v8kenny
Active Member
4.0 is no better on fuel consumption and in some cases can actually be worse - stick with a 4.6 and enjoy the extra power for no loss of consumption !
Oh and when the horror stories start flooding in about "porous" blocks ignore it - it's all bollocks as they both use the same block
Extra capacity comes from a longer stroke
No such thing as a porous block anyway - it's metal FFS - not cardboard
Oh and when the horror stories start flooding in about "porous" blocks ignore it - it's all bollocks as they both use the same block
Extra capacity comes from a longer stroke
No such thing as a porous block anyway - it's metal FFS - not cardboard
Pikey
Dummy Ejection Facilitator..
yeh someone who thinks the same way as me. The problem is actually slipping liners allowing gases & coolant to get between the liners and the cylinder bores.
Mike Robinson
New Member
Will have to disagree with the statement about slipping liners on the V8s.
The liners are not wet liners - they do not touch the water jacket inside the block and they certainly don't slip.
SO re there being no such thing as a porous block, what is it that all these engines are experiencing then? Don't get me wrong I am not disagreeing with you, just want to know what your theory is.
Bonnieboy, I recon it is swings and roundabouts having had both. I remember when they were still in production a few different salesmen saying the 4.0 was smoother but i dont really notice it. Think you get more oomph from the 4.6 dont think there is much in the fuel consumption really. Dont think the 4.6 is any more prone to naughties than the 4.0 as has already been stated the extra cc's come from the stroke being longer not the cylinders being wider. Would put my 2 pence worth of advice in by saying i recon its more down to the actual car you find condition wise, as to what is best. and of course the 4.6 tends to have more toys... (what do you mean more to go wrong?) ...
Mike Robinson
New Member
We have reconditioned dozens of these engines, especially ones that have suffered with 'Porous Block Syndrome'.
On one occasion after the liners were removed (we fit 'Top Hat' Liners to all our recons) we could actually see a hairline crack in the bore of the block structure.
On a 'Porous Block' there is definitely combustion gas entering the cooling system when the engine is running and coolant getting into the combustion chamber when the engine is not running - normally overnight.
With the original parallel liners the fire ring on the head gasket is on the outside of the cylinder liner, any degradation in the block structure can allow combustion gas to go down the outside of the liner and the only way it can get into the coolant is through the block casting!
On engines with the Flanged aka 'Top Hat' Liners the fire ring on the head gasket actually sits on the top surface of the liner meaning combustion gases cannot get down the outside of the liner.
Ah got you, so it is due to a crack not the whole thing being a honeycombe? Sorry if seem slow, just have never understood this. So there is a hairline crack in the block rather than lots of holes? Is that due to many different things such as overheating/buring too hot/bad engine mapping or more likely than not, lack of quality control in the factory? Or is it a case by case situation? Cheers for the reply though. Light is dawning.
Mike Robinson
New Member
TBH we have only actually seen one crack and that stood out like a sore thumb.
On cold pressure test the coolant void in the block is pressurised with air and the whole block submerged in fluid and you can see air bubbles escaping just like when you check a push bike inner tube.
Just like this
The rear cylinders seem to be the worst although all cylinders do have problems.
It is possibly metal fatigue caused by the constant heating and cooling of the block structure - the rear cylinder on each bank runs slightly hotter than the other cylinders due to their position in the cooling system and them being further away from any cooling air entering the engine bay.
All my opinion of course
Mike Robinson
New Member
The 'normal' cracks are too small to be seen with the naked eye although some are easily visible using a Penetrant Flaw Detection (PFD) kit such as the Ardrox kit.
More likely to be IF rather than WHEN.
V12
New Member
Sorry, but I can't agree with you about liners slipping. We are reconditioning a lot of blocks and often liners are moved down into the bore, a specially in leaking cylinders. Obviously liners are not a part of water jacket, but hairline crack combined with dropped liner means trouble
The porosity of block is strictly connected with tendancy to cracking- porous casting is not so strenght as it should be.
Below block repaired in Poland:
and CNC centre we use:
