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I believe this to be true. I've seen too many dry 911 motors, including my own 22 year old factory built engine.

I find it amazing that with the age of the seals and gaskets more aren't leaking.

Also -- When I was 911 shopping, whenever I heard the defensive words of "they ALL leak" . . . I took that as the seller saying; "I want to pawn off a car full of neglected details."
YMMV

ITs what you have to do so it dosen't leak and sometimes the plain gasket, installed as it was ment to be needs some extra help. Mine does not leak now, but theres RTV on those gaskets, and the valve cover gaskets are the $50 aircraft ones, NOT the original by any means. By the way the only place I did not use RTV besides the valve covers was the o rings on the case bolts. No leaks there on any of the 3 times I rebuilt this thing.

PS I used Vitran o rings, the same size, but from a local supplier. Much better than whatever came in the original german Victor Reinz stuff.

Let's settle the air here, and agree on this statement?

"911 Engine are more prone to leaking than other water cooled engines because of their increased total expansion when warm."

-Wayne

Snowman, Could you run down for me all of the places where you used RTV silicone on your motor? :cool:

RTV used on following:
1. Round oil pan cover on bottom of engine
2. Both front and bottom chain cover gaskets
3. breather cover on top of engine
4. on outside of two rocker arm shafts, that looked suspect, ie had some damage to shaft bores. This is in addition to using rocker sealing rings from Andial. Note: this will make removing these two rocker arms a very painful experience.

Pre-formed, aircraft grade, silicone valve cover gaskets.

1-3 is okay in my opinion - as long as it's not gooped on. I would personally use something lighter like Curil-T, rather than silicone.

If you have trouble with cam towers that are so scored, they won't hold even with the RSR seals, I would suggest getting new ones...

-Wayne

Wayne, don't you sell the silicone valve cover gaskets?

A mechanic friend of mine uses RTV in the #4 case. I suspect his customers would rather have the leak go away for an hours labor than pay to have their cam towers replaced.

I'm not a fan of RTV but lets be realistic here, not everyone wants to have every engine mating surfaces lapped and trued to fix leaks. Some RTV used judiciously is a solution even if it isn't the Right Way.

-Chris

ever seen RTV goobered on a cam tower to stop a leak? it's generally wet with oil. basically very poor sealing ability when just goobered on, and looks very un-professional.

My friend uses it in the ends of the rocker shaft, in the hole.
I've worked on a few "leakers" that people had tried to stop leaking by slobberying RTV in various locations. You're right, it didn't stop the leaks.
-Chris

I have an engine with a cam tower leak (actually both sides). I was thinking some type of Dow Corning sealant injected with a syringe. Either that or remove the engine. Any thoughts JW?

-Wayne

heads to cam towers, i would disassemble and reseal. generally hard to tell exactly where they're leaking, and topical ointments don't usually work, (and look "backyard"). rocker shaft leaks, are anything from tightening them more, add "o" rings, or replace the towers if the shaft bores are toast, as you know.

Once there is oil on the surfaces your are sorta out of luck. Its really really hard and may be impossible to remove all the oil without taking it apart and putting it in the hot tank. Thats why I chose the pre emtive strike ( actually the 3 rd teardown for oil leaks).

Note I did not actually put RTV on the round part of the rocker shaft. I first assembled the rockers, just like normal, then I ran a complete bead of RTVaround the on outside of the shaft, sort or plugged the hole,so to speak. If there is oil there I do not think the RTV will stick well enough to seal. IT is a last ditch effort and better than scapping the cam tower, at least in my opinion. By the way the shafts were not damaged seriously, just small lateral grooves in a couple of bores, the kind of groove that can leak but otherwise is immaterial. No scoring or damage like that.

How do rocker shaft bores get to be toast in the cam towers when it is not a moving part? (The shaft+cam tower). Just from the spreading force of the expanding shaft? Just curious. :cool:

Denis,
If a PO/M *forced* them out (the expansion bolt not fully unscrewed), the bore will be galled/scored and prone to leak.

also, if they have been run loose, or if one slipped out and the engine was run for a while with it just hanging on one side, the bore, even though still smooth looking, can be too large for the shaft to expand and get a proper grip, or ovaled, so it would leak.

Update:
The engine is still leaking oil out the spigot bores(left bank) after five minutes of running. There is one bit of information that I forgot to mention before. The engine is using early C2 turbo pistons and cylinders. On disassembly, the engine had the copper base gaskets and was not leaking there before. The only work done on the case was removal of the devlar studs and replacement with factory steel studs. Deck height on all the cylinders is the same according to the factory markings. The right bank is not leaking, but is damp to the touch. It almost looks like a "wick effect". This is really getting to me!! I am a pro at engine removal and tear down, but this is not what I want to put on my resume! ;-)
John Walker, have you seen anything like this before?
Thanks everyone for your invaluable assistance.

"Deck height on all the cylinders is the same according to the factory markings."

I believe that would be the cylinder height marks on the cylinders, not deck height. They have to be the same, otherwise the clamping force is different on each cylinder.

FWIW, if you don't check, you'll never know. What takes more time, R&Ring the drivetrain/taking off the top end or checking cylinder height? You should never leave anything to chance, if at all possible.

Sherwood

Dave,
Do you suppose there might be a nick/bump in the seating surface someplace?
When I assemble a motor, I bolt the heads on individually using the camcarrier as a holding fixture to make sure everything lines up. I torque the heads down and pull off the cam carrier. Then I put a straight edge across the tops of the heads to check that the heights are even.
On the bright side, you are probably learning stuff that you wouldn't if everything had gone together smoothly.
-Chris

Sherwood,
Let's use some logic here.
1.) The spigot bores were not leaking before. The case was split to install new rod bearings and mains and to reseal for a minor case leak.
2.) The leak is consistent across the banks. 1-3 leak and 4-6 are damp. This is not a symptom of cylinder height(thanks for the correction) mismatch, but something else.

Chris,
I used the technique as described in Wayne's recent book. Install the install the heads, hand tighten barrel nuts, install cam tower, torque down, install camshaft in tower, torque head studs(two step), check camshaft for free rotation.
Again, if it were a clamping issue, wouldn't one of the cylinder spigots be dry and the others on that bank be wet? All the spigots are leaking on the left bank. That's what makes this so confusing.

Dave,

Like Sherwood, I didn't realize the nature of your leak (all cylinders) so my post was a off target.

The pros have everything machined so it is flat. I know decking the case is standard operating procedure for at least one well known engine builder. I've been burned by this before so now I check or deck the case (or both). I think there are other advantages to doing the heads and cam carrier separately but I think I'm probably in the minority.

Did you save the old base gaskets? I wonder if they were coated in sealant by the previous engine builder? I wonder if there is some sort of difference between the C2 cylinders and the stock ones? I've got lots of Curil-T if you need it...

I feel for you, this must be pretty frustrating. Believe me, BTDT.
-Chris

Chris,
I am beginning to think that the tower could be masking the issue. One cam tower was machined because of a very small discrepancy on the mating surface. I can't say that this is the cam tower associated with the left bank, but.... if the machining was done in such a manner that the mating surface is no longer square with the heads, it would cause a clamping force issue where there is more force on the top end than the bottom or vice-versa. When the heads are torqued down after the towers, this would exacerbate the issue, giving the cylinders unequal clamping force.
I am sorry to say I did not save the old base gaskets or even to think measuring their respective thicknesses....rookie mistake!:confused:
There are differances in the early C2 turbo cylinders versus the standard 3.3l 930 cylinders. The C2 turbo cases stud bosses were built up to mate with the stud boss area of the cylinder. This added more rigidity to the surface area. The cylinders are also fully finned, top and bottom for additional cooling. I spoke to EBS Racing earlier today and they stated that the C2 turbo cylinder upgrade is a common one. They stated to use the 930 base gaskets in this upgrade, which is what I had done as well as the previous owner had done. EBS had stated they have had no issues with leakage using this technique.

Dave,
I don't think the cam tower(s) could cause this. Long before the tower would cause clamping problems you would experience cam binding I think.
Believe it or not, things could be worse. Today I talked with a guy who heard his 930 motor go boom and then it dumped a lot of oil. He parked it and hasn't had the heart to looked at it yet.
-Chris

It is possible that there were thicker than stock base gaskets on the cylinders. E.g. 0.020" thick vs stock 0.010" or even thicker ones or possibly a pair of thicker ones. Check of piston clearence, cylinder height or compression ratio should answer this question. If the piston were to get to close or make contact it could cause a leak. Not likely for any of this to happen in my opinion but may be worth checking. What else is there???

Did you put some 574 on both sides of the base gaskets like I recommend?

A problem with clamping force would result in at least one cylinder clamping correctly - having all three leak is suspect.

Perhaps the case was disturbed when the studs were replaced? It's not uncommon for the aluminum/magnesium to get slighly pushed out when installing studs like these. Perhaps the cylinder spigots are no longer flat (not uncommon)...

-Wayne

Good point Wayne, Dave, was the case decked? IE the cylinder surfaces redone? Between normal case gyrations and replacing the studs its quite likely the problem is that the cylinder bases are no longer flat and perpendicular to the crank and all on the same plane and orentation.

Personally I do not like using anything under Copper gaskets. To me its sort of like silicone is to most everyone else, something you shouldn't do. And if you need more than the copper can do, then you need to machine it.

Update:
Just measured deck height on cylinder #1. Removed cylinder heads of left bank and found true TDC by mounting dial indicator on center of piston. Z1 is very, very close to true TDC, btw. Measured deck height on number 1 is .040(1.016mm). I suspect this is too low because the head was not torqued down to the cylinder which would have decreased deck height even more by a few thousandths. It is pushing the limits to begin with so I'm going to swap out the .25mm with .50mm shims. Or should I stack .25mm AND .50mm for .75mm total shim space? What do you think?

I measured 1mm (.04") of deck height on my 3.2L. A couple of years back I posted back and forth with Steve Weiner on Rennlist and he said this about deck height:
"Get that CR down to something reasonable without losing deck height. Anything more than .040 is nfg. I like .035 as this leaves less pockets of end gasses out there at the piston edge. This is always where it begins."
-Chris

Interesting Chris.
I went ahead and measured the other two cylinders and found the following;
Deck Height
#1 - .040 (1.016mm)
#2 - .031 (0.787mm)
#3 - .034 (0.864mm)
Nearly a ten thou variance! Can it be that the .25mm shim does not have enough "crush" variance that this type of deck height variance can't be compensated for?

Deck height (top edge of piston to top edge of cylinder) is a tricky thing to measure in my limiited experience. It could mean some cylinders are higher than others or some rods are shorter or a combination of both.
I'd put a straight edge across the tops of the cylinders or (better) the bolted down heads to check. I'm working at home this afternoon if you need to borrow one.
-Chris

you really need to precision measure the cylinder heights. just straightedging them, untorqued is a waste of time. also measure the thickness of all the heads, with a large micrometer, between the cam tower surface and the cylinder contact surface. they may have been flycut inaccurately in the past.

Copper gaskets can soak up maybe 0.001 to 0.005" and this is stretching it a lot. THe cylinders must be within about 0.001"max. this is very difficult to measure accurately. If you are seeing 0.010" differences it is probably real to some extent, way way out of spec.

The cylinders can be measured directly with micrometers, or with a drop guage on some kind of marble table. The case must be measured as well. This is not likely within the scope of any home measurement capability. I would suggest taking the whole thing to someone like CE or Ollies and have them check it and fix it. This is one that really requires a true machine shop to do, a Porsche machine shop.

I put a motor together that should have beene decked and it didn't leak. It wasn't aware of how bad it was until I had that motor apart again and checked it.
Like I said You can tell if they are different heights and if they are tilted that way. Perhaps I should have said "torqued down" instead of "bolted down" but that's what I meant.
-Chris

Update:
1.) Went back and measured all deck heights 1-6. Variances between all cylinders; .031-.034". I suspect that the reason why cylinder 1 was off reading a higher value before(.040") was due to the dial indicator may have not been mounted securely enough.
2.) Tore engine down to the case. Diassembled heads to cam towers. Inspected cam tower sealing area. Found some Locktite 574 had seeped into one of the dowel pin bores for head #2. This created a hard locktite plug which may have had some influence in the alignment of head #2 to the cylinder bore.
3.) Replaced the blue silicone thru-bolt seals with the green viton seals. These are a tougher material seal and I would strongly suggest to anyone doing a rebuild to use these seals. Also, as mentioned in Waynes 911 Rebuild book, the thru-bolt/nut orientation may not be that important. I would strongly advise that the nuts be located on the right side of the case. I installed mine on the left. I inspected the thru-bolt bores and found the right side of the case has the bores chamfered while the left does not. When torqueing a nut and bolt assembly, I have always tightened from the nut side, which in this case, may have been pushing my luck in terms of the seal staying in its seated position. If the washer turns ever so slightly, the likelyhood of that seal kinking or tearing is very high because of the sharp edges on the left side of the case. If done from the right side, the bore is chamfered reducing the possibility of that happening. I don't know if other cases are like this. I am only referring to the 930 case.
4.) Installed .5mm base gaskets instead of the .25mm. This will bring the deck height to a more thermally acceptable value of .04x". I did not use Locktite 574 to seal these gaskets. Instead, I used a Copper based adheasive as a sealer. I spoke to three engine builders and they informed me the copper base gasket acts as a heat sink between the case and the bore. This may not be as important on a NA 911 engine, but with a turbo, I wanted to get as much heat transferred out of the cylinders as possible.
After all of the mods, the bottom line is NO MORE LEAKS!!!http://www.pelicanparts.com/support/smileys/clap.gif

I suspect the most likely scenarios with this leak fiasco are items 3 and 4, with 3 the most likely.
Thank you all for the posts. They gave me a lot to think about. http://www.pelicanparts.com/support/...s/beerchug.gif

High and Dry!!
http://forums.pelicanparts.com/uploads/930underside.jpg

I don't think that those chamfers you are talking about are stock - it's common to spot-face the through-bolt holes flat...

-Wayne