I have a slightly sticky No 2 exhaust valve - gives erratic emissions readings and, perhaps around once a second, a slight hiccup in the exhaust rhythm, so the head will be coming off. It's the K8 as fitted to the Rover 100.
So this topic has been a valuable read, even though I replaced the head gasket around 5 years ago (with the first generation MLS + shim); I welcome this refresher - thanks to everyone. Being in no immediate rush to do the job has given me plenty of time to fully research the project; it's surprising how much info I've been able to pick up, not least of which was discovery of the existence of the modified "carbon-break" exhaust valve.
One tip I picked up to minimise/prevent coolant loss/weepage past the head gasket after fitting is to run, at idle for half an hour with the coolant system unpressurised to allow the viton coating on an MLS gasket to soften and bond to the mating surfaces without interference from weeping coolant, especially antifreeze, which lowers the surface tension of the coolant making weepage all the more likely. I had been contemplating first running the engine dry after fitting for perhaps 30 sec to a minute and letting it cool before adding coolant. And I may well do that and then run unpressurised to give the viton coating every chance to bond cleanly.
I also noted the absence of any mention in this thread of peening the fire-ring area (if indented) prior to machining to work-harden that critical area. In the trade magazine Professional Motor Mechanic (PMM) (Feb 2010), Ultra Parts, the manufacturers of composite and MLS gaskets, state "surfaces finishes should be commercialy smooth. A mirror finish is ideal" as well as "assembly conditions must be clinical". I don't wish to rekindle the skim vs no-skim argument, but the article states "heads should be refaced as a matter of procedure. Both the block and head faces must be flat and parallel within 0.003" of flatness." They also say not to panic if minor leaks are noticed between the head and the block because the viton or silicone sealing surface has to soften under initial run-up temperatures and, if neceassary, one should repeat the run-up procedure when cold to aid the self-healing process.
As mentioned in this topic, they state the liners must stand proud of the block. The PMM article states 0.002". I've more commonly seen figures closer to 0.005", but the one thing all are agreed on is that the liner heights above the block must be the same.
Head bolts should be lightly lubricated with engine oil especially under the bolt head and the head of any washers fitted. And Ultra Parts is adamant that no sealants of any kind should be used on the head gasket. (In my ignorance 5 years ago, I used Hylomar on the MLS gasket and shim without detriment, but I won't be repeating that error this time.)
So this topic has been a valuable read, even though I replaced the head gasket around 5 years ago (with the first generation MLS + shim); I welcome this refresher - thanks to everyone. Being in no immediate rush to do the job has given me plenty of time to fully research the project; it's surprising how much info I've been able to pick up, not least of which was discovery of the existence of the modified "carbon-break" exhaust valve.
One tip I picked up to minimise/prevent coolant loss/weepage past the head gasket after fitting is to run, at idle for half an hour with the coolant system unpressurised to allow the viton coating on an MLS gasket to soften and bond to the mating surfaces without interference from weeping coolant, especially antifreeze, which lowers the surface tension of the coolant making weepage all the more likely. I had been contemplating first running the engine dry after fitting for perhaps 30 sec to a minute and letting it cool before adding coolant. And I may well do that and then run unpressurised to give the viton coating every chance to bond cleanly.
I also noted the absence of any mention in this thread of peening the fire-ring area (if indented) prior to machining to work-harden that critical area. In the trade magazine Professional Motor Mechanic (PMM) (Feb 2010), Ultra Parts, the manufacturers of composite and MLS gaskets, state "surfaces finishes should be commercialy smooth. A mirror finish is ideal" as well as "assembly conditions must be clinical". I don't wish to rekindle the skim vs no-skim argument, but the article states "heads should be refaced as a matter of procedure. Both the block and head faces must be flat and parallel within 0.003" of flatness." They also say not to panic if minor leaks are noticed between the head and the block because the viton or silicone sealing surface has to soften under initial run-up temperatures and, if neceassary, one should repeat the run-up procedure when cold to aid the self-healing process.
As mentioned in this topic, they state the liners must stand proud of the block. The PMM article states 0.002". I've more commonly seen figures closer to 0.005", but the one thing all are agreed on is that the liner heights above the block must be the same.
Head bolts should be lightly lubricated with engine oil especially under the bolt head and the head of any washers fitted. And Ultra Parts is adamant that no sealants of any kind should be used on the head gasket. (In my ignorance 5 years ago, I used Hylomar on the MLS gasket and shim without detriment, but I won't be repeating that error this time.)
