Has anyone Surface Machined a 300TDi head?

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Originally Posted by Waxenwane

I would have thought the increased cylinder pressures will enhance performance. As I said I heard about this from someone who saw it.

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That was my point - there will be no increase in cylinder pressure. In a domed head engine - sure, but in a flat head engine, compression ratio remains unchanged.

The combustion chamber is in the piston, so you would have to reduce it's volume to increase compression ratio (I assume that is what you are talking about) or increase the bore diameter to increase the swept volume.
Thanks all for the info and advice, the head is being machined and the valves adjusted (machined) to be the correct height above the pistons for proper clearance, Regards Frank.

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Originally Posted by Tank

The combustion chamber is in the piston, so you would have to reduce it's volume to increase compression ratio (I assume that is what you are talking about) or increase the bore diameter to increase the swept volume.
Thanks all for the info and advice, the head is being machined and the valves adjusted (machined) to be the correct height above the pistons for proper clearance, Regards Frank.

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I'm told by the experts that what is being done (setting the valves back to clear the piston) is correct and that as it is a "flat head" that there is no concern re about the theoretical increase in ratio that you mention

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Originally Posted by isuzurover

That was my point - there will be no increase in cylinder pressure. In a domed head engine - sure, but in a flat head engine, compression ratio remains unchanged.

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Makes sense, but if the valves are not recessed as well surely there is some increase?

I'd be more concerned about the pistons deadheading on the head,you could do it but a thicker gasket would be needed.Back in the day I used to take 1/8'' off 2.25 heads to get them to go but they were low comp engines so they needed it. Pat

Where did my other post go???????
Pat, the head face is flat. No matter how much you take off, the piston will never come into contact with the head face.
The valves however are a different story. By reducing the headface thickness, the valves will come closer to the crown so basically you need to recut the valve seats by the same amount to maintain valve to crown clearance.
Using a thicker head gasket is only to increase clearance for piston protrusion, not headfacing. This will have an adverse effect on CR.
The only time piston protrusion will change is from new pistons and/or decking the block.
As there is no volume in the head and with the small channel between the valves, you will not get any CR change by skimming as the piston carries the chamber volume.

Cheers

andrew.

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Originally Posted by LOVEMYRANGIE

Where did my other post go???????
Pat, the head face is flat. No matter how much you take off, the piston will never come into contact with the head face.
The valves however are a different story. By reducing the headface thickness, the valves will come closer to the crown so basically you need to recut the valve seats by the same amount to maintain valve to crown clearance.
Using a thicker head gasket is only to increase clearance for piston protrusion, not headfacing. This will have an adverse effect on CR.
The only time piston protrusion will change is from new pistons and/or decking the block.
As there is no volume in the head and with the small channel between the valves, you will not get any CR change by skimming as the piston carries the chamber volume.

Cheers

andrew.

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Andrew you are spot here.
Being a retired spanner you have saved me a lot of typing.

Dave.