Topic

After a head gasket failure is it standard practice to get the head skimmed and pressure tested?

Many thanks.

Tested yes skimmed not if it can be avoided ie if it does not need it then best not to skim it

It's common practice amongst bigger outfits, but not necessarily essential.

Practically, your head should only need skimmed if there's no longer an entirely flat surface to it, and many would say this can only be done once in it's lifetime otherwise there's a serious risk of removing the hardened surface entirely.

Economicaly, the bigger outfits will place as much weight on their warrenty and liability as their mechanics judgement and experience .... and since the customer will often be the one paying, they tend to 'play safe' and opt to skim. This removes the risk of a further HGF failure that they would be liable for in the event of a mechanical misjudgement on the part of their spanner monkeys.

Yep, only skim if absolutely necessary: alloy heads are often skin hardened but this is only a few microns deep (kin thin)
Flatness can be tested a number of ways: a straightedge placed in various planes and a bright light will show any distortion as gaps between edge and head. Best way is to check it on a faceplate with engineers blue, but this is probably a dying art now.
Excessive skimming will raise the compression ratio unduly and may require a packing shim to restore back to standard.

when i worked at rover they didnt like skimming the heads,we used to get memos all the time from the factory regarding this.check the surface,we where told to skim to level the surface and not the skim to remove damage.but that was 15 years ago when the hg issue was full on.as john said they are hardened,all to often garages will skim the hell out of them to remove damage.

Only a very small amount can be skimmed from a K series head, the max is about 8 thou and Roger Parker MGOC reccomends that a blunt cutter is used to produce a rougher surface and use a head saver shim. Russell told me that he had recently refixed a head gasket that had been done as short while before and the numpty had not fitted the shim , didnt think it was needed and threw it away.