What causes leaky rocker shafts?

[sww914]

I've completed several different searches, but I haven't learned the causes of rocker shafts leaking. If I make sure that everything is polished smooth, perfectly clean and properly torqued, will they stop leaking? I was sure that I did that the last time, but they still leak.
Also, does anyone have a diagram showing which shaft end faces which direction for each shaft? Again, I think that I have them in right, but I'm copying the way that they were installed in the engine before I took it apart and I don't want to buy the $250.00 factory manual right now if I don't have to.
I know that RSR O rings are available, is that the only way to stop this mess? I dream that I can fix it without the O rings.
Sometimes dreams come true, but the percentage isn't favorable, is it?
Thanks for any help you can provide.

[cstreit]

I don't think shaft direction is critical to sealing. I always use the RSR o-rings on our engines, cheap insurance.

[WERK I]

It's really due to dissimilar metals (rocker arm versus cam tower ) with different expansion/contraction rates plus the ability of oil molecules to travel through the tiniest of orifices. The oil is weeping and although the RSR seals are a definite improvement, the best solution was when Porsche changed the whole damn design of the rocker arm mount in the 993 engine.

[911 tweaks]

Chris: what is the p/n for the rsr seals and what yr (S) to these seals work on for the 911 engines?

Thanks!

Bob

[Mo_Gearhead]

sww914,
From my reading I learned: Cleanliness first! Then install the shafts DRY, meaning; do not lube the rocker arm or the shaft until AFTER you have the shaft in place and torqued. (You can then apply oil into the rocker arm 'lube hole' and P-car engines build oil pressure rapidly.) This keeps the metal to metal surfaces dry and more likely to seal.

Orientation of the shaft end is only critical on the ends of the engine where the oil cooler, cam covers, etc. impeded the insertion of your allen wrench. On mine I have the larger allen size 'sawn off' to clear, so I put the larger 'nut end' out.

[ChrisBennet]

The "trick" I think, is not to score the bores when you remove them. I always take them out and put them in from the end that the rocker shaft is closest to. In other words, the rocker shaft will be peeking out of one side of the bore -- less chance for dirt or corrosion on that side of the bore.
I use the RSR seals. I can't seem to find the part #.
-Chris

[madsonryan]

Here is the Pelican part #99-0579-052-M260

[fastfredracing]

I agree with cris, most of the ones that I see leaking, are loose, improperly tightened/positioned, or the bores have some scrapes and or gouging. The rsr seals have worked real well for me , I even had a rocker shaft fall out, and the bore was all boogered up. No leaks after the seals were installed.

[afterburn 549]

put the seals in. end of problem

[sww914]

So, I've ordered the seals, and GPR tells me that they're the same as turbo rocker shaft seals. does this sound right?
Also, what should I lube the shafts with to ease installation? I have some cam assembly lube, small block chevy type stuff, it's red grease. Or, should I just put a drop of oil or maybe a drop of Tri Flow on them?

[ChrisBennet]

Put the rocker shafts in dry, dry, dry. Remember, all that is holding them in place is "The Miracle of Friction". Squirt some oil in the oiling hole after the rocker is installed.

"Oh but Chris, the seals rip if I don't oil them."
If that concerns you (and why shouldn't it?), do a test. Examine a seal, pull on it and look with a magnifying glass. Now install it dry and then pull it out and check for tears. I haven't tried this but I encourage you to try it if you have any worries. I am wrong about stuff all the time!
-Chris

[304065]

One cause is that somebody doesn't relieve the pressure for the cam before trying to remove the rocker, resulting in the shaft marring the bore as it is removed. Still worse is the hack that drives the rocker out when it's sticking with a hammer without removing the pinch bolt and expander and nut and lubricating with PB blaster and heating the aluminum bore to expand the clearance before driving it out.

The worst thing is you look in the bore and there's a deep groove from where the shaft was driven out. Junk.

[afterburn 549]

silicone grease ?? worked for me.

[911quest]

Most of the time if look at them real good you can see damage this is cracked from being overtightend this one is actually cracked top from bottom

[RoninLB]

i used dino oil with new shaft seals w/new cam install. It was impossible for me to install dry as with no shaft seals.. result is no leaks.

[hcoles]

as Chris and others mention.... carefull and proper removing without marking the bores is key.... then carefully clean bores.... I used the O rings and asm. lube and I have 1 or 2 that seep very very slowly... not perfect but I guess ok for my first time. If I was doing it again, I think I could do a much better job. There are also mention on other threads of over torquing to some extent to provide a better seal and not have the shafts come loose. IMHO - it is not a great design but good mechanics can make the design work ok. I ended up making some new rocker bushings for myself and honing to a final fit on a proper machine.. so far so good. I think a much better job could have been done... many of the good mechanics on this site are able to do all of this with 99% or better results.