thread for the head bolts. The two on the inside edge on both sides of cylinder 5 are rough. When I took the bolt out, some threads came with. Looks like time sert fix on this one. I see on time sert's website they make a kit specifically for these engines. Am I reading this correctly, are the threads standard and not a metric thread? I have a bunch of time sert kits at the shop but they are all metric.

 

I've never checked the threads on the head bolts. I guess they could be standard.
That's probably good you have the 4.0, I've never owned one, but they do seem to be more durable overall. If most of the threads feel okay, I would probably just do the ones that are rough. You know what they say about Rover's? If it ain't broke... it will be! LOL!
Better not to risk doing them all.

 

I was gonna say......."4.6 block"? There isn't such a thing, there is only one block and this is a 99 DII we're talking about........

The cam, crank, con rods, pistons make it either or. I would not bother fixing a block with stripped head bolt threads. Used blocks in good condition are not that much when compared to a professional thread repair job. Not worth the time and effort, aint that special or rare to save it.

I've used TTY head bolts in aluminum engines (not just Rovers) without a problem for many years, not had any issues. ARP are awesome but spending that kinda cash on a low horsepower engine, personal preference..... Yeah they're reusable which means they don't stop head warp and I don't think they'd do much for damaged threads - if that's the case.

7/16" UNC, 14 threads per inch.

 

The problem with the 4.0 vs 4.6 is first an added stress issue that the 4.6 exerts and second a tragic issue of quality control.

From 97-02 Land Rover used ultrasound to measure block wall thickness. The best blocks were used in the 4.6 motors, range rovers. Ask any rover mechanic and they will tell you they have seen dramatically less failures in the RR 4.6.

By 03/04 Land Rover was only producing one motor, the 4.6. So all the different grade blocks and probably back stock that didn't even pass as the lowest grade were being used for the Disco 4.6 motors.

03/04 4.6 motors are a crap shoot.

 

I should have included more detail in my post so Abran wouldn't have had to do it for me. The reported issues with the block quality for the 4.6 motors in the Discovery is what makes the chance of the block thickness at the bolt holes being a problem more of a probability. The molds were supposedly pretty worn by the point the 03/04 blocks were being cast and their lack of quality control (as evideenced by the liners not even being pressed in to the machined lip in the block) resulted in some really thin areas along the jackets. The blocks used for the 4.0 seem to be more consistent so using an insert may be fine. Buying another block won't cost much, but it will require you to pull the motor so an insert should be much easier overall. Unless it fails. Also, they are SAE threads just to keep things interesting. Very British.

 

What I meant was the 03/04 blocks. Which I thought were a little different. Didn't they get rid of some head bolts on them or something like that?

 

The pistons are identical. The blocks used in the 03/04 Discovery's are truly pathetic and they are all 4.6 liter engines. They have a tendency to crack. The 4.0, though it's the same shape and size, seems to be more reliable. That's what I was talking about. Not that they are a different block, per se, but quality changed drastically from one displacement to the next.