Below is a picture of the bottom of cylinder 1, nice and clean, and cylinder 5 - with what appears to be 2 very slow, small leaks. These leaks concern me, since when I pulled the plugs all looked the same except #5 was wet with oil. No other cylinders have this kind of leak, and all the other plugs looked good.

Any ideas? I plan on checking the head bolts when I check the valve clearances in a month. This is a famous magnesium case (77 911S)... it had an upper-end rebuild 10,000 miles ago, unfortunantly the head bolts were cleaned but not replaced.

Thanks, Joe

 

Joe:

Looks like a base gasket leak to me.

These engine's studs are steel and VERY reliable. The worst thing you might have are pulled studs due to case thread failures and that allows the studs to relax their grip holding the heads & cylinders down.

When you do your next valve adjustment,...using an accurate torque wrench, VERY carefully check all the head nuts for torque. If you find some that will not pull up to spec, you've found a pulled stud(s) which requires disassembly and case repairs.

 

I'd bet on the base gasket.

Seen it before on my 82SC. Mine was broken studs.

It just plain sucks.

 

Does anyone know what the torque spec for these head bolts are? It is a '77 2.7 911S.

 

My book says 21 ft lbs.

Can someone confirm

 

23.5 lb/ft...There is a small range acceptable, but this is the number that I've always used (the max spec is 23.8). Do all the nuts at 18, then go to 21, then to 23.5.

 

Pete

For what its worth my info came from the manual that starts with "h" and ends with an "s".
BTW is there any difference between magnesium and aluminum.

Just curious

 

I also have that as my spooge point of origin. Perhaps next spring when I do the clutch, it'll be pull-it-all-apart time.

 

Mussberger: Cylinder head torque, through the last mag case, was stated as a range between 3.0 and 3.3 kpm (multiply by 7.23 for lb/ft). The first SCs (aluminum cases) were listed as 3.3 kpm, and then '82/83 cars had an additional instruction: 1st step = 1.0 kpm; 2nd step = 3.2 kpm. Then the whole deal really changed for the 3.2 liter cars: 1st step = 1.5 kpm; 2nd step = 1 x 90 degree turn (+/- 2 degrees) torque angle. 3.2 liter engines use a different cylinder head nut, and beginning with '82 cars an additional instruction calls for the lubrication of cylinder head mounting stud threads and head nut bearing surfaces with a light coat of Optimoly HT.