composite head gaskets
Discussion
Don't be so sure the HG's aren't composite already 
Tricky to tell as you don't list any car in your profile.
The more usual question is likely to be tin / composite valley gasket, - answer being I'd say good comp & do your own port matching.
V8D keep some very nice gaskets, have a chat with them to get all that you want.
Tricky to tell as you don't list any car in your profile.The more usual question is likely to be tin / composite valley gasket, - answer being I'd say good comp & do your own port matching.
V8D keep some very nice gaskets, have a chat with them to get all that you want.
They'll be composite on a 4.3, but likely with copper fire rings and the heads o-ringed.
Some skim the rings off, or use std composite gaskets with the rings or even solid copper versions. The copper ringed composites TVR used were sourced from the US and not available anymore AIUI from Dom. A mate can get composite gaskets fitted with copper rings but it was bloomin expensive (like £10 a pot IIRC)
Some skim the rings off, or use std composite gaskets with the rings or even solid copper versions. The copper ringed composites TVR used were sourced from the US and not available anymore AIUI from Dom. A mate can get composite gaskets fitted with copper rings but it was bloomin expensive (like £10 a pot IIRC)
Separate copper fire rings are popular in the bike world, at least they were on big tuned air-cooled fours... never had much success with them to be honest. Either the rings would hold the head very slighly proud of the composite surround (with oil leakage issues), or the rings wouldn't quite clamp properly due to being slightly under thickness so that chamber blow-by was the result (often into the cam chain gallery, neatly pressurising the sump and blowing your engine oil out the breathers when the ring eventually failed entirely). Much rather have a one piece gasket with an integral crushable sealing ring.... or an entire annealed copper gasket if silly high compression is to be used (just put up with oil finding its way to the exterior).
I think ill stick with the slightly thicker composite if thats what tvr used originally. Surely using something the same thickness will keep manifolds lined up and keep the pre loads something like the same or did tvr not go to the lengths of matching everything up and checking pre loads.
Quinny said:
WokingWedger said:
How much thicker are the composite gaskets ? Enough to require re-shiming of the valve gear ?
Pre load should be checked no matter what type of gasket used
Are you shimming because the block/head/gasket/rocker-pedestals have moved or the rocker arm cups / pushrod / follower / cam base circle has moved?....
Logical analysis of cause & effect is required - as supplied new by TVR & LR all parts fit and result in acceptable preload without the need for shimming?
Logical analysis of cause & effect is required - as supplied new by TVR & LR all parts fit and result in acceptable preload without the need for shimming?
spend said:
Are you shimming because the block/head/gasket/rocker-pedestals have moved or the rocker arm cups / pushrod / follower / cam base circle has moved?....
Logical analysis of cause & effect is required - as supplied new by TVR & LR all parts fit and result in acceptable preload without the need for shimming?
Sorry to OP, I didnt mean to take over thread, but if changing head gasket it could be of interst any way.Logical analysis of cause & effect is required - as supplied new by TVR & LR all parts fit and result in acceptable preload without the need for shimming?
I had a partial rebuild done, Cam,followers, cam brgs,big ends, mains,timing chain, sprockets, oil pump etc, but no head work. Engine all nice and quiet.
A few month later a head gasket blew. Same garage couldnt/wouldnt fit me in so had new head gaskets fitted else where. After new head gasket fitted there is now a clatter from the followers on the over run. I was told this was normal due to reduced oil pressure when the engine is slowing down. I asked the garage if they re-shimed and was told they put back what ever was already there. Hence my question 'is changing a head gasket suficient disturbance to need re shiming'?
Quinny said:
I'd say yes....
In theory it should all go back the same as it came off, but the reallity is it never does....
I eould check pre-load everytime I disturbed anything at the top end....To be honest especially after a HG failure so soon after a new one was fitted.....
For example why did it fail?? Was it just bad luck or did the original garage not torque it down correctly?
If it was because of the second reason, then there will definitly be a difference in the amount of pre-load...
The excuse of low oil pressure causing a rattle on over run doesn't wash....
Oil pressure is at its lowest on tickover with a warm engine.... Does it rattle then?
+1 In theory it should all go back the same as it came off, but the reallity is it never does....
I eould check pre-load everytime I disturbed anything at the top end....To be honest especially after a HG failure so soon after a new one was fitted.....
For example why did it fail?? Was it just bad luck or did the original garage not torque it down correctly?
If it was because of the second reason, then there will definitly be a difference in the amount of pre-load...
The excuse of low oil pressure causing a rattle on over run doesn't wash....
Oil pressure is at its lowest on tickover with a warm engine.... Does it rattle then?
Also, When I had rattle on overrun it turned out to be because the valve stem tops were at differing heights so the preload was impossible to get right over all 16.Quinny said:
I'd say yes....
In theory it should all go back the same as it came off, but the reallity is it never does....
I eould check pre-load everytime I disturbed anything at the top end....To be honest especially after a HG failure so soon after a new one was fitted.....
For example why did it fail?? Was it just bad luck or did the original garage not torque it down correctly?
If it was because of the second reason, then there will definitly be a difference in the amount of pre-load...
The excuse of low oil pressure causing a rattle on over run doesn't wash....
Oil pressure is at its lowest on tickover with a warm engine.... Does it rattle then?
Head gasket wasnt touched on the partial rebuild, and was probably already failing.In theory it should all go back the same as it came off, but the reallity is it never does....
I eould check pre-load everytime I disturbed anything at the top end....To be honest especially after a HG failure so soon after a new one was fitted.....
For example why did it fail?? Was it just bad luck or did the original garage not torque it down correctly?
If it was because of the second reason, then there will definitly be a difference in the amount of pre-load...
The excuse of low oil pressure causing a rattle on over run doesn't wash....
Oil pressure is at its lowest on tickover with a warm engine.... Does it rattle then?
It dosnt rattle at tick over or at any constant revs, only on the over run
WokingWedger said:
..if changing head gasket it could be of interst any way.
I think you need to be very clear what you mean by changing head gasket? A different material / thickness or like for like? A dimension change affects the valve train geometry, if it's the same gasket then any dimensions changes are down to wear / tear.Unequal valve stem heights are kind of a concern, I can't really understand how it should happen apart from bad rebuilding, once the valve seating is cleaned up.
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