Can I use a 4l block to repair 4.6?

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S

sandyt

Well-Known Member
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Wraysbury Nr Heathrow
Gents I have not one but two slipped liners so either send it away to have top hats done or I can get a 4 l cheap can I use the block from the 4 and put all my its on from the 4.6 Sensors crank the lot or will it not work
 
How much is cheap?

Rimmer Bros list a new block (Part: LCF000280 (£3192.51) no longer available) as the same part number for 4.0 and 4.6 so I think they probably are.

I've read a few times that the extra 600cc was gained through lengthening the stroke so you'll need to change everything over......

I'm interested to hear how you get on with this.
 
MrGorsky said:
How much is cheap?

Rimmer Bros list a new block (Part: LCF000280 (£3192.51) no longer available) as the same part number for 4.0 and 4.6 so I think they probably are.

I've read a few times that the extra 600cc was gained through lengthening the stroke so you'll need to change everything over......

I'm interested to hear how you get on with this.
Click to expand...
As far as I know, they just bored them to get the extra capacity which is why the blocks are weak. Liner thickness may also be different. If they had stroked the 3.5 there would have been far fewer problems with slipped liners & cracked blocks but the extra torque would probably have been too much for the box & the diffs:rolleyes:

OK, just checked, 3.5, 3.9 & 4.0 share the same stroke but different bores, the 4.6 has the same bore as the 4.0 but a longer stroke.
 
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RAVE states the bore of the 4.0 and 4.6 to be 94 - 94.04mm
Stroke of the 4.0 is 71.04 - 71.20mm
Stroke of the 4.6 is 81.92 - 82.08mm

RPi engineering also state on their site that the 3.9, 4.2, 4.0, and 4.6 are all the same 94mm bore. Just with different stroke lengths, the later engines getting 'big journal' cranks.

The wikipedia page says the same. I think it'll work Sandy.

I've read somewhere that the 4.6 engines got the better castings than the 4.0 ones. Probably rumour from snobbish 4.6 owners, but if the cost of 8 new top hats is not that much more than the 4.0 block I'd go for that. At least you know it's done then, once and for all.
 
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MrGorsky said:
I've found a reference to the 4.6 blocks being thicker...

http://www.landyzone.co.uk/lz/attachment.php?attachmentid=41150&stc=1&d=1359649619

Now, this might not be true, but next time you're in the garage, can you see any red or yellow paint in your vee?
Click to expand...
If the 4.0 had the thinnest block and the 4.6 shares the same bore as the 4.0, I don't see how the 4.6 can have a thicker block.
The failure rate of the 4.0 & 4.6 blocks with liner slip, cracks etc suggests that they share the same thin wall block.
 
The suggestion is that the castings varied in quality so much, that they checked them all as they came out and gave the ones with the more uniform wall thicknesses to the 4.6 litre engines.

The picture above is a bit mis-leading, it only shows the minimum wall thickness found in any casting. If you have a thin wall at one side of your cylinder then you have a thicker wall at the other side.

LR knew the blocks could crack where the casting was very thin, (they called it going porous) causing slipped liners, and so (I suppose) they tried to get the best blocks for the bigger torque of the 4.6 thinking it would need the extra (or more uniform) strength.

I was reading on a TVR forum (they suffer slipped liners like the rest of us) that RR engines suffer worse than any other car that the V8 was fitted to because the fuel map is different.

LR needed to keep the fuel consumption down as best they could and so fuelled lean at cruising throttle openings. This causes the cylinder temp to be higher (?) and so the chance of a slipped liner is higher. I didn't quite understand all of it.

They went on to say the chipping the V8 (Thunderchip or something) can correct this fuel map, and the instance of slipped liners is lessened.

Either way it costs lots of money!
 
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MrGorsky said:
The suggestion is that the castings varied in quality so much, that they checked them all as they came out and gave the ones with the more uniform wall thicknesses to the 4.6 litre engines.

The picture above is a bit mis-leading, it only shows the minimum wall thickness found in any casting. If you have a thin wall at one side of your cylinder then you have a thicker wall at the other side.

LR knew the blocks could crack where the casting was very thin, (they called it going porous) causing slipped liners, and so (I suppose) they tried to get the best blocks for the bigger torque of the 4.6 thinking it would need the extra (or more uniform) strength.

I was reading on a TVR forum (they suffer slipped liners like the rest of us) that RR engines suffer worse than any other car that the V8 was fitted to because the fuel map is different.

LR needed to keep the fuel consumption down as best they could and so fuelled lean at cruising throttle openings. This causes the cylinder temp to be higher (?) and so the chance of a slipped liner is higher. I didn't quite understand all of it.

They went on to say the chipping the V8 (Thunderchip or something) can correct this fuel map, and the instance of slipped liners is lessened.

Either way it costs lots of money!
Click to expand...

Buick built over 300,000 cars with this engine (plus it was also used by Pontiac and Oldsmobile), they upped the capacity by increasing the stroke and seem to have had no problems.
LR chose the cheap option to increase capacity and perhaps the Americans had better quality control of the casting process.
 
Dr_evil said:
Bet it drinks though! :jaw:




May be a good use for that spare SD1 block I now have :p
Click to expand...

Probably goes bang pretty quick too but as it was used for racing they were probably not bothered.
There is an iron block version of the engine, might be worth sourcing iron blocks to replace the alloy ones in the RR, no more slipped liners:)
 
Datatek said:
Probably goes bang pretty quick too but as it was used for racing they were probably not bothered.
There is an iron block version of the engine, might be worth sourcing iron blocks to replace the alloy ones in the RR, no more slipped liners:)
Click to expand...

Problem is then it'd weight the same as a small hemi! All that over the front axle may detract from the already wallowing steering ;)
 
Datatek said:
If the 4.0 had the thinnest block and the 4.6 shares the same bore as the 4.0, I don't see how the 4.6 can have a thicker block.
The failure rate of the 4.0 & 4.6 blocks with liner slip, cracks etc suggests that they share the same thin wall block.
Click to expand...
they are the same block 4/ and 4.6 and gems and thor
 
MrGorsky said:
The suggestion is that the castings varied in quality so much, that they checked them all as they came out and gave the ones with the more uniform wall thicknesses to the 4.6 litre engines.

The picture above is a bit mis-leading, it only shows the minimum wall thickness found in any casting. If you have a thin wall at one side of your cylinder then you have a thicker wall at the other side.

LR knew the blocks could crack where the casting was very thin, (they called it going porous) causing slipped liners, and so (I suppose) they tried to get the best blocks for the bigger torque of the 4.6 thinking it would need the extra (or more uniform) strength.

I was reading on a TVR forum (they suffer slipped liners like the rest of us) that RR engines suffer worse than any other car that the V8 was fitted to because the fuel map is different.

LR needed to keep the fuel consumption down as best they could and so fuelled lean at cruising throttle openings. This causes the cylinder temp to be higher (?) and so the chance of a slipped liner is higher. I didn't quite understand all of it.

They went on to say the chipping the V8 (Thunderchip or something) can correct this fuel map, and the instance of slipped liners is lessened.

Either way it costs lots of money!
Click to expand...

Unfortunately this isn't the case. I had a TVR Chimaera and it suffered a slipped liner. It's more likely the added weight of a RR means the engines work harder.
 
i really feel for you mate,if it was me i would get the rest of the liners in your original block done.
when my engine slipped a liner i took a chance on a used engine so i could rebuild the original at my leisure,still aint got around to it and its been 2 years,maybe a job this summer maybe lol
 
stjohnsmythe said:
Unfortunately this isn't the case. I had a TVR Chimaera and it suffered a slipped liner.
Click to expand...

There are certainly lots of people on TVR forums complaining about it, so they obviously slip liners in any application.

Some people bore them out to 5.2 litres (96mm). Thickness of the casting between the cylinder and water jacket must be waffer thin at that size. I'm surprised they don't just bend in half.
 
Datatek said:
Buick built over 300,000 cars with this engine (plus it was also used by Pontiac and Oldsmobile), they upped the capacity by increasing the stroke and seem to have had no problems.
LR chose the cheap option to increase capacity and perhaps the Americans had better quality control of the casting process.
Click to expand...

Not just a matter of quality control, totally different production methods, the GM/Buick engines were gravity die-cast - around the liners, Rover engines were sand cast with the liners pressed in. The Rover engines also had a 1,000rpm higher rev ceiling which puts more stress on the engine.
 
The weak fuel map thing was cr-p peddled by people who sold chips,made no difference at all to engine life.It was easy to prove how the engine was fuelled,shame was few people bothered to monitor it,so many folk believed the story.
The engine was designed for an 87.5mm bore which is where it should have remained.At least then BL/ARG/Rover Group/Land Rover etc could have made them badly and gotten away with it.
Had Honda had a chance to buy or buy into the group there would have at least been a chance that they would have then sized up the engine and made a longer crank,with larger bore centres etc to have carried on what was a fine design....
 
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