Venting clearance..., Help please Options

[TheCabinetmaker]

engineers don't just pick a number out of the air. They do things for a reason. Would you guess, and adjust your valves at .002 instead of .008 just because you have trouble getting the feeler gauge in place?

[DaveO90s4]

Hi Zach - yes I agree. 0.004" is indeed minute. In practice it is "lightly touching less that minute amount" - hence my question. Thanks for your reply - I did use feeler gauges to set the venting clearance - was just wondering if feeler gauges were essential.

And in reply to The Cabinetmaker in a similar vein. I'm not bloody stupid you know. I own and maintain six aged Porsches, do all my own mechanical maintenance. Adjusting venting clearance with feeler gauges is not at all the same as adjusting tappets with feeler gauges. With tappets too much gap makes for a rattly engine and poor performance. Too little makes for burnt out valves. And allowance needs to be made for expansion as the engine components - alloy and steel alike - heat up.

With the brake venting Porsche clearly, at 0.004", wanted it to be as close as practicable without actually touching. As Zach helpfully notes, less than the thickness of a human hair.

As I say above, I have done the job properly as per spec. I was just interested to know if using feeler gauges was absolutely necessary for a competent experienced person who has done this task previously with the use of feeler gauges.