Quote:
Originally Posted by Steve@Rennsport
Walt @ CE, Jerry, and Bruce are all correct; Porsche installed a batch of defective outer valve springs in the 79-81 model years and this has been well known problem for many many years now.
I started seeing those in 1980,... 
I tell anyone with an SC of that vintage to press on each valve with your thumb at valve adjustment time. If you can push the assembly down manually, the outer spring is broken and requires replacement. This can be done with the engine in the car,.....
You'll hear a ticking (much like a loose valve) when a spring has failed and its VERY important to fix this right away. |
Bumping a very old thread here, but I wanted to update the records: I believe the bad run of valve springs also includes the '78 models, not only 79-81 as Steve previously mentioned.
I just replaced a broken #4 intake on a 47k original mile 78 SC, which is my second SC to have this problem - at the time of this thread I had just done one on my 81 SC, and the problem is almost exactly the same. That car had a broken intake as well, I believe it was also #4, though I think the cyl. number is just a coincidence. In both cases, the outer spring was broken but the inner spring was OK.
On the 78 I didn't notice a ticking as I had with the 81, but I noticed that I could push a rocker down by hand without trying particularly hard during my first valve adjustment on this car. The outer spring was broken into 4 pieces, and looked like it had been for a good long time.
Still curious why these break on the intake side, as John Walker mentions.
I'm really surprised these cars can be run to redline with a broken outer spring without valve to piston contact, but hey, I'm not complaining!