cylinder liner height .
Discussion
Does anyone know how far above or below the top of the cylinder liners should be compared to the surrounding engine block. I have just fitted new liners and want to check this dimension. I presume they should be about 2 to 4 thou higher than the engine block face so that a good clamping pressure is achieved when the heads are torqued down. engine is a 4.5 AJP.
I've measured mine carefully and without any silicon sealer around the base or the liners being clamped down they are all 4 thou LOWER than the surrounding engine block face. The gap is consistent across both banks cylinders 1 to 8. I would have thought a 2thou above the block height would have been ideal?
when I fitted new liners in my 4.2 I spoke to one of the chaps at dulfords, his advice was to rifit with the silicon around the bottom gasket, gently tap down so that the tops were just proud of the block face, then cover with a piece of thick plywood with a reasonably heavy weight on the top, and leave overnight.
once the heads are later torqued down, done gradually to the correct sequence, the liners will then bed in nicely, compressing the silicon around the gasket at the bottom of the liners, so no nasty water leaks later on.
make sure you are using the correct rtv silicon, oil resistant ect.
once the heads are later torqued down, done gradually to the correct sequence, the liners will then bed in nicely, compressing the silicon around the gasket at the bottom of the liners, so no nasty water leaks later on.
make sure you are using the correct rtv silicon, oil resistant ect.
I had to have my 4.2 rebuilt last spring, because it was overheating. Eventually, they tracked the problem down.
He said that the liner should be 5 thou above the surface of the block, to make sure the gasket rings seal properly. Mine had been rebuilt with the liners slightly below the block (about 7 though, so the gasket couldn't seal. I can't remember now if it should have been 7 though above and mine was 5 thou below - I remember the difference was 12 thou.
Early blocks had a 12 thou shim (the exact thickness I needed!) underneath the liner to lift it. Later blocks didn't. Although mine was a later engine no, it still needed the shims. He eventually tracked a set down - the last set available, he said. They went missing in the post for 2 weeks so that held up the rebuild as well - the only alternative then was a new block at over £600 plus the full rebuild cost.
He said that the liner should be 5 thou above the surface of the block, to make sure the gasket rings seal properly. Mine had been rebuilt with the liners slightly below the block (about 7 though, so the gasket couldn't seal. I can't remember now if it should have been 7 though above and mine was 5 thou below - I remember the difference was 12 thou.
Early blocks had a 12 thou shim (the exact thickness I needed!) underneath the liner to lift it. Later blocks didn't. Although mine was a later engine no, it still needed the shims. He eventually tracked a set down - the last set available, he said. They went missing in the post for 2 weeks so that held up the rebuild as well - the only alternative then was a new block at over £600 plus the full rebuild cost.
According to TVR power who assembled the original engines the liners should be 3 to 4 thou above the block face. Much more than that then you can suffer distortion of the components when yon torque down the head any less then you may not have sufficient crush on the fire rings to form a reliable seal.
Mine are 4 thou below. I intend skimming the top of the block to create a 3 thou above block measurement.
Mine are 4 thou below. I intend skimming the top of the block to create a 3 thou above block measurement.
According to TVR power who assembled the original engines the liners should be 3 to 4 thou above the block face. Much more than that then you can suffer distortion of the components when yon torque down the head any less then you may not have sufficient crush on the fire rings to form a reliable seal.
Mine are 4 thou below. I intend skimming the top of the block to create a 3 thou above block measurement.
Mine are 4 thou below. I intend skimming the top of the block to create a 3 thou above block measurement.
If youre going to run with the liners at 4 thou down then make sure you've got enough piston crown to head face clearance for full revs. get the plastiguage out and check as you're effectively running with the pistons 8thou closer to the head face than std (assuming the clearance would have been right with a 4thou protrusion). production standards being what they are you might find some pistons getting close to the head.
Edited by Alan Kee on Friday 7th January 20:48
I have clamped the liners in place and measured the clearance with both the old and new liners. Each time it is 4 thou. By skimming the block down to get a 4 thou protrusion I should get the recomended clamping pressure on the gasket. the liner height will not have changed although I fully appreciate that the head will be clamping the gasket much tighter than before. I am aiming for about a 30thou squish clearance on my engine but will check this very carefully when assembling.
spongy said:
I may be wrong bud
but i would really try not to skim block.In my opinion this could lead to problems later on,you may well get a result this time but what happens in the future if god forbid you need to skim heads etc.
I can see what you mean but I am only correcting a faulty dimesion in the first place. I know the cylinder liners are not at fault as both the original factory ones and the new power ones give me the same 4thou clearance. I would presume that either the liner seating face or the block height was machined incorrectly by TVR in the first place. but i would really try not to skim block.In my opinion this could lead to problems later on,you may well get a result this time but what happens in the future if god forbid you need to skim heads etc.Would gather engine had a major problem to cause this rebuild,but as regards to comments about water problms due to liners this i cant see.the head gasket should stop water getting near bores long before liner edge
i can see if liners sat to high this could cause head not to seat properly.from experience the head normally has water issues if its warped or the gaskets simply fecked.If the engine has run well for this long on its original build then i would still not skim block.Sure if you are going to enter in a race series and need max engine effiency ect then yes i can see slight compression gains.Please i may be missing the point but you have bores lined due to bore wear,or maybee damage.
i can see if liners sat to high this could cause head not to seat properly.from experience the head normally has water issues if its warped or the gaskets simply fecked.If the engine has run well for this long on its original build then i would still not skim block.Sure if you are going to enter in a race series and need max engine effiency ect then yes i can see slight compression gains.Please i may be missing the point but you have bores lined due to bore wear,or maybee damage.Just another point to think about bud is that in one above view it is recommended that you sit a ply board over top block with a weight on it,now this wound imply that the surface was or is never that flat from factory due to the ply taking top proflile when left overnight.in this case if top of block was say concave a gnats cock then your heads would surely have slightly taken that profileIf you now decide to skim block so its 100% you may get an issue if your using original heads as they will still be to old block spec.May be wrong but just think its food for thought
If you now decide to skim block so its 100% you may get an issue if your using original heads as they will still be to old block spec.May be wrong but just think its food for thoughtspongy said:
Please i may be missing the point but you have bores lined due to bore wear,or maybee damage.
That would be true of dry liners, but the point you're maybe missing is that the AJP8 engine has wet liners - the seal between the liner and the head is critical because that's all that keeps compression gasses in, and water out. spongy said:
Just another point to think about bud is that in one above view it is recommended that you sit a ply board over top block with a weight on it,now this wound imply that the surface was or is never that flat from factory due to the ply taking top proflile when left overnight.in this case if top of block was say concave a gnats cock then your heads would surely have slightly taken that profileIf you now decide to skim block so its 100% you may get an issue if your using original heads as they will still be to old block spec.May be wrong but just think its food for thought
If you now decide to skim block so its 100% you may get an issue if your using original heads as they will still be to old block spec.May be wrong but just think its food for thought
the idea idea of putting the wood with a weight on top overnight is so that you leave the silicon to go off overnight, its very important to form a good 100% seal between the bottom of the liners and the metal gasket and block to stop water from getting into the sump and oil into water ect, if you were to put the head on straight away the silicon may be to soft and come out of the mating face to easy, if left to go off overnight, then fit the heads and tighten down gradually then a good seal will be made pushing the liners home that last coulpe of thou.if in any doubt contact dom tvr power, jason str8six, andy at apm or dulfords for advice.
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