Ed Scherer

I'm currently in the process of acquiring all the parts to update my '90 S4 to use 93-95 GTS cam cover breathing. Cam covers are at the powder coaters right now and probably won't be back for another week or so, so I've got some time to think about what all it's going to take to finish the breathing update.

After reviewing a number of previous threads on the topic (e.g., Valve Cover etc queries; e.g., GTS Breathers -- Where do they go?), I'm still not 100% confident in some stuff related to the adapter elbows and why they changed with the 93 GTS MY. Even though I've already gotten some advice (including some in one of those above-mentioned threads), I'd still like to understand this stuff better.

First, a quick review (and please correct me if I'm wrong on any of this). Here's illustration 103-05, which is used for all 87-95 MYs. The adapter elbows in question are #26 and #27. The two cam covers are identical parts.



Some facts (as best as I can determine):

• #26 is keyed (on the flange) to fit in the right-hand-side hole in a cam cover.
• #26 is part number 928.107.733.02 for MY 87-95.
• #27 is keyed (on the flange) to fit in the left-hand-side hole in a cam cover.
• #27 is part number 928.107.733.00 for MY 87-92, but changes to part number 928.107.733.01 for MY 93-95.
• For MY 87-92, right-side cover (passenger side in U.S., i.e., cylinders 1-4) used a .02 elbow in the right side hole and a .00 elbow in the left side hole. Left-side cover (driver side in U.S., i.e., cylinders 5-8) used a plug in both holes.
• For MY 93-95, right-side cover used a .02 elbow in the right side hole and a .01 elbow in the left side hole. Left-side cover used plug on the right side hole and a .01 elbow in the left side hole.

Other comments:

• I believe that the correct way to upgrade to 93-95 GTS breathing is to (among other things like hoses, which is beyond the scope of this post) change the adapter elbow in the right-side cover left hole from a .00 to a .01 elbow and also to change the plug in the left-side cover left hole to a .01 adapter elbow.
• I've seen recommendations to ("while you're in there") to also change the plug in the left-side cover right hole to an adapter elbow (.02, I'd guess, since that's the only one that's keyed properly?) even if it's just capped for now in case you want to plumb it for more breathing later.
• I suppose it would be nice to stick an "oil separator" tube (928.107.731.01) under the left-side cover right hole (same as the rear hole on the right-side cover), but that part is NLA.

I recently ordered two .01 adapter elbows, but what I got were (in an opened bag, so I'm not sure what really happened) two .02 elbows even though the bag was marked .01.

Now, one thing I'm really curious about is what the differences are between these adapter elbows, aside from the keying that makes them suitable for the left hole or right hole in a cam cover. I've never seen a .01 elbow, but can provide details on the .00 and .02 elbows.

The only other difference I can see (aside from the keying) between a .00 and a .02 is the that .00 is necked down (restricted) on the inside and a .02 is not.

A .00 elbow looks like this:







A .02 elbow looks like this:








Here's a cam cover, where you can see how the left and right breather holes are keyed:





So (finally!), my questions are:

1. What is the difference between a .01 elbow (used on the 93-95 GTSes) and a .00 elbow? Does the .01 have the restriction (necked down) inside like the .00?
2. I've heard that the "left-side-keyed elbows" (e.g., .00 or .01) are hard or impossible to get, and perhaps that's why I got .02 elbows when I ordered .01 elbows. Anybody care to confirm that?
3. I'm considering taking my new existing .02 elbows (that were sent to me instead of the .01 elbows I ordered) and modifying them for use in the left side hole in a cam cover (i.e., "turning a .02 into a .01"). As far as I can tell, this could be as simple as just cutting/filing a new key on the opposite side of the current key. Is there any reason not to do this?
4. Does anyone have any other insight into the whole design intent of the different adapter elbows?

borland

Take a look at the three notes on WSM volume 1A, page 24-218. 'Throttle bores are relocated and deleted'.

borland

Also, find another parts supplier. Some stuff takes time from Germany.

ptuomov

If you are hotrodding 9not restoring) your GT, I suggest putting the tubes and elobws to all four ports and then breathing out of all of them into a pro-vent catch can. Jim Morton set up my low-compression engine that way with four splash-guarded ports breathing out. He also has a method of breathing out the filler neck in a way that (a) works (b) looks factory. Perhpas contact him before proceeding?

Ed Scherer

Excellent! Thanks! Somehow, I missed that. For the record, the notes on this page "Modified breather for crankcase and cylinder heads" are:

1. Oil filler neck: de-icer valve is deleted.
2. Hose connection between oil filler neck and throttle body modified, throttle bore — Ø 5mm — for this breather hose is now located in the oil filler neck.
3. Additional breather hose between right-hand and left-hand rocker cover, throttle bores in the rocker cover for cylinder nos. 1 to 4 are deleted.

That same page also includes a diagram similar to the right part of this one originally posted by ZEUS+:



So... that tells me that a .02 and a .01 are pretty much the same, just keyed differently for left or right hole use.


Supplier is great; this was part of a big order, about 30 or 40 line items. I don't anticipate any problems getting this sorted out. Same supplier managed to get me a fuel rail amazingly quickly, even though it came from Germany.

But... I have heard that the .01 elbows are (or at least were) hard to get.

We'll see.

I just wanted to understand what was going on with these adapter elbows and the design intent of the changes.

Ed Scherer

This is a street car; I might do something fancier later, but I just wanted to improve it a little for now and at least get the elbows in for possible later upgrades.

And... I also wanted to leave some information here that documents for future use the differences between the .00/.01/.02 adapter elbows.

I guess I would be interested to know if there are any readily-available baffles (like the original "oil separator" tube 928.107.731.01, NLA) that could/should be used under each elbow. I don't think I'd want to kluge anything there, though, that could possibly break and drop into the cams.

928mac

Is this the best place to order all of the breather hoses or can Roger get them

ptuomov

Since you have the valve covers off, I would do what Jim did to my low-compression engine. If you know him, you know it's not "kluge. ;-) Four breather ports, all set up with the oil separators and elbows for breathing out. Oil separators are available used for $27 each from wreckers. You'll then have the flexibility to breath out of or into any of the ports.

Currently, with the stock engine, I am set up to breath in from two ports and out of two ports. The low compression engine will be set up to breath out of all four ports.

Ed Scherer

I didn't mean to imply that someone else's work was a kluge, just that I didn't want to fab something myself unless it's really simple and bulletproof. You know, like using hole saws (pretty much the right shape, but probably not the right material ) or something.

Alan

Ed,
All 4 of mine are "variants"... I had them "re-keyed" for approx 40 degrees up & back cant as part of my rework.

Pretty easy to adapt any of them - bit of grinding...

Alan

ptuomov

My work is often a "kluge," but Jim's is not. ;-) In any case, since you have the valve covers off, why not do things in a way that maximizes the flexibility down the road? That is, splash guards on all four ports and elbow out of each one of them.

Ed Scherer

Sounds like a good idea. I'll see what I can turn up on the "splash guards" / "oil separators" / "baffles" / "#36" / "whatever the hell they are". The original parts appear to be NLA new, but perhaps one of our favorite vendors has some used ones.

Leon Speed

When I ordered 01 elbows for this mod, I also received 2R elbows in a sealed 01 bag. Apparently 2R is a casting mark, not part of the part number.

I couldn't get an elbow slotted for the left front drivers side either, but it's easy to key them with a dremel.

The 2R's are not restricted, so good to use.

Hilton

They are not keyed for either side.

If there was a left versus right side, then they'd be 928 107 733 02 and 928 107 734 02 (9th digit odd or even in a Porsche part number indicates left versus right on the car).

Also, if you look at the two cam covers, you'll see that they're set up with the nub on the opposite side of the hole on each cam cover, so a single elbow will fit on either left or right cam cover.

The incremented final digit just indicates a revised part with minor design changes, but is directly compatible with earlier parts that share the same first 10 digits.

edit: Hmm, comments about re-keying to fir other side have me questioning what I thought I saw last time I looked at it.. will have to go have a look at the 32V engine on a stand in my garage and check again - however my comment about left versus right part numbers still stands - its a Porsche convention for all part numbers.

Hilton

My mistake - they are indeed keyed.

I just didn't notice that one of my spare elbows has two key-way slots on it when I checked to see whether they'd fit the 5-8 side on my S4's covers. One of my spares has a slot on both sides of it, so it can fit in any location. (they came off an early 32V engine)

I guess I got lucky with my elbows I'm planning on putting breathers on all 4 ports when I swap my cams.