I have a 300Tdi head which is seriously warped. Combine this with a cylinder block which has had new liners installed and the top skimmed.
Can any one advise how much you can really skim off the head? The manuals say you shouldn't do it. .................
I suspect that I will need the thickest gasket going and may be reseat the valves further into the block, or skim the piston heads. Maybe easier to buy a new block!
What my local engine bodge shop does is re-cut valve seats then skim the head with the valves fitted, this removes any valve head that may be protruding. Don't know what this will do for longevity of the valves, butit works for them.
Cheers, icky.
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Now that is a real bodgit. I always thought that steel and aluminium had different cutting tools and this really makes me cringe. I wonder if any body else has any thing better!
Griffith
Skimming with the valves in place is a widely accepted trade practice. Unless you're skimming outrageous amounts off the valves it causes no problems whatsoever (and is much preferable to valves and piston touching).
It's not a bodge at all if you're skimming the head properly with a surface grinder. The stones used for surfacing a head are generally a universal type suitable for both cast iron and aluminium heads. The biggest bodge is not hardness testing an aluminium head before surfacing it - if it's gone soft it'll only ever give problems as it'll just change shape when torqued down rather than providing a clamping force on the gasket.
On or around Sat, 16 Jun 2007 12:06:52 -0000, Griffith enlightened us thusly:
How did it get warped?
I've heard it said that if the head's been seriously overheated, then it's a waste of time skimming it.
I bought it off e-bay at a low price and being 1500 miles away it was not possible to check it before I bought it. The guy selling it said it was okay. "Just slap it on" he said it was the first item that I have bought on e-bay and I'm sure you have a good idea that I will now buy anything with caution. ( What is it they say "buyer - be aware!" - too flipping true, ouch!!")
The two centre valves are misaligned too the extent that there is about 0.5mm on one side of the valves, the others are fine and I suspect that it has been overheated. It is kind of taken up a copncave shape. I am tempted to clamp it down after I have ground the valves in but I am beginning to feel uncomfortable about it, so I may start looking for another head.
Griffith of Gibraltar.
On or around Mon, 18 Jun 2007 10:36:41 -0700, Griffith enlightened us thusly:
If it's had a cambelt go the valves might be bent, worth a check. Sorry to say that it sounds iffy. You can machine the head to flatten it but not much. take too much off it and even with a fat gasket the valves can hit the pistons.
The reason cited for not machining ones that have got seriously hot (and we're talking engine-seizing hot, here) is that the alloy is heat-treated and getting it too hot softens it. I'm not enough of a metallurgist to know if that's bullshit, although it was a reasonably reputable lot that told me.
Having had a closer look at it, it would appear that the head gasket had blown between pistons two and three, also there are small cracks coming away from all the pre-heaters. The valves are perfectly concentric when I am trying to grind them in. I am 80% on the way to throwing it in the bin but I will take it to a specialist tommorrow in Spain, trouble is my technical Spanish is not that good and they know it and take advantage, its a laugh really. I have already asked them for a price for a new head - 1200euros!
Tony
Island4x4 in the UK do brand new 300Tdi cylinder heads for =A3269.99 + =A320 delivery to Spain. Don't know how many Euros that is but I guess it's a lot less than 1200.
Turner Engineering also have some but complete with valves, springs etc.. Obviously a bit more pricey but a 'drop on' job.
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