Airbox & proper tuning
 

Just a Red Line endurance test. Today we're tearing down an 83 911SC engine for a refresh. This car has 206,000 miles on it, and has been PROPERLY serviced since day one. Guess what, ORIGINAL AIRBOX! That's right, blue inspection decal, dated 1983, etc. So remember, proper tuning, valve adjustments every 15,000, NO pop-off valve.
Just thought you guys should know!

+1

Same camp here as well; seems like the pop off valves can cause as many problems as they solve and a big backfire will blow the box anyways.

Keep it tuned!

I hate to be that guy but I bet it leaks - the glue goes bad around the seam seals just from age. Dunk it in a bucket of water and see. I'm not a pop off guy either.

Yep we’ve seen a few high milers as well with no pop off. Can’t throw a band aid on a major tuning problem....

And let me guess, standard paper air filter too?

Yes Peter. Quite a few of them by now! Mahle air filters, Mahle fuel filters, and Mahle oil filters. Our filter of choice.

I had a frustrating no start issue after I adjusted the valves and it turned out to be the entire pop off valve had blown out of its mount. I vaguely recalled a very minor backfire when I first cranked it after the valve adjustment and oil change. I epoxied it back in and it started right up. It runs great 5 years later.