Head Skim? - MG-Rover.org Forums
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post #1 of 6 (permalink) Old 21-04-2007, 15:40 Thread Starter
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Car: Rover 25
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Head Skim?

I have taken the head off my R25. it has rings round where the valves are from the HG going.

What shall i do now?

I have been advised by a mate of mine that you shouldnt have rover heads skimmed as they will just keep failing. He told me to use sandpaper on the rings and get them smooth again.

Does it need a skim? Is this ok to do? Do i need to strip everything else off the head to get it skimmed?

Cheers guys!!
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post #2 of 6 (permalink) Old 21-04-2007, 15:52
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Hi! I'm not sure what you should do but when I asked the (ex) Rover dealer about skimming my head after a HGF they said that they'd never recommend skimming a head and that they'd replace it if it was warped
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post #3 of 6 (permalink) Old 21-04-2007, 16:01
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The rings you describe are reminance of the old head gasket. They can be removed by cleaning with solvent (brake cleaner works well) and lightly sanding the surface with fine sandpaper. Just be careful not to take actual metal off the head when your sanding it.

You dont need to strip the head down completely to get it skimmed. All the valve gear can be left in place but you have to take out the cams, and the hydraulic lifters. The lifters must be kept immersed in oil when they are out of the head or else they can lose the "charge" of oil within them.

The K-series head can only be skimmed a maximum of twice but most of the time these heads dont need it. Ive done a good few k series engines now and i havent had any of them skimmed. However, i do check them with my very expensive and accurate straight edge when they are off, this is to check if they are warped.

I say take the lifters out because when skimming, fine metal swarf can get in places you dont want it to. So take them out before hand then after the skim, clean the head down thoroughly and then refit the lifters to make sure no swarf has got in there.

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post #4 of 6 (permalink) Old 21-04-2007, 16:09 Thread Starter
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The rings are more of an imprint than HG left on there.
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post #5 of 6 (permalink) Old 22-04-2007, 00:33
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The head is soft if the rings are deep, deep rings = its scrap. The rings can be up to 0.75mm!!! Deep. If you can feel them with your thumb sanding them will do no good, refitting it like that is a sure fire failure, personally i'd NEVER sand any head by hand...

Refinishing machine is needed...

Skim is ok, just remember every 1/4mm 0.010" you remove is 0.27 increase in compression ratio making it more likely to fail again on 95RON fuel and increased cylinder pressure...you can skim up to 0.75mm off safely but youll need to run super unleaded and use a head shim 0.010" (0.25mm) land rover shim gasket...Aswell as the shim the gasket is 0.003" thicker so its a winner....You can mod the heads chambers to get back 2cc of the skim loss, this buys you around another 0.50mm of skimming...Head will be weak though, it maybe be ok...

So much lack of knowledge on this forum, no offense etc..Used to classis cars, you can tell modern owners just don't open the bonnet.
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post #6 of 6 (permalink) Old 22-04-2007, 00:38
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P.S saying you can only skim twice is pure fantasy...You can skim a head by 0.001"...You have 0.025" of safe skim potential on the average head using a shim gasket afterwards or super unleaded, thats 25 skims at 0.001" a time...I had my VVC refaced it was a 0.002" skim, thats like a hairswidth...
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