Leaking rocker shaft x2

[pub911]

I'm at a loss. My '78 911SC has been smoking like a chimney for about 3 months. For the record, the car's got a 1/2 million Klm's on it and was rebuilt about 250,000 Klm ago. But she runs incredibly strong and I have no other engine issues.

I've traced and fixed all the easy stuff on top (all 3 of the devil's triangle: oil thermostat, breather gasket, sender unit), then I got into the tougher jobs: removed and pressure tested engine oil cooler, replaced its 3 seals, valve cover gaskets and any hose that looked like it had any chance of contributing to the mess.

Then I went deeper into my engine than this garage hack has ever been. I was able to see evidence of wet oil on the external side of the rocker shafts of the #1 and #6 cylinders. I read up on all the forum posts on torque and RSR seals and followed the advice - seals in, re-torqued, even a new shaft on the worst of the two along with new hardware.

After 8 hours of laying on a cold garage floor, she's back together and running as strong as ever, BUT THE LEAKS ARE STILL THERE! I'm really at wit's end.

I'm not even sure if a tear-down and rebuild would fix this based on what I'm seeing. Do I need to throw away my cam towers? Is there anything else I (an admitted hack) can do with the engine in the car, or out if I have to?

I'm to the point of crazy thoughts now...can I fabricate some sort of sheet metal to funnel the leak away from the hot exhaust and just let it drip until I commission a rebuild in a few seasons?

Thanks for any help you may have for me.

[kodioneill]

I feel your pain but all the work was not in vein. It very well could be your upper valve covers I've seen this many times they may be warped causing the oil to leak inside and down.

[Bob Kontak]

pub911 - Welcome. Thanks for a well articulated post.

[pub911]

Thank you for your replies. I double checked the upper covers - wish it were as easy as that - but nope, they're dry, and I'm about 99% sure on the diagnosis of where the leaks are originating. It's from around the circular cone-nuts that hold the 2 leaking rocker shafts in place.

I know I'm grasping at straws, but could the pressure inside the engine, once up to operating temperature, have changed causing oil to blow out of all of these places at once? FYI, oil pressure gauge reads where it usually does...ramps up to between 2 and 3 upon normal acceleration (4K to 5K rpms) and then settles to between 1 and 2 at cruising Rev's of around 3K. I'm sorry, I don't know if the 1-5 gauge is an abstraction or reading an actual unit of pressure.

I'm just wondering (hoping) if perhaps there's some coincidental cause. Along with the onset of the smoke, it seems I started to notice, then fixed, oil weeping from a BUNCH of places: oil-pressure sending unit (the one next to the fan), oil lines to the upgraded carerra tensioners, hard oil line threaded fitting that enters the left side of the case. I'm also noticing very very small air bubbles - I know this sounds weird - getting past the trailing edge of the left-side lower valve covers after a hard drive.

Or is all this the earmark of an engine in need of a complete rebuild? Yikes.

[VFR750]

Well one easy answer: pressure gage units are called "bar" or "atmosphere" both are used, and are equal to 14.696 psi. It is understood that 0 bar in your gage is really the pressure of the air surrounding you "atmosphere". 1 bar on your gage is 14.7 psid, over the atmospheric pressure.


Cold oil will have very high pressure: 5 bar is over 73.5 psid at low rpm. So any small leak can flow a lot of oil with that kind of pressure pushing it.

[VFR750]

Psi = pounds per square inch
Psia = psi absolute (0 psia = equals a hard vacuum, like space, or a really good vaacuum pump)
Psid = psi delta. Often used interchangeably with the simpler psi or psig. Just means the pressure was measured to a reference pressure. In our case the reference pressure is "atmospheric" and for those of us near Sea Level that is 14.7 psia.

You may already know this. I though i'd go into more detail for those that might want the details. Hard to tell what others know/dont know while sitting here typing....

[kodioneill]

If you have foaming, smoke and lots of leaks it sounds like an overfill condition.

[timmy2]

Recently saw a post about a company in England that makes sealing rocker shaft cone nuts.
Not the rsr seals. On Youtube as well.

[NOLAsc]

Originally Posted by pub911

My '78 911SC has been smoking like a chimney for about 3 months.

The smoke is from oil dripping onto the exhaust, not smoke coming out of the exhaust, right?

[Ken911]

You might want to make sure the rocker arm shafts havent walked. If so then the bores of the cam housing might have opened up. This happens over time with rocker arm shafts being changed tightened over tightened etc. Turbo kraft has rocker arm shaft locks that prevent this from happening. It replaces the cones which you said are leaking. If the hsafts are leaking around the cones then possibly the shafts might have cracked which is common also if the bores on the housing are oversized.

[Tippy]

Did you torque them above the factory torque rating? If not, that might be the reason.

They require higher torque after rebuild due to wear over time requiring more pinch to seal.

[pub911]

Originally Posted by timmy2

Recently saw a post about a company in England that makes sealing rocker shaft cone nuts.
Not the rsr seals. On Youtube as well.

Anyone have a link? Or can Pelican get this after market part?

Thank you for the oil gauge education - much appreciated. I'm assuming 2 bar at cruising revs is ok?

And just to answer a few other well intended questions raised below. The smoke is from oil dripping on the exhaust from the leading lower corner of the right side valve cover and the same corner of the heat-sinc'd cam tower. This is not an oil overfill condition. The smoke occurs at rest when the car's up to operating temp.

thanks, much!

[timmy2]

Here's the video:

N Fulljames cam timing.wmv - YouTube

Redtek in the UK according to this post:
Rocker Shaft bolts

[pub911]

Thank's Timmy2.

Has anyone tried these:
TurboKraft : Catalog Home : Rocker Shaft Lock Set [901 105 360 TK] - $359.00

[timmy2]

Guess you would have to e-mail him for more information.
Watch the video around 5 minutes or so in.
RedTEK

[pub911]

Originally Posted by timmy2

Here's the video:

N Fulljames cam timing.wmv - YouTube

Redtek in the UK according to this post:
Rocker Shaft bolts

I just watched the video - did he put a seal on the cone bushing? Is that seal different from the RSR seals that are slipped into the slits on the rocker shaft?

I can't find RedTek mentioned or a listing of them online anywhere. Does anyone have a link?

[pub911]

Thanks for the link!

[timmy2]

From what I understand the cones are machined with a lip to accept an o-ring and that is how it works.
The TurboKraft setup looks pretty good too.

[pub911]

So I talked to Nick from RedTEK and what he says is that he has the hardware custom made and notched to accept a seal on the cones. He's digging around for me to find me a couple rather than having me spring for a full set of 6 (at 170 British pounds).

But here's an interesting idea from a guy at Turbocraft (link above). He sells 'locks' to prevent the rocker shafts from walking. And while he acknowledged that his locks will not likely address the leak, he did offer something else he's tried with success.

He suggests thoroughly cleaning the offending end and loading it up with high-temp silicon (RTV Red or similar). Now that sounds like a hack-job to me, but geeze, I've been at this for months and I'm nowhere. I think I'll give this a try. Anyone have any engineering objection to the idea - spiritual objections are a given

[kodioneill]

FWIW I would never use silicone anywhere on an engine. I've never had a shaft walk out or leak of all the engines that I rebuilt or resealed. I torque the shafts to 21' lbs. Make sure the cam tower is not scored.