rocker shafts / cam towers

[tmctguer]

i am pretty convinced that a small oil leak i have is due to leaking rocker shafts. i have read some prior posts on the topic.

using the Pelican Parts scale of 1 - 10, how hard of a job IS it to check torque and clearances, and install the shaft seals with the motor in?

any special tools? i've heard of a 1/4 drive torque wrench from Snap-On, for starters. this will probably set me back a few hundred !

any thoughts, ideas, etc. would be appreciated.

[john walker's workshop]

it would be a pain to do them all in the car. locate the one that's leaking and just do that one. a small inspection mirror and a flashlight should find the leak.

[GIBSON]

John, in your experience, is it usually just one leaking? There's a lot of oil under those valve covers, is it fairly easy to spot the leaking one?

Bruce Herrmann

[9eleven]

and, once you find it, how do you replace the seal?

[GIBSON]

Since there is no seal as installed by the factory, you remove the shaft by first removing the pinch bolts, drift out the shaft, insert the new seals into the existing grooves and reinstall. Access is not as easy on some as it is on others, if I knew I had to do several I'd pull the engine.
My question is just how to be sure of which one (ones) leak.

Bruce Herrmann

[BK911]

When you take off the valve cover, there are parts of the cam housing where there's oil (where the rocker arms are), and parts where there shouldn't be oil (where you tighten the cinch bolts for the rocker arms). Drain the oil, pull off the valve covers, and as Mr. Walker suggested, use a mirror and flashlight to inspect the cam housing. If you see any oil on the cam housing outside of where the rocker arms are, there's your problem. It will probably be dripping down the housing where the cinch bolts get tightened. You probably won't be replacing seals, they are after market and you may or may not have them. If this sounds confusing, pull off your intake valve cover and look around. It should make sense after you look at it.

Good luck!!
BK

[964Cab]

What harm is done if they remain leaking ? I just did my '90 C4 valve cover gaskets and didn't know that there were places under the valve cover were their should NOT be oil.

[GIBSON]

As far as harm done, it's mostly the frustration of the leak. It seems to find it's way to the heat exchangers, some smoke is then present and pretty soon you can smell a little smoke inside the car. That's my situation, I'd just like to clean up the bottom of the engine and reduce the oil smoke smell.

Bruce Herrmann

[964Cab]

I'm confused as doesn't the valve cover gasket keep the oil from leaking out of the cam towers ? Or do you mean that the rear cam bearing seal is leaking ?

[This message has been edited by 964Cab (edited 08-07-2001).]

[BK911]

Yes, there are places under the valve covers that shouldn't have any oil. I'm not familiar with the 964's so I might be wrong about them, but definitely on the early cars. If you pull your intake valve cover, there are five sections in the cam housing. Three sections go around each of the intake rocker arms, and the other two sections are between the rocker arm sections. Really hard to describe. If you have a haynes manual, page 42 figure 43.2 shows it. You can look through these two sections and see your heads. This is where the oil drips down, eventually to your heat exchangers.

[964Cab]

I see what your referring to in the Haynes manual. I've changed the valve cover gaskets on both my 993 and 964 and they don't look at all like the rocker assembly in the Haynes picture (thankfully). The only way oil can fall and hit the heat exchanger in the 964/993 as best I can tell is if the oil drips out of either the oil return 4x tubes, valve cover gaskets, oil breather tube, or that rear cam oil seal, weaping early non-gasket valve/head gasket, and maybe via a leaking chain cover gasket as well ?

Is there a seal in the older pre-964 heads that is leaking ? If so what part name is that given ?

Many thanks

[This message has been edited by 964Cab (edited 08-07-2001).]

[964Cab]

Actually I was wrong as the heads looks like older heads even in the 964s, it's the 993 heads that are little different. A better pic is shown in the latest 9/2001 Excellence on pg# 157.

I assume the oil leaks past the rocker "O" rings down onto the heat exchanger ? Are those rocker shafts press fit into the heads or do they travel with "O" rings ? I see the oil return tube bores and the camshaft bores but what bore is that just below the rocker bore(s) (Excellence pg# 157) ?


[This message has been edited by 964Cab (edited 08-07-2001).]

[Jim T]

Does anyone have the part number for the seals?

[GIBSON]

The seals have a Porsche part number but my
local dealer buys them from other sources, says he can't get them from Porsche. Buy them from Pelican.
The rocker arm shaft is a slip fit into the bore and is then held in place as the pinch bolts are tightened up and the ends of the
shafts expand into the bore. It is important that they are centered in the bore as illustrated in the manual and that they receive the correct torque. Porsche never supplied any street car with the o-rings. All shafts do have the provision to accept the o-rings as Porsche must have thought them
necessary for some of the race engines.

Bruce Herrmann