1999 Thor engine big ends

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boycie

boycie

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Silver end Braintree ESSEX
Hi I have been looking at Saints very complete post on how to change the big end and main bearings on a Gems engined p38 with the engine still in the car,can anyone think of a reason why the same cannot be done with the Thor engined p38 ?.
 
I know this was 2 months ago but having recently changed big ends and mains with the engine out I'd say don't do it. Although the cranks don't wear assuming coolant isn't entering the oil they do get rough and need polishing. If they or just one knocks the crank is gone BUT mine knocked for years! When you remove the sump and pickup pipe you lose prime to the pump.....the restart can trash the bearing. Engines are precision things even Rover v8s....do it properly or leave it!
Even better fit a new front cover and oil pump probably more effective than new bearings( if it survives( reprime and start!)
John
 
Technically of course this is true. Actually it took me several hours and many rechecks to check the journal sizes were all within tolerance after polishing plastigauge works well on the mains but not the big ends . (One imperial size in rave is wrong btw!) I'd guess another hour or two to actually torque the things up.
If it's high mileage or knocking it's just a sticking plaster at best. My crank was ruined on one journal after the top hat liners at the rear of the engine sunk 4 thou. This caused a minor leak into the cylinder and past the Piston into the oil. Very small amounts of coolant. If you change your oil every 3000 you wouldn't notice but it really kills bearings. Btw yes top hat liners definitely fail if they aren't put in properly. They sink when the engines hot.
Not discouraging anyone from trying though. If the vehicle has been looked after the cranks are tough as owt. My replacement was from a Thor with an unknown mileage and after polishing was on or just over bottom tolerance.
 
johnnyb70 said:
Technically of course this is true. Actually it took me several hours and many rechecks to check the journal sizes were all within tolerance after polishing plastigauge works well on the mains but not the big ends . (One imperial size in rave is wrong btw!) I'd guess another hour or two to actually torque the things up.
If it's high mileage or knocking it's just a sticking plaster at best. My crank was ruined on one journal after the top hat liners at the rear of the engine sunk 4 thou. This caused a minor leak into the cylinder and past the Piston into the oil. Very small amounts of coolant. If you change your oil every 3000 you wouldn't notice but it really kills bearings. Btw yes top hat liners definitely fail if they aren't put in properly. They sink when the engines hot.
Not discouraging anyone from trying though. If the vehicle has been looked after the cranks are tough as owt. My replacement was from a Thor with an unknown mileage and after polishing was on or just over bottom tolerance.
Click to expand...

If it is knocking doing it is a waste of time. Your leak was due to a cracked block releasing the liner. Under normal circumstances the coolant does not come into contact with the liner. Slipped liners due to cracked blocks are a result of Land rover not increasing the block wall thickness when they increased the cylinder bore of the 3.5 to get the 4.0 litre or more correctly the 3.9.
 
Mine was due to wards engineering not pushing and keeping the top hat liners onto the rebate. Acr in deeside who skimmed my block again(very highly recommended) said they bore to the exact thickness of the new liners flange then press in any discrepancy is immediately obvious and put right. They don't even have to deck the block! On race engines they even leave the flange 1 or 2 thou proud. Roland immediately knew what had happened as he'd seen it a few times(thank God)
Search internet forums nobody ever mentions top hat liners sinking on Rover v8. Most suggest it's fit and forget. Not so. Top hat liners don't cure a cracked block they just stop the coolant escaping when the tops sealed with the head gasket. Pressure test a top hat block and air will pee out at the original cracked liners at the top. If these sink more than 1 or 2 thou it'll lose coolant.
 
johnnyb70 said:
Mine was due to wards engineering not pushing and keeping the top hat liners onto the rebate. Acr in deeside who skimmed my block again(very highly recommended) said they bore to the exact thickness of the new liners flange then press in any discrepancy is immediately obvious and put right. They don't even have to deck the block! On race engines they even leave the flange 1 or 2 thou proud. Roland immediately knew what had happened as he'd seen it a few times(thank God)
Search internet forums nobody ever mentions top hat liners sinking on Rover v8. Most suggest it's fit and forget. Not so. Top hat liners don't cure a cracked block they just stop the coolant escaping when the tops sealed with the head gasket. Pressure test a top hat block and air will pee out at the original cracked liners at the top. If these sink more than 1 or 2 thou it'll lose coolant.
Click to expand...

Top hat liners should never sink if they are fitted correctly. That is the whole point of fitting them, the flange is trapped in the rebate between block and head locking them in place.
 
Top hat liners are difficult to fit the traditional way tbh. The rebates are machined shallower than the flanges in the liner. Most old boring machines have no depth scale btw. The flanges are cooled in nitrogen and sometimes the block heated. When the liner and block are mated the differential shrinkage can tend to leave the liner a few thou off the rebate. Ideally a method to force the liners down as it cools should happen. A plate in the head bolts or bumping down when nearly cool. Loctite silicone is used at the bottom btw. Finally the block is faced. Wards linered many many blocks for individuals and companies btw. If your spending £1000+ and you want a coolant tight block use a proper company (acr or Turner's) or better ask how they do it. When you go back and say my block is leaking they will not be interested. Wards no longer do v8s btw although the guy is very pleasant he's not daft!
 
johnnyb70 said:
Top hat liners are difficult to fit the traditional way tbh. The rebates are machined shallower than the flanges in the liner. Most old boring machines have no depth scale btw. The flanges are cooled in nitrogen and sometimes the block heated. When the liner and block are mated the differential shrinkage can tend to leave the liner a few thou off the rebate. Ideally a method to force the liners down as it cools should happen. A plate in the head bolts or bumping down when nearly cool. Loctite silicone is used at the bottom btw. Finally the block is faced. Wards linered many many blocks for individuals and companies btw. If your spending £1000+ and you want a coolant tight block use a proper company (acr or Turner's) or better ask how they do it. When you go back and say my block is leaking they will not be interested. Wards no longer do v8s btw although the guy is very pleasant he's not daft!
Click to expand...

Yeah i know how they are fitted. As said fitted properly there should never be a problem.
 
Sorry wammers not preaching or nowt it's just for the record really. I tend to read forums like a religious text. One snippet of info can save months or weeks of problems. Your posts are always spot on!
Jb
 
johnnyb70 said:
Sorry wammers not preaching or nowt it's just for the record really. I tend to read forums like a religious text. One snippet of info can save months or weeks of problems. Your posts are always spot on!
Jb
Click to expand...

Problem with that is most if not all religious texts are bullshit. Some need to be careful what they believe. I just dismiss them knowing differently, but some think articles written by the mostly unknowing are gospel truth. Then quote them as fact in places like this. ;);)
 
Reading all this tech. discussion, plus painful memories of a 3.9 that slipped a liner, prompts me to question LR's decision to bore the old 3.5 block instead of stroking it - as they eventually did with the 4.2.
 
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