[Brotok]

Originally Posted by Brotok View Post
I made a typo in the original post (now corrected): Porsche recommends re-adjusting the valve clearance after 30 minutes, not the timing - my apologies. This is in a short paragraph on page E79 of the workshop manual, and pretty much states what I have reproduced here.

Does it actually say in the workshop manual to adjust the valves at 0.25mm for a break-in?

In the valve job section of the workshop manual it says to adjust valve clearance to 0.15 mm in excess of standard adjustment for bedding in the valves, and to run the engine for a 30 minute test run before re-adjusting to standard clearance.

There is some logic behind ignoring Porsche's recommendation to re-adjust valves after 30 minutes of running the engine, and I doubt that this would be the first time that Porsche's recommendation is controversial. The logic follows:

Nothing wrong with checking the valve clearance per recommendation but I cannot buy into setting them two and a half times normal clearance

- It is dangerous to run valves that are too tight, e.g., tighter than 0.1mm
- It is not dangerous/harmful to run valves a bit too loose, e.g., slightly less than 0.25mm (actually, 0.25 is the clearance used on many BMWs for normal operation).

Appels and oranges. Different engine, cams, overlap. Valve-lash for exhaust valves is more critical than the intakes but 0.25mm is not just a bit loose, it's over the top. Did you time the cams with 0.25 or 0.1mm?

I agree that BMW and Porsche engines are very different but I still do not see the harm that could be caused by opening valves slightly later, and I don't imagine that 0.25 mm is so much space for rockers to bounce around as to cause damage. On what do you base your conclusion that 0.25 mm is over the top? I timed the cams at 0.1 mm of course.

Does anyone agree?

Anyone ever went with very loose valves for a break-in?

Thank you for bringing all of this up

Thanks to everyone for their input