Says he with a 4.0. I prefer the 4.6, it's what my truck has.

 

I believe RoverMasterTech said something in a post that the top of the cylinder chambers are different on a 4.6 block. I was under the same impression as you. Maybe send him a PM or consult some more sources. If it were that easy I will start taking all my slipped liner 4.6 blocks and replacing with 4.0.

Start a new thread, lets see who comes out of the woodwork.

 

reliability-wise, because power-wise there's really not a difference, I've driven thousands of miles on both.

4.6s will always fail, always.

 

Blocks are the same (they do make later castings that are not as good as the earlier castings and then there's the crank sensor mount changes between gems and bosch which can be changed but, on a 4.0 bosch engine and 4.6 bosch the mounts would be the same)

Heads are the same, combustion chambers are the same, combustion ratio is different due to different piston geometry between 4.0 and 4.6.
Maybe that's what he said?

I know the heads/combustion chambers are the same I just put a set of heads from a 00 RR 4.0 on an 03 D2 4.6 same head casting #'s and runs perfect.

I may start a thread on that but it may have been beat to death already?

 

But Zack, isn't it the 4.6 blocks that are are the weak link? I'm with you on the 4.0 engines being more reliable but isn't that because the blocks are better.
I don't think the 4.6 fail more because it's a 4.6 but because the manufacturing and quality control got **** poor around that time and the 4.6 blocks were/are sh*t.

If I am wrong let me know.

 

could you even order a 4.6 in a 02 NAS discovery?

 

Correct, that is what I was referring to. The tooling was TOO many decades old, worn out.

However, I also believe that engine was most reliable in it's 3.5 state, be it because of the tooling then, or the lower displacement I'm not sure.

No, the 4.6 wasn't available in D2s until 2003, and it was the only option, just like the 99-02 only had the 4.0.

 

strange; why would order an emission deal from a later year and stick it on the truck.

Unless the truck was clipped in the front and the 4.6 emission decal was all that the body shop could get at the time.

fyi. if it has a 4.0 crank then its a 4.0

 

That will tell you what it should have but the engine number will tell you what it has now (on the left hand cylinder bank as viewed from inside the vehicle). That's how I found out that my 4L D2 is actually a 4.6L

Rover V8 Engine Numbers

 

Numbers on deck of LH bank of block:
CR9.35:1 56D63038A
First part of that is probably compression ratio. The second # I thought was the engine number but, unless #s that Rover V8 engine link are in progressive sequences, I didn't see a match.

Looks like it was once sleeved on one cylinder (top hat).

4.0 on crank (as previously mentioned)