Why does the piston to head clearance decrease with heat?

[winders]

Originally Posted by Ollies930

What I am saying is that even Porsche engineers can make mistakes and if someone up high in the main office tells them to make it work because they have already spent a fortune on material research, then they will try to make it work.
But rather than deflect, explain to me why no one else needed Dilavar, when the engineering and mechanical guidelines remained the same. And if Porsche engineers always got it right, then why so many different Dilavar stud designs.
And how come the IMS shafts were failing in 996s and 997s when these were designed with finite element analysis computers. No one is infallible.

Who else had air-cooled engines with same design and characteristics as Porsche engines? No one....

Also, Porsche to this day recommends dilavar head studs for air-cooled engine rebuilds. All the head studs have been superseded by the 993 Twin Turbo part number. I guess they just continue to be stupid....

[Ollies930]

So you are saying that a head stud can tell the difference if it is mounted in a flat six or V8 or I4? Wow, those really are amazing head studs.
As far as Porsche still selling them, so what? They also kept selling 996s and 997s, knowing full well that a very large numbers of IMSs were going to fail.
Rather than saying "because Porsche", give me a logic or engineering based argument why failing Dilavar studs should be used rather than steel. The difference in expansion rate between steel and dilavar is in the range of approximately .002". If you use studs with 1.5mm thread pitch, then that would be the equivalent of an additional 12* of torque. 12* would probably add another 2-3 ftlbs of torque. You will easily get that much difference using different assembly lubes on the threads. That will not cause significant enough pressure on the cylinders to cause warping.
Your argument please!

[reclino]

Let's prevent this becoming another Dilavar thread. No one wants this argument anymore. No one here is bringing any data to the table. Go build your engine the way you want, spending your money on the parts you want. If someone asks what parts you suggest, then give them your answer.
Simple.