4.6 block options

[discograham]

I have search for a couple of days on here and still can't find info on replacement options for the 4.6 block.

I have a 2004 discovery (90k miles), looking at a head gasket job and am preparing for the worst case scenario.

The one option I know of is a used engine, but I have a hard time trusting something that has already failed.

I am also looking for feedback on the claims I have read on some threads that the computer's lean fuel map causes these blocks fail. This is important to me because in the future I do not want to ruin my replacement block (or my current block if it is good).

thanks guys, I have already learned a lot from all I have read in threads over the year since I have owned my discovery.

 

[slowNstdy]

2.8L power stroke conversion

 

[Paul K]

Graham:

Do you have reason to believe your current block is shot, or are you just concerned that it will fail?

If there was an easy swap, we'd all have already done it.

Options depend on how much $ you have available!

Cheers,

Paul.

 

[ptschram]

The one option I know of is a used engine, but I have a hard time trusting something that has already failed.

Already failed?

Chances are that the reason a DII engine has failed is directly related to the cooling system, not the fuel map.

 

[R_Lefebvre]

Who said the engine runs lean? It runs at 14.7:1 just like every other engine.

 

[ptschram]

Who said the engine runs lean? It runs at 14.7:1 just like every other engine.

At perfect stoichiometry:rofl:

 

[discograham]

This is why I posted, it does not sound right to me either but I read it in a post on an old thread, it said:

Porous block is caused by micro cracks in the block caused by localized overheating in the upper cylinder due to too lean a fuel mixture as programmed in the factory fuel curves in the ECU. It happens under load conditions at slow speeds, like pulliing a trailer or steep hills with full throttle.

http://www.discoweb.org/forums/showthread.php?t=36462&highlight=pushing+coolant


I have seen info eluding to this in more that one location,but can't remember other places. One was on a site selling a new ECU promising to correct the problem. I know this is an old thread, but just wondering if there is any truth to claim.

Thanks

 

[R_Lefebvre]

At perfect stoichiometry:rofl:

What are you getting at? It does run at 14.7:1 when in closed loop.

Porous block is caused by micro cracks in the block caused by localized overheating in the upper cylinder due to too lean a fuel mixture as programmed in the factory fuel curves in the ECU. It happens under load conditions at slow speeds, like pulliing a trailer or steep hills with full throttle.

That's bullshit. If there was localized heating due to a lean mixture under load, what do you think would crack first? The aluminum block structure which has a direct connection to the water jacket, and only gets heat that first passes through the stee liners? Or the aluminum pistons, which are in direct contact with the combustion, and can only shed heat to the oil spashing underneath, or to the liners through contact?

 

[kbeefy]

What are you getting at? It does run at 14.7:1 when in closed loop.

Have you ran a wideband and watched the AFR? Most have quite a bit of buffer on the rich side. Theres way to many fluctuations and variables to run that close to damage.

 

[R_Lefebvre]

No, I haven't put my wideband on it. No need. The narrowbands tell the story. Just look at the signal dithering either side of 0.5V, that's stoich. It's not possible to pass emissions unless you're dithering at 14.7:1 in closed loop. I know, I tried it. Had to get my trackday car to pass emissions. I had it running open loop, 15:1 on the wideband, not a chance. Open loop, retuned to 14.2:1, not a chance. 14.5, nope. Had to set it to cruise at 14.7:1 closed loop with the wideband to get a pass. Just a few points either side of 14.7:1 at cruise and the NOx or CO go through the roof.

 

[discograham]

Not getting much new info yet , I thought I would try again with more specific questions.

Can a damaged block be repaired? I have read something about 'top hats' but do not know what that is.

Can you use parts from older land rovers to assemble an engine that can be installed into my 04 disco?

Are aftermarket blocks available? I have read something about blocks from D&D fab, that sound pricey though.

If I get a used engine are there precautions to take to prevent the block from cracking?


thanks again!

 

[ptschram]

Yes, blocks can be repaired. If you buy one from Mark, he will have welded any cracks before installing the liners.

Yes, any Rover V8 engine with a crank sensor can be put into your truck.

Sometimes, aftermarket blocks are available, but they'll make Mark's look affordable.

Don't let it overheat!

 

[turbodave]

^^^^ What he said...

The 'any crank sensor' bit just needs clarification though - if you find a GEMS block, I believe you will need to get the Bosch crank sensor housing fitted.


IIRC there also other little things like the mounts for the knock sensors? It is all pretty easy stuff though.

I got my top-hat block from V8Developments in the UK - because I had the 2003 funny-block with the mis-machined front cover dowels. I wanted to rid myself of all that nonsense and start with a seasoned block from when they were still making them reasonably well (my 'new' block was 1998 vintage originally)...

Going rate is $200 a sleeve for the top-hats I recall - not including additional work to repair cracks or whatever.

 

[seventyfive]

I have search for a couple of days on here and still can't find info on replacement options for the 4.6 block.

I have a 2004 discovery (90k miles), looking at a head gasket job and am preparing for the worst case scenario.

The one option I know of is a used engine, but I have a hard time trusting something that has already failed.

I am also looking for feedback on the claims I have read on some threads that the computer's lean fuel map causes these blocks fail. This is important to me because in the future I do not want to ruin my replacement block (or my current block if it is good).

thanks guys, I have already learned a lot from all I have read in threads over the year since I have owned my discovery.

if you pull heads and put pressure to the cooling jackets and you have a bad block, contact will and have him send one of his bottom ends out to his guy that shoulders the liners....that's what i would do. a four six from a p38 will bolt in fine, don't spend all that money to get something from england, save that money to replace the next thing that will fail tremendously on these pieces of shit.

NEVER EVER replace a short block with a dealer short block, get a shortie that has shouldered liners.

 

[seventyfive]

Yes, blocks can be repaired. If you buy one from Mark, he will have welded any cracks before installing the liners.

Yes, any Rover V8 engine with a crank sensor can be put into your truck.

Sometimes, aftermarket blocks are available, but they'll make Mark's look affordable.

Don't let it overheat!

does mark bore the cylinders and shoulder the liners? anyone that spends any money on a short block that doesn't have that done is dumb.

and the best thing about these pieces of shit, you don't even have to let it overheat to drop a liner.....it's recycled american v8's with some english attitude...it will fail even when it ain't supposed to just like maggie.

 

[R_Lefebvre]

At perfect stoichiometry:rofl:

So, are you going to back this up with anything?

 

[KyleT]

pourus block is not related to fuel map. slipped liners can be (its a stretch). the block porosity is becasue they were rushed through production.

 

[R_Lefebvre]

Yes, I've suspected that the porosity was not created during the product's life (erosion, stress, thermal) but during it's creation. Could be a classic casting porosity problem that somehow slipped through. Maybe it wasn't bad enough that they failed pressure test in the factory, but then the pores opened up slightly with use.

 

[ptschram]

So, are you going to back this up with anything?

The EMS is constantly trying to achieve perfect stoichiometry, thus the constantly changing outputs of the oxygen sensors and corresponding change sto injector pulse width.

As fuel changes constantly, air density changes, on and on, the 14.7 is a perfect number for a perfect world (and impossible to state as gasoline is such a widely varying mixture of compounds). Oxygen concentration in free air varies from about 19 to about 22%, that's a big variation when calculating reduction and oxidation potentials.

I do not live in a perfect world and recognize that stoichioemtry is, other than an important concept to understand, something that is rarely, if ever achieved in the real world-well, maybe hydrogen combustion, but everything else varies somewhere with less 100% efficiency..

If the engine could run always at perfect stoichiometry, we wouldn't need adaptive values, oxygen sensors, nor closed loop operation.

I'm not even going to get into calibration drifts and no means to calibrate with a primary standard.

 

[seventyfive]

Going rate is $200 a sleeve for the top-hats I recall - not including additional work to repair cracks or whatever.

the machine shop we use (blueprints motors as well) charges about 60-80 bucks per cylinder, bores the old liners out, leaves a shoulder, presses new liners in, and fly cuts the block (decking). he did all the rover heads and bottom ends when land rover/jag was still in frederick.