4.6L V8 bore wear. How much is too much?

So given the LR overhaul manual doesn't specify a max bore wear figure, just a max ovality of 0.013mm, how much bore ware is too much?

I have one cylinder that's 94.11mm at its widest (side to side) and 94.08mm long ways. So technically out of round and way past the bore size for type B pistons of 94.030mm.

The rest are OK at around 94.05mm.

There is a max bore to piston clearance of 0.045mm, which is also pretty tight.

Am I going to be ok to just flex hone it and put new rings in, or should I get the whole block rebored by 0.1mm and fit oversize pistons?

(I don't really want to go to all the hassle of fitting top hats. The block has the lip at the bottom to stop the liners dropping)

Cheers!

I'm no expert by any stretch of the imagination but this is my thoughts...
For a start, you don't say which engine it is or when it was made, the 3.5 is a stronger engine as it's not been bored out using old, worn out land rover machines.
If it's a later engine and needed a rebore, then I'd go for top hat liners while i was at it. Whoever does that needs to do a proper job and have experience of doing it on these engines. Before any rebore, the block needs to be check that it's suitable, top hats aren't a 'fix all' from what I've read, though i have no experience to say that with any conviction

kermit_rr said:

I'm no expert by any stretch of the imagination but this is my thoughts...
For a start, you don't say which engine it is or when it was made, the 3.5 is a stronger engine as it's not been bored out using old, worn out land rover machines.
If it's a later engine and needed a rebore, then I'd go for top hat liners while i was at it. Whoever does that needs to do a proper job and have experience of doing it on these engines. Before any rebore, the block needs to be check that it's suitable, top hats aren't a 'fix all' from what I've read, though i have no experience to say that with any conviction

Click to expand...

Hi Kermit, Its a 4.6L circa 2002, its a later one as it has the liners retained with the lip at the bottom.

Ideally I'd like to pressure test it first of course but I have no reason to think the block is cracked. The engine suffered a loss of oil pressure due to the pressure relief valve sticking. The cam is toast so I have pulled the whole engine to check the rest. So far no other damage other than No.8 bore seems to be worn a lot more than the rest. This is probably due to the piston gudgeon pin bore suffering some wear, allowing the piston to rattle about too much. Anyway No.8 needs a new piston at the very least.

If the motor is going to run fine with a quick flex hone and a set of rings, I'm not going to bother with the large costs of re-linering the whole block (£1000). A middle option is all new pistons and rings and a rebore, about £500.

I was interested to know what the real world bore clearance and wear limits are, as oposed to what the LR manual says... They specify a max wear limit on everything expect the bores!