Head Gasket thickness

[Mr_Nuclear]

Hi all,

I'm in the process of replacing the HG on my 2.0 HDI as it was pressurising the coolant.

The head has been skimmed (6 thou removed).

Going by the Haynes you are meant to do piston protrusion measurements on all four pistons then cross reference the results to their table to work out the new HG thickness, this is a time consuming ball ache that I could do without. It had a three notch gasket on it and the engineers that did the head skim have said a four notch will be fine, thing is that I don't want to put it all back together to fine it's not.

Going by haynes a 3 notch HG is 1.34mm thick and 4 is 1.38mm so the difference is only 0.04mm and the same for a 5 notch (another 0.04mm). I'm struggling with the relationship between 6 thou (0.15mm) being skimmed off and the difference in gasket thicknesses being only 0.04mm increments.

Thanks.

[Piggy]

With 6 thou' taken off I would be inclined to go slightly thicker tbh.

[Mr_Nuclear]

With 6 thou' taken off I would be inclined to go slightly thicker tbh.

Thanks,

the thing is even if i go for a 5 notch its still only 0.08mm thicker than what it was?

[Piggy]

So 5 notch would be a better choice then than 4 notch

[Mr_Nuclear]

So 5 notch would be a better choice then than 4 notch

So the 5 notch is 1.42mm thick, the one that came off was 1.34mm thick which is a difference of 0.08mm.

6 thou is 0.15mm so even with the 5 notch the head is considerably closer to the piston isn't it? 

[Piggy]

It will have a TINY increase in compression, wouldnt think that would be noticable imho.

But once all the science boys have got over their hangovers I'm sure I will be corrected

[Mr_Nuclear]

It will have a TINY increase in compression, wouldnt think that would be noticable imho.

But once all the science boys have got over their hangovers I'm sure I will be corrected

Hi Piggy,

Im being really simple here!? what I'm worried about is the piston contacting the valves, it would seem there is next to no clearance as the piston actually protrudes out of the bore. The fact that the head has been skimmed puts the valves closer to the piston.

[bashbarnard]

Its such a minimal distance. Bang a five on there. Torque up. Time up. Turn over by hand. I xant see there being a problem. I think our over thinking this. We are talking less than a 10th of a mm diffrence in thickness. If your torque wrench was out a few nms id say a five could quickly be squashed to a four.

[Uberderv]

Here is the chart I have -