The BMW N42 fails to start subsequent to the replacement of the valve seals.

[BMW_Fan2020]

I replaced the seals without detaching the cylinder head, using the rope technique and a universal lever tool. The vehicle fails to start; it attempts to engage but does not succeed. A spark is there, accompanied by the odor of gasoline, and the timing is appropriate as all tools are compatible. The cylinders exhibit no compression, with values ranging from 1.9 to 3.8 bar. I have calibrated the Valvetronic system using ISTA, and there are no diagnostic problems present. The vehicle has traveled 164,000 kilometers.
I have inspected the pistons beside the chamber, and there are no markings; they are coated with carbon, indicating that the valves have not seized.

[BMW_Fan2020]

Do you believe it is feasible to distort the cylinder head using the valve spring compressor tool?

[BMW_Fan2020]

Negative. This tool will not distort a cylinder head.

Have you verified your valve clearance?

[BMW_Fan2020]

Executing this procedure without elevating the cylinder head by threading a string through the spark plug aperture obscures the view of the valve seat. It is peculiar that several others have used this method without encountering issues, nevertheless all of my valves are inadequately seated.

[William_Brown2000]

Do not assume that this action will distort the skull.
The camera's orientation is correct; but, I am uncertain about this engine. Last year, I saw a vehicle with the intake and exhaust incorrectly positioned.

[BMW_Fan2020]

Indeed, with the curved section oriented upwards—there was an instance when it was positioned downwards—the timing is optimal, and the tools fit seamlessly without exertion, resulting in a tiny deflection of the exhaust shaft.
It is evident that either the cylinder head is warped, which appears implausible given that the cylinder's explosive forces can attain 80 bar—tenfold the unlikely 200 kg per screw that the tool can exert—or that the valvetronic system is preventing the valves from fully closing during compression.

[Martin_Smith76]

I cannot provide more commentary, my friend; I have reviewed the strategy you used, and it is not one I would personally endorse. It is hoped that someone somebody with a similar experience may provide assistance.

[William_Brown2000]

It is difficult to see how they might be inadequately positioned, considering they are referenced in a guide and secured by the rope.
As previously said, verify the valve clearance.

[William_Brown2000]

It is difficult to see how they might be inadequately positioned, considering they are referenced in a guide and secured by the rope.
As previously said, verify the valve clearance.

[BMW_Fan2020]

Upon examining the matter, I believe the most probable culprit at startup may be the valve lifts. I removed them during the task, and they remained in a horizontal position for a day and a half with the drain hole facing upwards. Some may have leaked, resulting in a loss of fluid, allowing air to enter, which might cause them to become rigid and perhaps keep the valves open, so leading to a reduction in compression. Upon beginning, there seems to be inadequate oil pressure to facilitate their drainage.