Building up my 4.6 at the moment,I am giving some thought to ways to minimize the chances of having a stock liner drop.No way would I consider swapping to top hat liners,cost over here would be astronomical.Was thinking of a small (Alloy)tack weld in 2 places on the block at the base of the liners to create a step to stop them dropping.With the head/fire ring clamped on top and this down the bottom I cant see them moving.Of course I could be wrong.......Any thoughts?
Doug
4.6 liners......locking them in place.
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CastleMGBV8
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Doug,
I can't tell you whether this is feasable but be aware that the skirt of a 4.6 piston protrudes approx 7mm below the bottom of the liner at bottom dead centre!
I've always wondered if the use of composite gaskets on the later engines has anything to do with liner displacement as the 3.9 engines with the same bore,but using the thinner tin gaskets did not seem to suffer from this problem as commonly as the later engines.
Liner displacement is said to be caused by combustion pressure, therefore the gases must be passing the initial part of the gasket to allow pressure on top of the liner to push it down. possibly the sealing ring on the composites is not as efficient due to the compressability of the composite gaskets, just a thought anyone care to comment?
Kevin.
I can't tell you whether this is feasable but be aware that the skirt of a 4.6 piston protrudes approx 7mm below the bottom of the liner at bottom dead centre!
I've always wondered if the use of composite gaskets on the later engines has anything to do with liner displacement as the 3.9 engines with the same bore,but using the thinner tin gaskets did not seem to suffer from this problem as commonly as the later engines.
Liner displacement is said to be caused by combustion pressure, therefore the gases must be passing the initial part of the gasket to allow pressure on top of the liner to push it down. possibly the sealing ring on the composites is not as efficient due to the compressability of the composite gaskets, just a thought anyone care to comment?
Kevin.
The sealing ring whether it is comp or tin gasket is no where near the top of the liner. Its only when you fit the top hat liners that you get a seal between gasket and liner. The 4.6 block is also re-designed as well, if you pop a core plug you can see the difference so this might be why they fail more. There is also a theory that the stretch bolts can cause it as they put more stress on the block. And of course the oldest theory that its local overheating due to lean mixtures which in theory could be worse on the 4.0 4.6 as they are more modern with stricter emission controls.CastleMGBV8 wrote:
Liner displacement is said to be caused by combustion pressure, therefore the gases must be passing the initial part of the gasket to allow pressure on top of the liner to push it down. possibly the sealing ring on the composites is not as efficient due to the compressability of the composite gaskets, just a thought anyone care to comment?
Kevin.
To the original question, I always thought that a slipped liner was a symptom and not a cause. When the alloy wall behind the liner cracks grip is lost and the liner drops. If that's the case then stopping the liner from dropping isn't going to help anything as the alloy can still be cracked behind it and the same problems will occur.
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CastleMGBV8
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Marki,
Thanks for putting me straight on that, but am I correct that the 3.9 blocks are more reliable regarding liner stability?
The main reason I am interested is that I was thinking of boring a 3.9/4,2 block out to 94.89mm to take a Chevy 305 piston and am wondering if it's going to cause problems.
The reason for this is I have a pair of Buick 300 heads with 54cc chambers and need to use a flat top piston to restore compression.
I have acces to a 4.2 crank and will need the 5.85" rods to get the pistons to the top of the bores, the engine capacity will then be 4.3L which should be large enough to justify using the Buick heads.
Kevin.
Thanks for putting me straight on that, but am I correct that the 3.9 blocks are more reliable regarding liner stability?
The main reason I am interested is that I was thinking of boring a 3.9/4,2 block out to 94.89mm to take a Chevy 305 piston and am wondering if it's going to cause problems.
The reason for this is I have a pair of Buick 300 heads with 54cc chambers and need to use a flat top piston to restore compression.
I have acces to a 4.2 crank and will need the 5.85" rods to get the pistons to the top of the bores, the engine capacity will then be 4.3L which should be large enough to justify using the Buick heads.
Kevin.
I cant say for sure whether the 3.9 is more reliable than the 4.6 but if this forum is anything to go by then yes it seems to be. I can only remember of maybe 2 people here having a cracked 3.9 but it seems to be every month or so someone has a duff 4.6. It might not have went in their use as they might have bought it like that and asking advice on top hats or something but failed they are.
