Tappets tapping badly
Discussion
Boosted LS1 said:
Copper gaskets are crap imo. Why did your composites fail?
My head gasket was renewed 6000 miles ago when I purchased the car and had a fair amount of work done on the engine. Bought the gasket from the Vauxhall club of which I am a member. Apparently the gasket failed in two areas burning out between cylinders one/two + five/six.Plenty of comments regarding early head gasket failure from use of composite gaskets are being heard via the VSSC. Enough comments to raise concerns that the material used is not adequate for the job, in other words burning through. Clearly the composite is not as good as the old asbestos.
It may well depend on who has made the gaskets and from what materials. Some folk run sheet copper head gaskets which have to be annealed to work properly. Copper composite gaskets do not seem to be as good since asbestos was banned and even then they worked best soaked in oil overnight (or whatever fluid was recommended). Copper composite gaskets have to be retorqued or they are very liable to fail( so I suppose there must be some settlement as has been suggested). The Payen composite gaskets we use we do not retorque we just use them as single torque gaskets. Heads and blocks do tend to warp a little and the gasket can take up some of these imperfections. Maybe the composite used on the VX was not very forgiving, especially as the Club members mention a fair fail rate!
If the valve clearances were steady before the head gasket was changed I would worry as to why the clearances are changing after head fit. It would be worth ensuring the oil supply is still correct. We have come across a fair few instances of wrong rocker shafts used on A series engines, the small bore and large bore ones used a different rocker post to supply the shaft so sometimes wrong posts and wrong shafts are fitted which can cause lack of oil and rapid wear making the engines very clattery. Most new shafts have two oil holes so they fit either block size but care has to be exercised that head/post/shaft line up!
Peter
If the valve clearances were steady before the head gasket was changed I would worry as to why the clearances are changing after head fit. It would be worth ensuring the oil supply is still correct. We have come across a fair few instances of wrong rocker shafts used on A series engines, the small bore and large bore ones used a different rocker post to supply the shaft so sometimes wrong posts and wrong shafts are fitted which can cause lack of oil and rapid wear making the engines very clattery. Most new shafts have two oil holes so they fit either block size but care has to be exercised that head/post/shaft line up!
Peter
crankedup said:
Why? I understand they are used in competition engines such as drag cars working under extreme conditions.
A drag cars nothing like a road car. It has perfectly machined decks and only has to make one run. A solid fire ring may be needed. For road cars a composite gasket will grip to the head and tolerate any imperfections on a 'normal' engine. The fire ring should seal the cylinder. If it doesn't then either there's detonation, excessive cylinder temps or pressures, incorrect bolt torque or head lift. None of these are the fault of the gasket. If the gaskets leaking from an oil way or coolant gallery then yes, the gasket could be at fault.I've always used composits on turbocharged cosworth 24v's and never had an issue under 20 psi which is when the heads will lift.
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