Good compression, do you split the case?
 

I am tearing into a 2L 911 engine. Compression is 167 min to 175 maximum all across six cylinders. Have not done leak down test...

Would you split the case?

M

You might explain a bit more what you are up to.

Good compression (and good leakdowns) usually indicates that the top end is OK. In which case, why would one take it apart? Rendering moot the issue of splitting the case.

Splitting the case is for main bearings (rods, too, if you want to use bolt stretch), checking crank, checking for line bore, dealing with IS gears, oil pumps, and sundry other things. Of course, if you wonder about those things, you'd do a full teardown, as it is not easy to figure out externally if all this stuff is still just fine. With race motors, guys set a number of hours between teardowns. Shops with lots of racer customers often have good data on this. The rest of us mostly guess, or watch out oil temps carefully as hours accumulate. But with an engine of somewhat unknown history, there is a certain amount of pig in a poke at work.

This is a 914-6 engine with 180,000 miles. I am told a rebuilt was done at 90,000 miles, so it is 90,000 miles ago. The owner, my neighbor, says that his engine sounded tired, leaks a whole bunch of oil in all places, shifts funny, and just needed a lot of love. So, he asked me to drop the engine, inspect it, recommend what to be done, and stop the leaks. He will drive it only sparingly, but he definitely wants the leaks stopped.

We dropped the motor today after we did a compression test. The leak down will be done with the engine on the stand. So far ...

Compression is acceptable.
Leaks everywhere.
Bushing for shift rod is totally gone.
All hoses are hard as rocks
dizzy caps and rotors have not been changed in ... 30 years.
Wires are hard.
Spark plugs show running rich

I will have to remove the cam towers to reseal the engine. I think it can certainly use a valve job but with compression so decent, the bottom end may just stay that way. No reason to believe that oil pressure is bad.

Interesting task.

I take it you are pretty sure that the case seal isn't leaking? Everything else, pretty much, can be attended to. If you pull the heads and cylinders off (I gather you are pretty sure the head to cam carrier seal is bad, because otherwise you could take heads and carriers off as a unit), you could get at each through bolt one by one, if there is evidence that any of those are leaking. And the two stud throughbolts behind the oil cooler. New O rings and maybe some CurilT or other helpful adjunct? Chain housings could leak where they mate to the case, new gaskets etc. With cam carrier off, you can replace the carrier to chain housing seal O ring and gasket. Flywheel off to get at the crank seal there, pulley off at the other end. Not much you can do if the O ring around the #8 is leaking, though you can purchase some devices which are designed to help seal that joint externally.

I'd suggest not worrying much about the leakage from the rocker shafts. The external area outside each shaft end is usually pretty crudded up, but from slow seeping. You can try the rather expensive RSR seals on the shafts - some say they do real good, though they haven't kept my motors bone dry.

Or not - is this a pro bono effort?

There is no way to tell if the case is leaking along the seams. But, the leaks are so copious on the top of the engine and along the cam towers that if we stop those leaks, it would be 95% of the leaks.

I cannot tell if the nose bearing seal is leaking or not. In the past, I have been successful stopping the leaks from the outside. THe front and rear main seals will be changed. Intermediate shaft front seal will be changed. The cam towers seals will be changed.

Bottom line, unless there is a performance reason to split the case, I might leave that alone.