Necessity of Head Planning in Head Gasket Replacement: Dealing with Bent Ends and Valve Holes

Hello.
I have a question about the necessity of planning the head when replacing the head gasket.
I have read and heard several opinions on the subject,some say that it is necessary, others that no.
I do not know how physically looks like the process of planning the head.

The head is bent at the ends in tkz.
I do not know how the physical process of planning the head
I do not know how the head is bent at the ends in the so-called banana
Sanding to a straight plane after all, we grind mainly the center of the head, which after grinding gives us uneven height of the holes for the valves.(those in the middle will be shorter)
I understand that the differences are measured in millimeters, but still it is some kind of change in dimensioning.
Please provide specific information whether the head MUST be planned when replacing the gasket?


Greetings and thank you.

The head is planned only in two cases:

1. "Extreme" planning. , involving the removal of up to several mm of material in order to lower the head and reduce the volume of the combustion chamber - used in engines used in motorsports, aimed at changing the characteristics of the engine and increasing power,

2.Corrective planning - usually less than 1 mm of head material is removed, performed after determining the non-flatness of the adjacent plane above the value set by the manufacturer of a specific engine. There are engines, such as VW turbodiesels, where the manufacturer prohibits the planning of this element, the head in the case of dislocation is replaced with a new one.

Planing is carried out by grinding on a special semi-automatic plane grinder, of course, as the author mentioned the excess material is removed, which causes, for example, a change in the volume of the combustion chambers, but so insignificant that it does not affect the performance of the engine. An exception may be diesels, due to the very small distance between the valve plug and the bottom of the piston - when overhauling some engines, valve seats are then deepened.

robokop wrote:

Exceptions may be diesels, due to the very small distance between the valve plug and the bottom of the piston - when overhauling some engines, then a deepening of the valve seats is performed.

Or a thicker head gasket is selected. .

marek1977 wrote:

robokop wrote:

Exception may be diesels, due to b.

Or a thicker head gasket is selected.

As a substitute - however, the classification of gasket thickness is subject to another criterion - here it is the height of the piston protrusion above the engine hull that matters.

But we do not plan the hull, but the head. making the height lower and manufacturers anticipate thicker gaskets. This is the first time I hear to deepen the seats .

Thus, I write again - the thickness of the gasket is selected according to the protrusion of the piston above the engine hull, not the splaning of the head. How do you supposedly determine how many times the head has already been planned?



For example, VW RA, SB, 1Y, AAZ engines ....

If you plan the head, then you have a flush lower plane, and the alignment of the holes for the camshaft changes.In the case of long 6-cylinder heads, the lack of alignment often leads to the breakage of the camshaft even during the installation of the head.

Thanks for the answers.
It can be unequivocally assumed,that it is better to put a new head than to plan?
Currently head planning comes out quite expensive.
550 zł on CNC machine. (skoda octavia 1.9TDi)

Good. Plan your head by a millimeter and don't give a thicker gasket. Good luck.

marek1977 wrote:

Good. Plan your head by a millimeter and don't give a thicker gasket. Good luck.

And with that, my colleague has irritated me - please justify with relevant examples the necessity of a thicker gasket after the head has been flown. If it turns out that I can prove that the colleague is wrong, I will stick a warning for writing off topic.

robokop wrote:

marek1977 wrote:

Good. Plan your head by a millimeter and don't give a thicker gasket. Good luck.

And with that, my colleague irritated me - please justify with relevant examples the necessity of using a thicker gasket after the head has been flown. If it turns out that I can prove that the colleague is wrong, I will stick a warning for writing off-topic.

You know where I have your warnings? Functions have come to you and you want to show off? Well then read and learn.
You have nice data but you can't use it.
You have given the thickness of the gasket to the piston protrusion. But you don't know what to do with it. when you plane the head you add what you took off to the gasket thickness and see if you fit within the tolerance or if you should give a thicker gasket. And you can only use this data for yourself with a brand new head, but I don't think you are assuming such.


now give yourself a warning for writing off topic.

Sodekso wrote:

Hello.
I have a question about the necessity of head planning when replacing the head gasket.
I have read and heard several opinions on this subject,some say that the necessity of others that do not.
I do not know how physically looks like the head planning process.

The head is bent at the ends in the tkz.banana
Sanding to a straight plane, after all, we grind mainly the center of the head, which after grinding gives us uneven height of the valve holes.(those in the middle will be shorter)
I understand that these differences are measured in millimeters,but nevertheless it is some kind of dimensional change.
Please provide specific information whether the head MUST be planned when replacing the gasket?


Greetings and thank you

A head bent into a " banana" is only suitable for remelting.
A good professional measures the head before grinding, and assesses whether it is worth grinding.
The machinist will "dart" to align even a few millimeters - I know such cases.

And I think that the colleague has listened, read, and now is making excuses - where do they teach such repair technology ? And what has head planning to do with the thickness of the gasket ? I wrote - the thickness of the gasket is selected after measuring the piston protrusion above the engine hull, to maintain the minimum distance between the bottom of the piston and the head, set by the manufacturer. The valves are deeper anyway, below the plane. I will try to get an overview photo in a week. In addition, the spread of the thickness of the gaskets has just under 0.5mm between the largest and smallest dimension, so how does it relate to this planning by 1mm ? Because thicker oversize gaskets do not exist.
PS. Motronic, in VW diesels cracks between the seats are standard, even vortex chambers can crack.

Robokop wrote that "the thickness of the gasket is selected after measuring the piston overhang above the engine fuselage to maintain the minimum distance between the bottom of the piston and the head as determined by the manufacturer", hence my question, does this distance change after planning the head?

And if the protrusion of the piston above the fuselage is too big this means that something is wrong with the crank system and this is not eliminated by the thickness of the gasket.

This is now I will give an example on the data you gave and think about it. The first gasket 0.66- 0.86 piston protrudes 0.76 you took off the head 0.09 you give a gasket with one notch, you took off 0.2 your head lowered the chamber decreased the norm changed, you add to 0.76+0.2 gives 0.96. According to your data should be a gasket with three teeth. This data is to select the gasket.

Where did I learn? At the ford training center.

Motronic wrote:

The distance does not change, but the volume of the combustion chamber decreases.

Since the combustion chamber decreases, the distance also decreases.

Exactly as Motronic says. I will say this, if I "took" something away from the head I "give" it back to the head by the thickness of the gasket.

Marek1977, you have a twisted reasoning and I completely do not understand further what you want to demonstrate.Pistons are made by the manufacturer in specific selection groups, the same with the engine hulls and cylinders - it may happen that in identical engines, the pistons will protrude above the plane of the block by a different value - this is what different thicknesses of gaskets serve. This applies in diesels, where the clearance between the bottom of the piston and the head is minimal. The volume of this free space is of little physical significance to the combustion process - the actual combustion chambers are made either as head swirl chambers or as chambers in the pistons - their volume does not change with machining.

Motronic wrote:

The volume does not change, but the volume of the combustion chamber decreases.

Yes, especially in gasoline engines, however, I have not noticed the existence of oversize gaskets to compensate for this difference.

Robokop - you are a tinkerer spoil!!!! You break people's cars and take money for it!!! You're a paperboy!!!

Moderated By robokop:

Recent arguments have run out mate ? For slander thrown publicly against my address I block access to the forum , until the situation is handled by the administrators - unless the colleague can prove that I broke someone's car and took money for it.

Well - it was going to be an interesting substantive discussion - as you can see some people let go of their nerves and resorted to rather strange arguments. I close the thread as exhausted - before the situation repeats itself.

For the sake of completeness, what Opel on this : .

Let's start with the fact that a head bent into a "banana" is to be discarded and rarely occurs in practice. A few years back I repaired heads and pay attention to what you can see when you inspect the head on the scribe board: the area around the holes attaching it to the engine fuselage is bulging. As a rule, we planned the head by milling only "to whitewash", after which very precise measurements were taken to see if the height was within the acceptable standard. If the head was so overdrawn that planning had to take more material, a gasket of increased thickness was used. I am in favor of milling, for the reason that it leaves a small scratch on the surface, which has a beneficial effect on the stability of the gasket.
Gentlemen, each of us has his own "patents", developed in practice. I have never had a situation where a customer had any problems with a head I repaired and installed, most of the cars I repaired several years ago are still running without problems today. Let's not rely only on professional literature and training, because our private patents are sometimes much better than those taught to us by professors-theoreticians, who have only seen the engine in parts in the workshops of their universities.
marek1977, you surprised not only me.... Did you let your nerves go? It promised to be a really interesting discussion, between people who have been involved in mechanics for years, and you pull such a stunt, like a child of the neostrada. Someone else your account is not using by any chance? You should now extend your paw and apologize to the person concerned for these moments of weakness.