So I am currently mid way rebuilding my 4.6 for my 2003. The problem I ran into was the machine shop messed up my block to the point I need a new one. They ended up buying a engine for 700 dollars, I have no idea what state it was in, they just said that the deck of the block was in good shape and there is rust in the cylinders and they recommend boring out the sleeves and getting new pistons that match the boring (I think they said .002 of a inch bore but I can't remember what they said).
Now my concern is I am worried about the sleeves already being in bad shape, and was thinking that making the sleeves thinner will make more issues than I want (for example cracking or slipping sleeves). I will want them to pressure test the block and make sure that the sleeves are in good shape.
My overall question here I have is this, should I 1.have the shop bore the sleeves and get new pistons 2.reline the cylinder with new sleeves or 3.prepare the block and get top hatted sleeves (I would prefer this option but the cost is somewhat out of my price range but if it is worth it then I might do it). Any thoughts would help!

 

Land Rover only makes 2 sizes of pistons. The "A" stamped pistons are for clean, early blocks and the "B" oversized pistons are for late model 4.6 engines or early 4.0 motors that got bored.

I say this because if your shop is boring your block, you need to know that the "B" pistons are large enough to fill that new bore... but if they are only getting rid of rust then they may be talking about honing or cross-hatching instead of boring. A simple scothbrite pad and some elbow grease will often clear cylinder rust.

You've got to spray WD-40 or some such into each cylinder to keep away rust after your engine disassembly. They will rust up overnight. Same for the crank unless it is in cosmoline prior to (never during!) installation.


A clean new block is just $600 (already pressure tested!). I wouldn't grind an old block if the labor is going to be $600+.

As for top-hats, they are fantastic, but won't give you anything different than all-metal headgaskets will give you.

 

If they are so rusted that they need bored, that's alot of rust.
Some light surface rust would be normal, and easily cleaned by honing, not boring.
.002" is 2 thousandths of an inch(about half the thickness of a sheet of paper). They more likely said .020", 20 thousandths.
I am not sure what over sizes pistons are available in for these engines either, and they need to know that Before they bore it.
New pistons are also $800ish a set(all 8).
I would be concerned boring out an already thin liner.
That would make it more suseptable to heat, and also increase it's chances of slipping(but I'm not saying it definately will either).
If it were me, they could eat that block and find me a good one.
FYI, a 4.0 and a 4.6 use the same block, only the stroke(crank and rods) are different.
So you could get a 4.0 block and use that also.

 

I thought that the difference between the 4.0 and 4.6 was stroke, not bore size.

 

Any info I ever found was that yes, there's an A and a B, and one is the first and only oversize(can only be bored x amount once).
I don't know how much bigger the oversize is either.
I never heard that some engines came with one size, and others with the 1st oversize.
I need to measure the o.d on my 4.0 vs 4.6 pistons now.

 

After some digging, the difference in A to B pistons is miniscule...4 decimal places.
Consider it this way, boring a small block Ford or Chevy .030 will gain you roughly 4 cubic inches...30 thousandths.
For the LR A to B, we are talking 1 to 2 10 thousandths, with .0003 being the widest difference.
I can't belive it's even relevant.
Forget boring, you can hone that much!

 

The smallest "A" piston in spec would be 93.97 mm while the largest "B" factory spec piston could be 94.00 mm. Max clearance between installed piston vs bore liner to still be in spec is .045 mm.


That 4 decimal place nonsense is surely a factory typo or 2... NOTHING in these old engines is that precise! Lots of room for error and sloppiness. We'd need 0W20 synthetic oil if clearances were as tight as 4 decimal places...

These machines are the AK-47s of the 4x4 world. Fill 'em with mud & bash down a fence with them, they'll still function. Heck, we can run 20W50 oil in them if desired.

 

And you are correct, except the engine molds were past their shelf life so by 2003 there was a tiny difference in bore size so the factory used the "B" pistons.

2003 and 2004 models have maybe ~~1.2 ci bore difference compared to earlier 4.0 motors. Miniscule. Instead of 280.7 CI our late model 4.6's might have almost 282 ci displacement. Considerably less than 1% difference.

Too small to count, especially since it was a function of engine mold overuse instead of by design.

 

So I got with the machine shop today and discussed things with the new block. They were telling me that this new block is in better shape than my old one (cylinders are worn down less and the deck is in better shape and the casting of the block is better). This new block was also not involved with a overheating or engine failure so it should still be in good shape. The reason why they want to bore it out is because there is pitting in a couple cylinders. Their plan is to bore it out .020 of a inch and get bigger pistons (they found some for about 750 dollars I think they were telling me). If I were to go this route, I am for sure upgrade the cooling system to lower the temp for sure. I am just not certain if I still want to bore out the engine since these liners are already a major failure with these engines. If I had enough money i'd go with RPI and get their blocks but it's just not affordable for me right now (being a poor college student is fun). Tomorrow I will talk with some professors at my college that have been in high performance automotive racing for 30+ years and get their ideas. Thank you guys for all the help!

 

I am runninng Valvoline 20x50 vr1 oil in a newly rebuilt engine. No problems so far. The shop recommended to use that oil as it is for flat tappet engines like ours...