Thru-Case Bolt O-Rings...am I OK???

[Wayne 962]

Let me re-echo my comments: - The factory didn't use silicone on these spot holes. The engine cases were new then, though, and weren't stressed like they are now. People have to remember that most factory procedures and recommendations are for *new* engines only. - These holes have leaked in the past, due to pinching of the o-ring, or lack of spot-facing, or a spec of dirt, or heat from a cylinder interfering with the seal - etc. etc. etc. - Adding the silicone is an added measure that helps to seal this potentially troublesome area, particularly on rebuilt (not new) engines. As I mentioned previously, Tom Woodford (my technical editor) has used this method on hundreds of engines without any leaks (yes, literally hundreds), therefore, he convinced me it was an applicable procedure to include in the book. Is it really a matter of opinion, but based on what I've heard from people, the extra silicone provides some protection against a bit of dust getting in there, or an o-ring getting pinched, etc... -Wayne

[john walker's workshop]

i use the green viton o rings because they're tough. the wimpy blue silicone ones are often seen squeezing out from under the thru-bolt washer. the majority of the o ring is still where it should be, but the edges get pinched and squeezed flat. makes me nervous. never use the blue ones on a C2/C4 engine, or you may have a multiple day teardown ahead of you. different style of washer on the 3.6. kind of T shaped. the inner sleeve of which, squeezes the o ring against the bore in the case.

[Bobboloo]

That's a good point Wayne. Especially if your through bolt holes are oblong and out of spec. This would diffenently create a problem for an O-ring that was designed for a "new" case.

[Porsche_monkey]

One more point on facing; I just did my own case and the face ran out at least .005" over that small diameter. It definately was not flat when I started, spot facing must help prevent leaks, and once your set up to do case-savers it only takes about 10 minutes.

[Rot 911]

John, where can you get the green viton "O" rings?

[snowman]

I just spent a bit of time with the rep for Felpro, one of the biggest gasket mfgs in the world, discussing head gaskets. The discussion is relavent to this thread because we were discussing OEM VS AFTERMARKET gaskets. The subject-- Why oem gaskets are differen't than aftermarket.

OEM gaskets depend on pristene conditions. Virgin metals and machined surfaces in perfact condition and under perfact controlled conditions.

Aftermarket gaskets are specifically designed for used engines, less than perfact surfaces and much less perfact conditions.

The main point is: What the factory did DOES NOT APPLY to rebuilding an engine!

One can be stubborn, and do it BY THE BOOK, and end up with a leaky engine.

ON the other hand one can recognize what you have at hand, make the necessary accomadations and do something that will work, always, not just sometimes.

Any good gasket mfg can supply viton o rings that will work, just look in the Thomas Register index or search on line.

[WERK I]

The viton o-rings are available from EBS(Engine Builders Supply, Sparks Nevada). Maybe Wayne can get them, too. I haven't seen them in the Pelican Parts Web, but I am sure Wayne has seen them.

[Porsche_monkey]

Any bearing house will be able to get them, you just need to give the ID and thickness

[john walker's workshop]

i got several hundred from charlie wrightwood, wrightwood racing. 805 385 7191. don't think they're into selling small quantities though. maybe.

[cowtown]

Mcmaster-Carr also sells Viton seals in the correct size. I got 100 of them for $5, I think. No leaks after 1000 miles on my 930 (no sealer used either).

[snowman]

I got the ones I used from "Apple Rubber Products Inc" 1-800-828-7745, www.applerubber.com

The quantity used for a single engine is so small that they would most likely be supplied as a sample, as the order would be to small to bother with. This is a case where someone like Wayne can help. IE buy enough to make a real order, ie a couple of hundered dollars and supply the Porsche world for the next 20 years with what he got for that price. Even though a single engine may only represent a few cents worth of o rings, I am sure it is worth $5 or $10 bucks to us to have them available as seperate items.

I have personally used both the silicone and viton o rings. The viton ones are much better and do not get buggered up as easily. No extra silicone should be used, just a lot of oil.

PS

in support of Wayne, if you use the silicone o rings, use extra silicone like Wayne suggests. Just don't do it with Viton ones.

[Doug Zielke]

Originally posted by snowman
OEM gaskets depend on pristene conditions. Virgin metals and machined surfaces in perfact condition and under perfact controlled conditions.

Aftermarket gaskets are specifically designed for used engines, less than perfact surfaces and much less perfact conditions.

The main point is: What the factory did DOES NOT APPLY to rebuilding an engine!

That's just pure nonsense!!!

I always have used OEM gaskets on every automobile, motorcycle, and marine engine I've rebuilt/repaired.

Regardless of 'perfact' surfaces (more BS) or not, the OEM gaskets never leaked a drop!

Certain aftermarket gaskets may be of equal quality, but I've never found any of them to be better than OEM.

No more of this rubbish, please.

[snowman]

Well according to the lying bastards that make them they make the aftermarket ones completely differen't to account for what the average rebuilder runs into.

the head gaskets have more layers, they also can comply with rougher surface finishes. Other gaskets are also differen't. They do this (according to the lying reps) to help rebuilders make a better product and get less comebacks. Felpro is only a multi billion dollar company so they may not represent what everyone else does.

[john walker's workshop]

we're into 911s here. no layers in the head gaskets. never seen any felpro gaskets for porsche in fact. wrong forum.

[snowman]

The whole point is that things change. The reason Felpro makes differen't gaskets for the rebuild market is that the engines are NO LONGER virgin metal. They are really differen't. Porsche is no exception. Remanufacturing engines require differen't stuff than oem stuff, thats a PROVEN FACT. Anyone who thinks differen't is fooling himself.

PS

An exception MAY be Porsche head gaskets, just because of the unique nature of them. On the other hand I do not know if some people experience trouble with some of them, if they do there may be a reason.

[cowtown]

I dunno Snowman.

The logical conclusion to be drawn from your argument is that aftermarket gaskets beat OEM when we're rebuilding our engines.

That's the first time I've heard this, and it's a gamble I wouldn't be (and was not) willing to take. About the "virgin metal," thing: The metal has been cleaned and mating surfaces should be true, so I just don't see the aftermarket argument holding any water.

Colin

[snowman]

The main argument presented by the rep was that aftermarket machine work often ends up with a rougher surface finish, ie 60 micro inch vs 20 micro inch for oem. this is mostly due to the much less expensive machines the aftermarket can afford vs the really state of the art stuff the factory has. This surface finish is CRITICAL to proper gasket sealing.

Gaskets that can seal a 60 micro inch surface finish are differen't than ones that can seal a 20 micro inch finish.

A good example is a water cooled V8 with a cast iron block and Aluminum heads. OEM head gaskets can get away with single layer, almost conventional head gaskets. Aftermarket head gaskets, ones that can sucessuflly seal the very same heads require up to 6 layers of metals combined in a way that will allow expansion in 3 dimensions and still remain sealed. Putting this in terms that are easier to understand, aftermarket mfgs buy head gaskeets that may cost $100 ea vs $10 for OEM. Why would the cheepest people in the world spend this much money? Because they HAVE to.

PS

Your Porsche may in fact have some Felpro stuff in it. It may be a differen't name, but the same company.

[ChrisBennet]

Originally posted by snowman
I just spent a bit of time with the rep for Felpro, one of the biggest gasket mfgs in the world, discussing head gaskets. The discussion is relavent to this thread because we were discussing OEM VS AFTERMARKET gaskets. The subject-- Why oem gaskets are differen't than aftermarket.

OEM gaskets depend on pristene conditions. Virgin metals and machined surfaces in perfact condition and under perfact controlled conditions.

Aftermarket gaskets are specifically designed for used engines, less than perfact surfaces and much less perfact conditions.

The main point is: What the factory did DOES NOT APPLY to rebuilding an engine!

One can be stubborn, and do it BY THE BOOK, and end up with a leaky engine.

ON the other hand one can recognize what you have at hand, make the necessary accomadations and do something that will work, always, not just sometimes.

Any good gasket mfg can supply viton o rings that will work, just look in the Thomas Register index or search on line.

This gasket info is probably more applicable to non-911 engines but what Jack's main point that what the factory did/does may be different than what a rebuilder does is true IMO.

The factory manuals makes no mention of RSR rocker shaft seals yet we all use because we know the rocker shaft bores aren't "like new" anymore. Wayne's "silicone on the through bolt o-rings" trick is another example. I don't remember if the factory manuals saying anything about decking case spigots but there again, we do it because we recognize things change.

I realize disagreeing with Jack provides a bit of fun for some of you but I think it might be wiser to consider what he said. In my case I can't think of a 911 application for the gasket info he got from the Felpro guy but I mentally filed away that aftermarket rebuild gaskets may be different than OEM for future reference on other motors.

-Chris
"If I'm the voice of reason here, we're in trouble."

[jgparker]

I don't know guys, I've seen a lot of leaky OEM lower valve covers gaskets on 911s. I've also seen a few non-OEM gaskets that do a much better job of sealing them up. Keep in mind, absloute satements are almost always wrong, like aftermarket gaskets can never be better than OEM, or all retired RF engineers are idiots. I think we need a group hug.

[Porsche_monkey]

Just to return to the O-ring issue, it appears to me that this is a metric O-ring, it is bigger than a standard 011 but smaller than a 012.

Anyone know the metric generic part number, I think it's 8mm bore x 2mm thick ?