MG ZR: Cams & Maps

[Ruan]

How on earth do you know it hasn't overheated... Just because the temperature gauge says it hasn't gotten hot, does NOT mean you've had air locks inside the head - if the head gasket has gone, you can bet your bottom dollar that combustion gasses have made their way into the cooling system, soon as that happens you've got potential for hot spots - soon as you get localised overheating, that's the worst kind of overheating, you've got areas that are cool, areas that are hot, bam recipe for warping. Not to mention once you've induced stresses into the head from heat in places spots, re-torquing it and then heat cycles will often cause it to settle not true.

The whole thing that you HAVE to take off enough to cause an increase in compression - not the case at all, soon as you touch the wheel to the surface, it'll instantly show up if the head is true or not, past that there is no need, if done correctly, you should be taking off absolutely fractions of mms to just get the head back to a perfect face. Something that you simply cannot do with some emery cloth, aloxide paper and wire wool.

Meh, do whatever you want, I'm just going off my experiences and research into it, you've got an engine that is prone to head gasket failures and you're not doing everything in your power to stop it happening again - mental IMHO.. Maybe if people gave a slightly more scientific response of "Get a DTI gauge on the head and measure at multiple points" - that might be better, but jamming a straight edge on and looking by eye IMHO isn't a good enough test.

For the record I'm not just saying "£50 is pocket change to me" - it's never was and still isn't! I'm just averse to people dishing out the advice of "don't bother if you've put a ruler on it and it looks OK"...